ISO/FDIS 14505-2

Ergonomics of the thermal environment — Evaluation of thermal environments in vehicles — Part 2: Determination of equivalent temperature

ISO 14505-2:2006 provides guidelines for the assessment of the thermal conditions inside a vehicle compartment. It can also be applied to other confined spaces with asymmetric climatic conditions. It is primarily intended for assessment of thermal conditions, when deviations from thermal neutrality are relatively small. Appropriate methodology as given in ISO 14505-2:2006 can be chosen for inclusion in specific performance standards for testing of HVAC-systems for vehicles and similar confined spaces.

Ergonomie des ambiances thermiques — Évaluation des ambiances thermiques dans les véhicules — Partie 2: Détermination de la température équivalente

L'ISO 14505-2:2006 donne des lignes directrices relatives à l'évaluation des conditions thermiques à l'intérieur d'un habitacle de véhicule. Elle peut également s'appliquer à d'autres espaces confinés où règnent des conditions climatiques asymétriques. Elle est essentiellement destinée à l'évaluation des conditions thermiques, lorsque les écarts par rapport à la neutralité thermique sont relativement faibles. L'une des méthodes appropriées décrite dans l'ISO 14505-2:2006 peut être choisie pour être incluse dans des normes de performance spécifiques en vue d'essayer les systèmes de chauffage, de ventilation et de climatisation (système CVCA) des véhicules et les espaces confinés analogues.

General Information

• Status: Not Published
• ICS: 13.180 - Ergonomics
• ICS: 43.020 - Road vehicles in general
• Technical Committee: ISO/TC 159/SC 5 - Ergonomics of the physical environment
• Drafting Committee: ISO/TC 159/SC 5 - Ergonomics of the physical environment
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 24-Apr-2026
• Completion Date: 24-Apr-2026

Relations

• Consolidates: FprEN ISO 14505-2 - Ergonomics of the thermal environment - Evaluation of thermal environments in vehicles - Part 2: Determination of equivalent temperature (ISO/FDIS 14505-2:2026)
• Effective Date: 12-Feb-2026
• Consolidates: ISO 6183:2009/Amd 2:2019 - Fire protection equipment — Carbon dioxide extinguishing systems for use on premises — Design and installation — Amendment 2
• Effective Date: 13-May-2023
• Revises: ISO 14505-2:2006 - Ergonomics of the thermal environment — Evaluation of thermal environments in vehicles — Part 2: Determination of equivalent temperature
• Effective Date: 29-Apr-2023

Overview

ISO/FDIS 14505-2, titled Ergonomics of the thermal environment - Evaluation of thermal environments in vehicles - Part 2: Determination of equivalent temperature, is an international standard developed by ISO. This document provides comprehensive guidelines for assessing thermal conditions inside vehicle compartments, focusing on the determination of equivalent temperature. Its applications extend beyond vehicles into other confined spaces where asymmetric climatic conditions may exist. The methodologies set out in ISO 14505-2 are especially useful for scenarios where deviations from thermal neutrality are relatively minor. The standard also offers procedures that can be incorporated into performance standards for testing HVAC systems in vehicles and similar environments.

Key Topics

• Thermal Assessment Principles: The standard details the principles and procedures for quantifying the thermal environment using equivalent temperature, a unified metric combining convection and radiation effects on human heat exchange.
• Equivalent Temperature Types:
  • Whole body equivalent temperature: Measures overall thermal conditions affecting the body.
  • Segmental equivalent temperature: Assesses specific body segments (e.g., head, chest, limbs).
  • Directional equivalent temperature: Evaluates heat exchange in particular orientations with flat sensors.
  • Omnidirectional equivalent temperature: Uses ellipsoid sensors to measure combined directional factors.
  • Equivalent contact temperature: Focuses on heat flux between the body and contact surfaces-critical for vehicle seats.
• Instrument Guidelines: Recommends appropriate measurement devices, including thermal manikins, omnidirectional sensors, and flat heated sensors, complete with calibration and specification requirements.
• Assessment Methods: Provides step-by-step procedures for conducting local and whole-body thermal measurements, interpreting results, and ensuring repeatability and accuracy.

Applications

ISO/FDIS 14505-2 serves a wide range of professional and industrial needs, including:

• Vehicle HVAC Testing and Design: Automakers and HVAC engineers can use these guidelines to evaluate cabin thermal comfort, optimize climate control systems, and comply with regulatory requirements.
• Cabin and Confined Space Comfort Analysis: The standard’s methodology is applicable to trains, aircraft, marine vessels, and specialized work environments, ensuring occupant comfort and safety in varied conditions.
• Ergonomic Product Evaluation: Researchers and developers of seats and interior components can assess the impact of materials and designs on localized thermal comfort, especially in areas of direct skin contact.
• Regulatory Compliance and Performance Benchmarking: By following a unified approach, organizations can demonstrate compliance with health, safety, and ergonomics standards pertaining to thermal environments in transportation and industrial applications.

Related Standards

To support a holistic approach to assessing the thermal environment, the following standards are often used alongside ISO/FDIS 14505-2:

• ISO 14505-1: Ergonomics of the thermal environment - Evaluation of thermal environments in vehicles - Part 1: Principles and methods for assessment of thermal stress
• ISO 14505-3: Ergonomics of the thermal environment - Evaluation of thermal environments in vehicles - Part 3: Evaluation of thermal comfort using human subjects
• ISO 13731: Ergonomics of the thermal environment - Vocabulary and symbols
• SAE J2234: Recommended practice for measuring thermal comfort in vehicles
• ISO 7730: Ergonomics of the thermal environment - Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices

Practical Value

Applying ISO/FDIS 14505-2 enables organizations to:

• Ensure thermal comfort and safety for drivers and passengers
• Provide objective, repeatable data for vehicle development and certification
• Identify and mitigate local discomfort conditions, especially in asymmetric climatic scenarios
• Advance ergonomic design and occupant well-being through data-driven insights into thermal environments

By leveraging this standard, manufacturers, researchers, and regulatory bodies can achieve efficient, accurate, and user-centered evaluation of vehicle and cabin thermal conditions.

Standards Content (Sample)

DRAFT
International
Standard
ISO/DIS 14505-2
ISO/TC 159/SC 5
Ergonomics of the thermal
Secretariat: BSI
environment — Evaluation of
Voting begins on:
thermal environments in vehicles —
2025-05-01
Part 2:
Voting terminates on:
2025-07-24
Determination of equivalent
temperature
Ergonomie des ambiances thermiques — Évaluation des
ambiances thermiques dans les véhicules —
Partie 2: Détermination de la température équivalente
ICS: 13.180; 43.020
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 14505-2:2025(en)
DRAFT
ISO/DIS 14505-2:2025(en)
International
Standard
ISO/DIS 14505-2
ISO/TC 159/SC 5
Ergonomics of the thermal
Secretariat: BSI
environment — Evaluation of
Voting begins on:
thermal environments in vehicles —
Part 2:
Voting terminates on:
Determination of equivalent
temperature
Ergonomie des ambiances thermiques — Évaluation des
ambiances thermiques dans les véhicules —
Partie 2: Détermination de la température équivalente
ICS: 13.180; 43.020
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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POTENTIAL TO BECOME STANDARDS TO
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or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
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TO SUBMIT, WITH THEIR COMMENTS,
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Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 14505-2:2025(en)
ii
ISO/DIS 14505-2:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Assessment principles . 2
4.1 General description of equivalent temperature .2
4.2 General determination principle of equivalent temperature .3
5 Specific equivalent temperatures . 4
5.1 General .4
5.2 Whole body equivalent temperature . .4
5.2.1 Determination principle .4
5.2.2 Calculation .4
5.3 Segmental equivalent temperature .5
5.3.1 Determination principle .5
5.3.2 Calculation .5
5.4 Directional equivalent temperature .5
5.4.1 Determination principle .5
5.4.2 Calculation .5
5.5 Omnidirectional equivalent temperature .6
5.5.1 Determination principle .6
5.6 Calculation .6
6 Measuring instruments . 7
7 Assessment . . 7
7.1 Determination of whole body equivalent temperature .7
7.1.1 Determination with omnidirectional sensors .8
7.1.2 Determination with a thermal manikin .8
7.2 Determination of local equivalent temperature .8
7.2.1 Determination with omnidirectional sensors or flat, heated sensors .8
7.2.2 Determination with a thermal manikin .8
8 Equivalent contact temperature t . 8
eq,cont
Annex A (informative) Examples of measuring instruments .12
Annex B (informative) Characteristics and specifications of measuring instruments .15
Annex C (informative) Calibration and other determinations .21
Annex D (informative) Interpretation of equivalent temperature .23
Annex E (informative) Examples .27
Bibliography .30

iii
ISO/DIS 14505-2:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 159, ergonomics, Subcommittee SC 5,
ergonomics of the physical environment.
This second edition cancels and replaces the first edition (ISO 14505-2:2006), which has been technically
revised.
The main changes are as follows:
— evaluation method for the contact areas (equivalent contact temperature)
A list of all parts in the ISO 14505 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/DIS 14505-2:2025(en)
Introduction
The interaction of convective, radiative and conductive heat exchange in a vehicle compartment is very
complex. External thermal loads in combination with the internal heating and ventilation system of the
vehicle create a local climate that can vary considerably in space and time. Asymmetric thermal conditions
arise, and these are often the main cause of complaints of thermal discomfort. In vehicles without or having
a poor heating, ventilating and air-conditioning system (HVAC-system), thermal stress is determined
largely by the impact of the ambient climatic conditions on the vehicle compartment. Subjective evaluation
is integrative, as the individual combines into one reaction the combined effect of several thermal stimuli.
However, it is not sufficiently detailed or accurate for repeated use. Technical measurements provide
detailed and accurate information but require integration in order to predict the thermal effects on humans.
Since several climatic factors play a role for the final heat exchange of a person, an integrated measure of
these factors, representing their relative importance, is required. This standard includes the equivalent
temperature models t for the assessment of the thermal conditions. For special consideration of the seat,
eq
the equivalent contact temperature t can be applied for body compartments in contact to surfaces.
eq,cont
v
DRAFT International Standard ISO/DIS 14505-2:2025(en)
Ergonomics of the thermal environment — Evaluation of
thermal environments in vehicles —
Part 2:
Determination of equivalent temperature
1 Scope
This part of ISO 14505 provides guidelines for the assessment of the thermal conditions inside a vehicle
compartment. It can also be applied to other confined spaces with asymmetric climatic conditions. It is
primarily intended for assessment of thermal conditions, when deviations from thermal neutrality are
relatively small. Appropriate methodology as given in this part of ISO 14505 can be chosen for inclusion in
specific performance standards for testing of HVAC-systems for vehicles and similar confined spaces.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 13731, Ergonomics of the thermal environment — Vocabulary and symbols
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13731 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
equivalent temperature t
eq
temperature of a homogenous space, with mean radiant temperature equal to air temperature and zero
air velocity, in which a person exchanges the same heat loss by convection and radiation as in the actual
conditions under assessment
3.2
whole body equivalent temperature t
eq,whole
temperature of an imaginary enclosure with the same temperature in air and on surrounding surfaces and
with air velocity equal to zero in which a full-scale, human shaped, heated sensor will exchange the same
dry heat by radiation and convection as in the actual non-uniform environment
3.3
segmental equivalent temperature t
eq,segment
uniform temperature of an imaginary enclosure with the same temperature in air and on surrounding
surfaces and with air velocity equal to zero in which one or more selected zones of a thermal manikin will
exchange the same dry heat by radiation and convection as in the actual non-uniform environment

ISO/DIS 14505-2:2025(en)
3.4
directional equivalent temperature t
eq,direct
uniform temperature of an imaginary enclosure with the same temperature in air and on surrounding
surfaces and with air velocity equal to zero in which a small flat heated surface will exchange the same dry
heat by radiation and convection as in the actual non-uniform environment
3.5
omnidirectional equivalent temperature t
eq,omni
uniform temperature of an imaginary enclosure with the same temperature in air and on surrounding
surfaces and with air velocity equal to zero in which a heated ellipsoid will exchange the same dry heat by
radiation and convection as in the actual non-uniform environment
3.6
equivalent contact temperature t
eq,cont
uniform temperature of an imaginary contact surface, at room air speed close to zero, at which a person will
exchange the same amount of dry heat through thermal conduction for a virtual clothing insulation as in
the actual non-uniform environment, where the person experiences sensible and latent heat transfer at the
considered body parts
3.7
segment
part of a human-shaped sensor, normally corresponding to a real body-part, consisting of one or several
whole zones, for which a segmental equivalent temperature, t , is presented
eq,segment
3.8
zone
physical partition of a manikin, which is independently regulated and within which the surface temperature
and heat exchange is measured
3.9
HVAC-system
heating, ventilating and air-conditioning system of the vehicle and/or cabin
4 Assessment principles
The assessment principle is based on the measurement of the equivalent temperature. The equivalent
temperature provides a unified, physical measure of the climatic effects on the human dry heat exchange.
On the basis of the actual value for, and the variation in, equivalent temperature, it is possible to predict
the conditions for heat balance under conditions in or close to the thermoneutral zone. People’s thermal
sensation is primarily influenced by general and local levels and variations in skin surface heat flux. Values
for the equivalent temperature of a defined environment have been found to be closely related to how people
perceive thermal conditions when exposed to the same environment. This can be used for the interpretation
of the t value and assessment of the quality of the environment.
eq
The climate is assessed in terms of a total equivalent temperature, which describes the level of thermal
neutrality.
The climate is also assessed for local effects on defined parts of the human body surface. The local equivalent
temperatures determine to what extent the actual body parts fall within the range of acceptable levels of
heat loss (local discomfort).
4.1 General description of equivalent temperature
The equivalent temperature is a pure physical quantity, that in a physically sound way integrates the
independent effects of convection and radiation on human body heat exchange. This relationship is best
described for the overall (whole body) heat exchange. There is limited experience with relations between
local dry heat exchange and local equivalent temperature. The standardized definition of t applies only for
eq
the whole body. Therefore, the definition has to be modified for the purposes of this part of ISO 14505. t
eq
ISO/DIS 14505-2:2025(en)
does not take into account human perception and sensation or other subjective aspects. However, empirical
studies show that t values are well related to the subjective perception of the thermal effect.
eq
4.2 General determination principle of equivalent temperature
Determination of t is based on equations for convective and radiative heat transfer for clothed persons.
eq
Heat exchange by conduction is assumed to be small and accounted for by radiation and convection.
Rh=×()tt− (1)
rskr
Ch=×()tt− (2)
cska
where
R is heat exchange by radiation, in watts per square metre (W/m );
C is heat exchange by convection, in watts per square metre (W/m );
h is the radiation heat transfer coefficient, in watts per square metre degree Celsius [W/(m °C)];
r
h is the convection heat transfer coefficient, in watts per square metre degree Celsius [W/(m °C)];
c
t is the skin temperature, in degrees Celsius (°C);
sk
t
is the mean radiant temperature, in degrees Celsius (°C);
r
t is the ambient air temperature, in degrees Celsius (°C).
a
In practice the equivalent temperature is determined and defined by
Q
tt= − (3)
eq s
h
cal
where
t is the surface temperature, in degrees Celsius (°C);
s
t is the temperature of the standard environment, in degrees Celsius (°C);
eq
Q is the measured convective and radiative heat loss during the actual conditions, in watts per square
metre (W/m );
QR=+C (4)
h is the combined heat transfer coefficient, determined during calibration in a standard environment,
cal
in watts per square metre degree Celsius [W/(m °C)].
The standard environment comprises homogenous, uniform thermal conditions with t = t and air velocity
a r
v , < 0,1 m/s. A suitable calibration procedure is described in Annex C.
a
ISO/DIS 14505-2:2025(en)
5 Specific equivalent temperatures
5.1 General
As there is no method available for measurement of the true total or local t , four specific equivalent
eq
temperatures are calculated according to different principles, according to 5.2 to 5.5. Depending on different
measuring principles, they are defined as
1. whole body equivalent temperature,
2. segmental equivalent temperature,
3. directional equivalent temperature,
4. omnidirectional equivalent temperature.
5.2 Whole body equivalent temperature
5.2.1 Determination principle
The principle of determination is to measure the total heat flow from a human-sized test manikin consisting
of several zones, each with a specific measured surface temperature similar to that of a human being.
Theoretically whole body equivalent temperature can be measured with thermal manikins or a large
number of flat heated sensors attached to an unheated manikin. The accuracy of the result is depending
on surface temperature, size of body, number and division of zones, posture etc. An appropriate method
to use is a thermal manikin divided into separate, individually heated zones covering the whole body, with
surface temperatures close to that of a real human being. A human-sized manikin with only one zone will
not determine a realistic whole body t because the thermal conditions vary too much over the surface. The
eq
more zones the manikin has, the more correct value it will measure.
5.2.2 Calculation
Q
whole
tt= − (5)
eq,whole sk,whole
h
cal,whole
tA⋅
()
∑ sk,n n
t = (6)
sk,whole
A
∑ n
QA⋅
()
∑ nn
Q = (7)
whole
A
n
∑
where
A is a weighting factor based on the surface area;
h is determined by calibration in a standard environment (see Annex C);
cal,whole
n is the number of zones of the body (0 < n ≤ N).
In order to be able to compare results from other manikins, the measured t should be presented together
eq
with specifications of the manikin used, such as regulation principle, skin temperature, number of zones etc.
(see Annexes A and B).
ISO/DIS 14505-2:2025(en)
5.3 Segmental equivalent temperature
5.3.1 Determination principle
The principle of determination is to measure the total heat flow from a segment consisting of one or more
zones, each with a specific measured surface temperature similar to that of a human being.
The segmental t is based on the heat flow from a certain part of the body, i.e. a segment, such as hand,
eq
head or chest. The segmental t can only be measured with a full-sized, human-shaped heated sensor,
eq
e.g. a thermal manikin. The number of zones and the partition between them must at least be such that it
corresponds to the actual segment that the segmental t should be measured for. Some segments, e.g. thigh,
eq
need to be divided into at least two zones within the segment, because the thermal conditions are different
on the front and the rear (seat contact) side in the case of the thigh.
5.3.2 Calculation
Q
segment
tt= − (8)
eq,segment sk,segment
h
cal,segment
tA⋅
()
∑ sk,n n
t = (9)
sk,segment
A
∑ n
QA⋅
()
∑ nn
Q = (10)
segment
A
∑ n
where
h is determined by calibration in a standard environment (see Annex C);
cal,segment
n is the number of zones of the body (0 < n ≤ N).
The segment can be freely chosen, but it must consist of one or more whole zones. Normally body parts
like head, hands, arms, feet, legs, chest, back and seat are chosen. To be able to compare results from other
measurements, the measured t should be presented with specifications about the segment used, such
eq
as regulation principle, surface temperature, which body part, number, size and partition of zones of the
segment (see Annexes A and B).
5.4 Directional equivalent temperature
5.4.1 Determination principle
The principle of determination is to measure the total heat flow from a small flat surface with a measured
surface temperature. The directional t can be described as a normal vector to the measuring plane in
eq
every point, defined by magnitude and direction. It refers to the heat exchange within the half-sphere in
front of the infinitesimal plane. The directional t can only be measured with a flat sensor, which might
eq
or might not be attached to an unheated manikin or other positioning device. Several sensors can be used
simultaneously to determine directional t at other locations or in other directions, provided that they are
eq
positioned so that they do not influence each other.
5.4.2 Calculation
Q
direct
tt= − (11)
eq,directsk,direct
h
cal,direct
ISO/DIS 14505-2:2025(en)
where
t is the surface temperature of the sensor;
sk,direct
Q is the heat flow from the sensor;
direct
h is determined by calibration of the sensor in a standard environment (see Annex C).
cal,direct
A local equivalent temperature, t , can be calculated as an average value from several measurements
eq,local
at the same location but in different directions. It can be calculated as an arithmetic mean value without
weighting factors (equation 12) or with weighting (equation 13) to simulate a certain body posture.
t
∑ eq,direct,n
t = (12)
eq,local
n
where n is the number of directions.
tt= ⋅A (13)
()
eq,local eq,direct,nn
∑
where n is the number of measurements, with Σ(A ) = 1, and A represents body postures.
n
A total equivalent temperature can be calculated as a weighted mean value of local equivalent temperatures.
tt= ⋅A (14)
()
eq,total ∑ eq,local,nn
where n is the number of locations, with Σ(A ) = 1.
n
In order to be able to compare results from other measurements, the measured t should be presented
eq
with specifications about the sensor used, such as regulation principle, surface temperature, size and also
location and direction of the sensor (see Annexes A and B). Whole body t and total t is not the same. In an
eq eq
asymmetric climate and with seat contact the difference between them will be considerable.
5.5 Omnidirectional equivalent temperature
5.5.1 Determination principle
The principle of determination is to measure the total heat flow from the surface of an ellipsoid with a
measured surface temperature. The omnidirectional t can be described as the weighted mean value of
eq
the directional t in all directions. The weighting factors for the different directions are dependent of the
eq
form of the ellipsoid. It refers to the heat exchange in all directions. The omnidirectional t can only be
eq
measured with an ellipsoid sensor with uniform heat flow over the surface. One or more sensors can be used
simultaneously. If more than one sensor is used, it must be pointed out that the sensors will influence each
other as hot surfaces in the sphere that is measured.
5.6 Calculation
Q
omni
tt= − (15)
eq,omnisk,omni
h
cal,omni
where
t is the surface temperature of the sensor;
sk,omni
Q is the heat flow from the sensor;
omni
h is determined by calibration of the sensor in a standard environment (see Annex C).
cal,omni
ISO/DIS 14505-2:2025(en)
Omnidirectional t determined with one ellipsoid sensor in an asymmetric climate is a local t . A total t
eq eq eq
can be calculated as an arithmetic mean value from sensors at different locations with weighting factors for
different body parts according to SAE J 2234.
tt= Σ⋅A (16)
()
eq,total eq,loca,ln n
where n is the number of locations, with Σ(A ) = 1.
n
In order to be able to compare results from other measurements, the measured t should be presented
eq
with specifications about the sensor used, such as regulation principle, surface temperature, size and also
location and direction of the sensor (see Annexes A and B).
6 Measuring instruments
Several measurement methods and instruments, representing different measuring principles, are given in
Annexes A and B. Depending on needs, a method as given in Annex A should be selected.
Measurement values obtained with principally different methods are not comparable with each other. They
represent different levels in terms of
— reliability,
— relevance,
— validity,
— repeatability,
— accuracy,
— integration,
— complexity,
— cost, and
— availability
Performance and requirements of the specific methods are given in Annex B. Requirements for calibration
procedures are given in Annex C.
7 Assessment
The equivalent temperature represents a quantitative assessment of the conditions for physical heat
exchange. The numeric value of t is a temperature level that can come close to “normal” expected room
eq
temperatures. Higher t values indicate lower heat losses (“warmer”), while lower t values indicate higher
eq eq
heat losses (“colder”).
The interpretation of equivalent temperature in terms of anticipated perceived thermal sensation is based
on series of experiments with participants in which the different types of equivalent temperature have been
measured. Examples of interpretation are given in Annex C. For some types of equivalent temperature, data
are not available for comparison with human responses. Nevertheless, these kinds of measurement can be
used for differential measurements of thermal conditions.
7.1 Determination of whole body equivalent temperature
Determination of whole body equivalent temperature should preferably be done with measurements using
a thermal manikin or by integration of discrete measurements using omnidirectional sensors placed at
defined positions in the vehicle cabin.

ISO/DIS 14505-2:2025(en)
7.1.1 Determination with omnidirectional sensors
Omnidirectional sensors are described in Annexes A and B. Sensors are placed on a stand simulating a person
and placed in a seat of the vehicle. At least six sensors are placed in relevant positions and measurements
are made when steady state is achieved. Whole body equivalent temperature is determined as the area-
weighted average of the individual sensors. Interpretation of values should be made according to Annex D.
7.1.2 Determination with a thermal manikin
Requirements for the manikin and procedures are described in Annexes A and B. The manikin is placed in a
seat in the vehicle and whole body heat loss is measured when steady state conditions are achieved. Whole
body heat loss is the area-weighted average of the independent segments of the manikin. Interpretation of
values should be made according Annex D.
7.2 Determination of local equivalent temperature
Determination of whole body equivalent temperature should preferably be done with measurements using a
thermal manikin or by the integration of discrete measurements using omnidirectional sensors.
7.2.1 Determination with omnidirectional sensors or flat, heated sensors
Omnidirectional sensors are described in Annex A. Sensors are placed on a stand simulating a person and
placed in a seat of the vehicle or at defined spots on the surface of the clothing of a person or a manikin.
Measurements are made when steady state is achieved. Local equivalent temperature is determined as the
value of the individual sensor. The more sensors located in the space, the better resolution of the variation in
the thermal field around the human body.
7.2.2 Determination with a thermal manikin
Requirements for the manikin and procedures are described in Annexes A and B. The manikin is placed
in a seat in the vehicle and heat loss is measured from a local segment of the manikin when steady state
conditions are achieved. Local equivalent temperature is determined by the measured value of the individual
segment and represent that particular segment only. Interpretation of values should be made according to
Annex D.
8 Equivalent contact temperature t
eq,cont
The heat exchange between a person and a contacting surface by heat conduction as well as moisture is
not negligible and has a significant influence on the thermal sensation. The calculation of the equivalent
contact temperature t is based on the equations for heat conduction as well as latent and sensible heat
eq,cont
exchange between a clothed person and the contacting surfaces.
As shown in Figure 1, the principles for definition of the equivalent contact temperature t and
eq,cont
equivalent temperature t are similar to each other and both depend on the air velocity v in the real
eq air
environment. In the equivalent temperature model, the equivalent heat flux q depends on the convective
eq
q and radiant heat fluxes q in the real environment with the determined radiant temperature t , air
conv rad r
temperature t and skin temperature t . The equivalent contact temperature t includes the detailed
air skin eq,cont
description of the thermodynamic situation at the contact interface between a seat and the human body
surface. Here, the equivalent heat flux q depends on the combined effect of heat conduction through
eq,cont
the clothing q and the seat q as well as the change in enthalpy due to sensible and latent heat transfer
clo seat
in the real environment, such as by the moisture flow from skin to contact area q . These mechanisms can
evp
be influenced by the use of mechanically induced air flow rates (e.g. seat ventilation, q - q ) or heat
air,out air,in
sources (e.g. seat heating, q ).
heat
This chapter describes an index for evaluating the thermal comfort of seats. This evaluation method is
basically based on experiments with participants, but it can also be applied to evaluations using thermal
manikins, as described in the previous chapter, by replacing the evaporation effects of perspiration on the

ISO/DIS 14505-2:2025(en)
seat contact surface with a theoretical model. This means a suitable theoretical sweating model is available
for evaluating t with a thermal manikin instead of a participant.
eq,cont
Calculation methodology:
As can be seen from Figure 1, the calculation of t is based on the balance of heat flux densities at an
eq,cont
infinitesimal volume element (green area). The equivalent heat flux q (Figure 1b, right-hand side)
eq,cont
depends on the heat fluxes in the real environment (Figure 1b, left-hand side) according to the equations
in the centre of Figure 1b. The volume element is represented by node K at which the energy balance is
performed. Furthermore, K represents the contact interface between the human body and any kind of
contacting surface.
Figure 1 — Definition and physical interpretation of the equivalent temperature (a) and equivalent
contact temperature (b). The t is described using a nodal energy balance at node K (left-hand
eq,cont
side: heat fluxes in real environment, right-hand side: heat flux in equivalent environment with a
calibrated insulation value R ).
calib
The energy balance at node K is described by (17), where negative quantities leave K and positive ones enter K.
q+qq−−+q q+q=0 (17)
cloevp seat air,in air,outheat

ISO/DIS 14505-2:2025(en)
where
q is the heat flux density through the clothing, in watts per square metre (W/m );
clo
q is the heat flux density of the moisture flow through the clothing, in watts per square metre (W/m );
evp
q is the heat flux density through the seat, in watts per square metre (W/m );
seat
q is the heat flux density of the incoming mass air flow by seat fan, in watts per square metre (W/m );
air,in
q is the heat flux density of the outgoing mass air flow by seat fan, in watts per square metre (W/
air,out out
m );
q is the heat flux density of an optional internal heat source, in watts per square metre (W/m ).
heat
The heat flux densities in the real environment, visualized on the left-hand side of Figure 1b are subsequently
described with the heat flux density through the clothing layer q (18), the evaporative heat flux density
clo
between skin and contact area q (19), the conductive heat flux density through the seat q (20), the
evp seat
outgoing heat flux density due to the seat ventilation q (21) as well as the incoming heat flux density
air,out
due to the seat ventilation q (22) and the heat flux generated by the use of a heat source q (23).
air,in heat
tt−
skin nod
q= (18)
clo
R
clo

mr⋅⋅+ct ⋅()xx−
()
da 0 P,vapskinnod env
q= (19)
evp
A
cont
tt−
nodenv
q= (20)
seat
R
seat

mc×+⋅⋅tx (r +ct⋅ )
()
da P,da nodnod 0P,vap nod
q= (21)
air,out
A
cont
mc ⋅⋅tx+(⋅⋅rc+)t
()
da P,da envenv 0P,vap env
q= (22)
air,in
A
cont
A Q
cont el
q= ⋅⋅η (23)
heat
A A
tot tot
where
A is the contacting surface area related to a person’s body, in square metres (m );
cont
A is the total heated seat surface area, in square metres (m );
tot
c is the specific heat capacity of water vapor (= 2 080 J/(kg °C)), in joules per kilogram degree Celsius
p,vap
[J/(kg °C)];
c is the specific heat capacity of dry air (= 1 005 J/(kg °C)), in joules per kilogram degree Celsius [J/
p,da
(kg °C)];

m is the mass flow rate generated by the seat fans, in kilograms per second (kg/s);
da
Q is the electrical power consumed by the seat heating, in watts (W);
el
r is the specific heat for vaporization of water (= 2 256 kJ/kg), in joules per kilogram (J/kg);
ISO/DIS 14505-2:2025(en)
R is the thermal resistance of the clothing combination, in square metres degree Celsius per watt
clo
[(m °C)/W];
R is the thermal resistance of the seat or the contacting surface, in square metres degree Celsius per
seat
watt [(m °C)/W];
t is the ambient temperature, in degrees Celsius (°C);
env
t is the local skin temperature, in degrees Celsius (°C);
skin
t is the contact area temperature in the real environment, in degrees Celsius (°C);
nod
x is the specific humidity of the surrounding air, in kilograms per kilogram (kg/kg);
env
x is the specific humidity at contact area, in kilograms per kilogram (kg/kg);
nod
is the electrical efficiency of the seat heating (-).
η

If m = 0 , evaporative heat (e.g. sweating and insensible perspiration) is ignored.
da
Replacing the single terms in (17) by equations (18) – (23) and rearranging the terms, finally leads to (24),
which holds the mathematical model for the calculation of t .
nod
mx ⋅ −xc⋅
()
 
1 da nodenv P,vap
+ ⋅t
 
skin
R A
clo cont
 
t =
nod
mc ⋅⋅+xc
()
1 1 da P,da nodP,vap
+ +
R RR A
clo seat cont
(24)
  
mc⋅ +x ⋅c
()
da P,da envvP,vap
 + ⋅tq+
envheat
 
R A
seat cont
 
+

mc⋅ ++xc⋅
()
1 1 da P,da nodP,vap
+ +
RR A
closeat cont
Since the equivalent heat flux depends on the heat fluxes in the real thermal environment, as described in
Figure 1, it can be calculated by application of the heat fluxes on the environmental-side or skin-surface-
side of the balance with equations (25) or (26), respectively. R is a fixed, calibrated insulation value
calib
corresponding to a generally defined virtual clothing insulation.
tt=−Rq⋅+qq−−q (25)
()
eq ,,cont skin calibseatair outair ,in heat
tt=−Rq⋅+q (26)
()
eq ,cont skin calibclo evp
where R is the virtual thermal resistance between t and t , in square metres Kelvin per watt
calib eq,cont skin
[(m °C)/W].
As mentioned in the introduction to this chapter, x should be measured by experiments with participants,
nod
but it can also be estimated using a theoretical sweating model instead of a thermal manikin. As a result, it
can also be used to evaluate air conditioning seats of a blow-out type, which are difficult to measure with.

ISO/DIS 14505-2:2025(en)
Annex A
(informative)
Examples of measuring instruments
A.1 Thermal manikins
A thermal manikin comprises a human-sized and -shaped sensor with its surface covered with numerous,
individually controlled, heated zones. It is suitable for measurement of whole body as well as local t . The
eq
independent zones of the manikin are heated to a controlled and measured temperature. Low-voltage
power is pulsed to each zone at a rate that allows the maintenance of a chosen constant or variable surface
temperature. It is also possible to maintain a constant power supply to the surface.
The power consumption under steady-state conditions is a measure of the convective, radiative and
conductive heat losses (dry heat loss). Measurements and regulation are made with a computer system.
Typically, the quantity measured for each zone is the power consumption or heat loss, Q (W/m ), and the
surface temperature, t (°C). The direct measurement of Q and t eliminates the need for determining the
s s
other components. By normalization to a climate according to the definition of equivalent temperature, the
heat loss can be converted to an equivalent temperature. The technical data of two manikins are presented
in Figure A.1 and Table A.1. More details of the measurement and regulation system can be found in the
Bibliography.
Manikin 1 Manikin 2
33 zones 16 zones
Figure A.1 — Schematic pictures of two heated manikins and their division into different zones

ISO/DIS 14505-2:2025(en)
Table A.1 — Technical data for the two examples of thermal manikins
Manikin Male Female
Clothing size C50 –
Length Sitting (fixed position) 166 cm
Weight 16 kg 31 kg
Number of zones 33 + 3 t 16
a
Regulation principle (see Annex B) Constant t Constant t
sk sk
Constant Q Constant Q
Comfort equation Comfort equation
Clothing 0,6 clo Nude + 0,51 clo
A.2 Discrete, heat integrating sensors
A.2.1 Flat, heated sensors
Flat, heated sensor elements of various design and shape can be used for determination of directional t .
eq
One type of sensor is made of a heated, single element. It consists of a small flat platinum surface, which is
electricall
...

FINAL DRAFT
International
Standard
ISO/TC 159/SC 5
Ergonomics of the thermal
Secretariat: BSI
environment — Evaluation of
Voting begins on:
thermal environments in vehicles —
2026-04-24
Part 2:
Voting terminates on:
2026-06-19
Determination of equivalent
temperature
Ergonomie des ambiances thermiques — Évaluation des
ambiances thermiques dans les véhicules —
Partie 2: Détermination de la température équivalente
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
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INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 159/SC 5
Ergonomics of the thermal
Secretariat: BSI
environment — Evaluation of
Voting begins on:
thermal environments in vehicles —
Part 2:
Voting terminates on:
Determination of equivalent
temperature
Ergonomie des ambiances thermiques — Évaluation des
ambiances thermiques dans les véhicules —
Partie 2: Détermination de la température équivalente
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/CEN PARALLEL PROCESSING
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
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TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
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Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Assessment principles . 2
4.1 General .2
4.2 General description of equivalent temperature .3
4.3 General determination principle of equivalent temperature .3
5 Specific equivalent temperatures . 4
5.1 General .4
5.2 Whole body equivalent temperature . .4
5.2.1 Determination principle .4
5.2.2 Calculation .4
5.3 Segmental equivalent temperature .5
5.3.1 Determination principle .5
5.3.2 Calculation .5
5.4 Directional equivalent temperature .5
5.4.1 Determination principle .5
5.4.2 Calculation .6
5.5 Omnidirectional equivalent temperature .6
5.5.1 Determination principle .6
5.5.2 Calculation .7
6 Measuring instruments . 7
7 Assessment . . 8
7.1 General .8
7.2 Determination of whole body equivalent temperature .8
7.2.1 General .8
7.2.2 Determination with omnidirectional sensors .8
7.2.3 Determination with a thermal manikin .8
7.3 Determination of local equivalent temperature .8
7.3.1 General .8
7.3.2 Determination with omnidirectional sensors or flat, heated sensors .8
7.3.3 Determination with a thermal manikin .9
8 Equivalent contact temperature . 9
8.1 General .9
8.2 Calculation methodology.9
Annex A (informative) Examples of measuring instruments. 14
Annex B (informative) Characteristics and specifications of measuring instruments . 17
Annex C (informative) Calibration and other determinations .22
Annex D (informative) Interpretation of equivalent temperature .24
Annex E (informative) Examples .28
Bibliography .32

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 159, Ergonomics, Subcommittee SC 5,
Ergonomics of the physical environment, in collaboration with the European Committee for Standardization
(CEN) Technical Committee CEN/TC 122, Ergonomics, in accordance with the Agreement on technical
cooperation between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 14505-2:2006/Cor 1:2007), which has been
technically revised.
The main change is as follows:
— addition of an evaluation method for the contact areas (equivalent contact temperature).
A list of all parts in the ISO 14505 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
The interaction of convective, radiative and conductive heat exchange in a vehicle compartment is very
complex. External thermal loads in combination with the internal heating and ventilation system of the
vehicle create a local climate that can vary considerably in space and time. Asymmetric thermal conditions
arise, and these are often the main cause of complaints of thermal discomfort. In vehicles without or with
poor heating, ventilating and air-conditioning system (HVAC-system), thermal stress is determined largely
by the impact of the ambient climatic conditions on the vehicle compartment.
Subjective evaluation is integrative, as the individual combines into one reaction the combined effect
of several thermal stimuli. However, it is not sufficiently detailed or accurate for repeated use. Technical
measurements provide detailed and accurate information but must be integrated in order to predict the
thermal effects on humans. Since several climatic factors play a role for the final heat exchange of a person,
these factors must be integrated to a measure, representing their relative importance.
This document includes the equivalent temperature models t for the assessment of the thermal conditions.
eq
For special consideration of the seat, the equivalent contact temperature t can be applied for body
eq,cont
compartments in contact to surfaces. Methods for the calculation of t using thermal factors are described
eq
in ISO 14505-4. The methodology described in this document can also be used in specific performance
standards for testing of HVAC-systems for vehicles and similar confined spaces.

v
FINAL DRAFT International Standard ISO/FDIS 14505-2:2026(en)
Ergonomics of the thermal environment — Evaluation of
thermal environments in vehicles —
Part 2:
Determination of equivalent temperature
1 Scope
This document specifies requirements and recommendations for the assessment of the thermal conditions
inside a vehicle compartment. It can also be applied to other confined spaces with asymmetric climatic
conditions.
It applies to the assessment of thermal conditions, when deviations from thermal neutrality are relatively
small.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 13731, Ergonomics of the thermal environment — Vocabulary and symbols
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13731 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
equivalent temperature
t
eq
temperature of a standard homogenous space, in which a person exchanges the same heat loss by convection
and radiation as in the actual conditions under assessment
Note 1 to entry: The standard homogenous space is defined as an environment in which the mean radiant temperature
is equal to the air temperature and there is zero air velocity.
3.2
whole body equivalent temperature
t
eq,whole
temperature of an imaginary enclosure with the same temperature in air and on surrounding surfaces and
with air velocity equal to zero in which a full-scale, human shaped, heated sensor will exchange the same
dry heat by radiation and convection as in the actual non-uniform environment

3.3
segmental equivalent temperature
t
eq,segment
uniform temperature of an imaginary enclosure with the same temperature in air and on surrounding
surfaces and with air velocity equal to zero in which one or more selected zones of a thermal manikin will
exchange the same dry heat by radiation and convection as in the actual non-uniform environment
3.4
directional equivalent temperature
t
eq,direct
uniform temperature of an imaginary enclosure with the same temperature in air and on surrounding
surfaces and with air velocity equal to zero in which a small flat heated surface will exchange the same dry
heat by radiation and convection as in the actual non-uniform environment
3.5
omnidirectional equivalent temperature
t
eq,omni
uniform temperature of an imaginary enclosure with the same temperature in air and on surrounding
surfaces and with air velocity equal to zero in which a heated ellipsoid will exchange the same dry heat by
radiation and convection as in the actual non-uniform environment
3.6
equivalent contact temperature
t
eq,cont
uniform temperature of an imaginary contact surface in a standard homogeneous space, at which a person
will exchange the same amount of dry heat through thermal conduction for a virtual clothing insulation as
in the actual non-uniform environment
Note 1 to entry: The standard homogenous space is defined as an environment in which the mean radiant temperature
is equal to the air temperature and there is zero air velocity. In the actual non-uniform environment, the person
experiences sensible and latent heat transfer at the considered body parts.
3.7
segment
part of a human-shaped sensor, normally corresponding to a real body-part, consisting of one or several
whole zones, for which a segmental equivalent temperature, t , is presented
eq,segment
3.8
zone
physical partition of a manikin, which is independently regulated and within which the surface temperature
and heat exchange is measured
3.9
heating, ventilating and air-conditioning system
HVAC-system
devices that control the temperature, humidity, and purity of the air in an enclosed space
4 Assessment principles
4.1 General
The assessment principle is based on the measurement of the equivalent temperature. The equivalent
temperature provides a unified, physical measure of the climatic effects on the human dry heat exchange.
On the basis of the actual value for, and the variation in, equivalent temperature, it is possible to predict
the conditions for heat balance under conditions in or close to the thermoneutral zone. People’s thermal
sensation is primarily influenced by general and local levels and variations in skin surface heat flux. Values
for the equivalent temperature of a specified environment have been found to be closely related to how
[12]
people perceive thermal conditions when exposed to the same environment. This can be used for the
interpretation of the t value and assessment of the quality of the environment.
eq
The climate is assessed in terms of a total equivalent temperature, which describes the level of thermal
neutrality.
The climate is also assessed for local effects on specified parts of the human body surface. The local
equivalent temperatures determine to what extent the actual body parts fall within the range of acceptable
levels of heat loss (local discomfort).
4.2 General description of equivalent temperature
The equivalent temperature is a pure physical quantity, that in a physically sound way integrates the
independent effects of convection and radiation on human body heat exchange. This relationship is best
described for the overall (whole body) heat exchange. There is limited experience with relations between
local dry heat exchange and local equivalent temperature. The standardized definition of t applies only
eq
for the whole body. Therefore, the definition is modified for the purposes of this document. t does not take
eq
into account human perception and sensation or other subjective aspects. However, empirical studies show
that t values are well related to the subjective perception of the thermal effect.
eq
4.3 General determination principle of equivalent temperature
Determination of t is based on Formula (1) and (2) for convective and radiative heat transfer for clothed
eq
persons. Heat exchange by conduction is assumed to be small and accounted for by radiation and convection.
Rh=× tt (1)

rskr
Ch=× tt (2)

cska
where
R is heat exchange by radiation, in watts per square metre (W/m );
C is heat exchange by convection, in watts per square metre (W/m );
h is the radiation heat transfer coefficient, in watts per square metre Kelvin [W/(m K)];
r
h is the convection heat transfer coefficient, in watts per square metre Kelvin [W/(m K)];
c
t is the skin temperature, in degrees Celsius (°C);
sk
t is the mean radiant temperature, in degrees Celsius (°C);
r
t is the ambient air temperature, in degrees Celsius (°C).
a
In practice, the equivalent temperature is determined according to Formula (3) based on the measured
convective and radiative heat losses (Formula (4)):
Q
tt= − (3)
eq s
h
cal
QR=+C (4)
where
t is the surface temperature, in degrees Celsius (°C);
s
t is the temperature of the standard environment, in degrees Celsius (°C);
eq
Q is the measured convective and radiative heat loss during the actual conditions, in watts per
square metre (W/m );
h is the combined heat transfer coefficient, determined during calibration in a standard
cal
environment, in watts per square metre Kelvin [W/(m K)].
The standard environment comprises homogenous, uniform thermal conditions with t = t and air velocity
a
r
v , < 0,1 m/s. A suitable calibration procedure is described in the informative Annex C.
a
5 Specific equivalent temperatures
5.1 General
As there is no method available for measurement of the true total or local t , four specific equivalent
eq
temperatures are calculated according to different principles, according to 5.2 to 5.5. Depending on the
measuring principles, the following are specified, which are further described in Reference [13]:
a) whole body equivalent temperature;
b) segmental equivalent temperature;
c) directional equivalent temperature;
d) omnidirectional equivalent temperature.
5.2 Whole body equivalent temperature
5.2.1 Determination principle
The principle of determination is to measure the total heat flow from a human-sized test manikin consisting
of several zones, each with a specific measured surface temperature similar to that of a human being.
Theoretically, whole body equivalent temperature can be measured with thermal manikins or a large
number of flat heated sensors attached to an unheated manikin. The accuracy of the result is depending
on surface temperature, size of body, number and division of zones, posture etc. An appropriate method
to use is a thermal manikin divided into separate, individually heated zones covering the whole body, with
surface temperatures close to that of a real human being. A human-sized manikin with only one zone will
not determine a realistic whole body t because the thermal conditions vary too much over the surface. The
eq
more zones the manikin has, the more correct value it will measure.
5.2.2 Calculation
The calculation of the whole body equivalent temperature is based on the Formula (5) depending on the
whole body skin temperature, determined by Formula (6), and whole body heat loss, determined by
Formula (7).
Q
whole
tt= − (5)
eq,whole sk,whole
h
cal,whole
tA


sk,n n
t = (6)
sk,whole
A

n
QA


nn
Q = (7)
whole
A

n
where
A is a weighting factor based on the surface area;
h is determined by calibration in a standard environment (see informative Annex C);
cal,whole
n is the number of zones of the body (0 < n ≤ N).
In order to be able to compare results from other manikins, the measured t should be presented together
eq
with specifications of the manikin used, such as regulation principle, skin temperature, number of zones etc.
(see informative Annexes A and B).

5.3 Segmental equivalent temperature
5.3.1 Determination principle
The principle of determination is to measure the total heat flow from a segment consisting of one or more
zones, each with a specific measured surface temperature similar to that of a human being.
The segmental t is based on the heat flow from a certain part of the body, i.e. a segment, such as hand,
eq
head or chest. The segmental t can only be measured with a full-sized, human-shaped heated sensor,
eq
e.g. a thermal manikin. The number of zones and the partition between them shall at least be such that it
corresponds to the actual segment that the segmental t should be measured for. Some segments, e.g. thigh,
eq
shall be divided into at least two zones within the segment, because the thermal conditions are different on
the front and the rear (seat contact) side in the case of the thigh.
5.3.2 Calculation
The calculation of the segmental equivalent temperature is based on the Formula (8) depending on
the segmental skin temperature, determined by Formula (9), and segmental heat loss, determined by
Formula (10).
Q
segment
tt= − (8)
eq,segment sk,segment
h
cal,segment
tA


sk,n n
t = (9)
sk,segment
A

n
QA


nn
Q = (10)
segment
A

n
where
h is determined by calibration in a standard environment (see informative Annex C);
cal,segment
N is the number of zones of the body (0 < n ≤ N).
The segment can be freely chosen, but it shall consist of one or more whole zones. Normally, body parts
like head, hands, arms, feet, legs, chest, back and seat are chosen. To be able to compare results from other
measurements, the measured t should be presented with specifications about the segment used, such
eq
as regulation principle, surface temperature, which body part, number, size and partition of zones of the
segment (see informative Annexes A and B).
5.4 Directional equivalent temperature
5.4.1 Determination principle
The principle of determination is to measure the total heat flow from a small flat surface with a measured
surface temperature. The directional t can be described as a normal vector to the measuring plane in every
eq
point, defined by magnitude and direction. It refers to the heat exchange within the half-sphere in front of
the infinitesimal plane. The directional t can only be measured with a flat sensor, which can be attached to
eq
an unheated manikin or other positioning device. Several sensors can be used simultaneously to determine
directional t at other locations or in other directions, provided that they are positioned so that they do not
eq
influence each other.
5.4.2 Calculation
The calculation of the directional equivalent temperature is based on the Formula (11) depending on the
heat flow from the sensor.
Q
direct
tt= − (11)
eq,directsk,direct
h
cal,direct
where
t is the surface temperature of the sensor;
sk,direct
Q is the heat flow from the sensor;
direct
h is determined by calibration of the sensor in a standard environment (see informative Annex C).
cal,direct
A local equivalent temperature, t , can be calculated as an average value from several measurements
eq,local
at the same location but in different directions. It can be calculated as an arithmetic mean value without
weighting factors as shown in Formula (12) or with weighting as shown in Formula (13) to simulate a certain
body posture.
t
∑
eq,direct,n
t = (12)
eq,local
n
where n is the number of directions.
tt= A (13)


eq,local eq,direct,nn
where n is the number of measurements, with Σ(A ) = 1, and A represents body postures.
n
A total equivalent temperature can be calculated as a weighted mean value of local equivalent temperatures
as shown in Formula (14).
tt= A (14)


eq,total eq,local,nn
where n is the number of locations, with Σ(A ) = 1.
n
In order to be able to compare results from other measurements, the measured t should be presented
eq
with specifications about the sensor used, such as regulation principle, surface temperature, size and also
location and direction of the sensor (see informative Annexes A and B). Whole body t and total t is not
eq eq
the same. In an asymmetric climate and with seat contact, the difference between them will be considerable.
5.5 Omnidirectional equivalent temperature
5.5.1 Determination principle
The principle of determination is to measure the total heat flow from the surface of an ellipsoid with a
measured surface temperature. The omnidirectional t can be described as the weighted mean value of
eq
the directional t in all directions. The weighting factors for the different directions are dependent of the
eq
form of the ellipsoid. It refers to the heat exchange in all directions. The omnidirectional t can only be
eq
measured with an ellipsoid sensor with uniform heat flow over the surface. One or more sensors can be used
simultaneously. If more than one sensor is used, it shall be pointed out that the sensors will influence each
other as hot surfaces in the sphere that is measured.

5.5.2 Calculation
The calculation of the omnidirectional equivalent temperature is based on the Formula (15) depending on
the heat flow from the sensor.
Q
omni
tt= − (15)
eq,omnisk,omni
h
cal,omni
where
t is the surface temperature of the sensor;
sk,omni
Q is the heat flow from the sensor;
omni
h is determined by calibration of the sensor in a standard environment (see informative Annex C).
cal,omni
Omnidirectional t determined with one ellipsoid sensor in an asymmetric climate is a local t . A total t
eq eq eq
can be calculated as an arithmetic mean value from sensors at different locations with weighting factors for
different body parts according to SAE-J-2234 as shown in Formula (16).
tt=A (16)

eq,total eq,loca,ln n
where n is the number of locations, with Σ(A ) = 1.
n
In order to be able to compare results from other measurements, the measured t should be presented
eq
with specifications about the sensor used, such as regulation principle, surface temperature, size and also
location and direction of the sensor (see informative Annexes A and B).
6 Measuring instruments
Several measurement methods and instruments, representing different measuring principles, are given in
informative Annexes A and B. Depending on needs, a method given in informative Annex A can be selected.
Measurement values obtained with principally different methods are not comparable with each other. They
represent different levels in terms of:
— reliability;
— relevance;
— validity;
— repeatability;
— accuracy;
— integration;
— complexity;
— cost;
— availability.
Performance and requirements of the specific methods are given in informative Annex B. Requirements for
calibration procedures are given in informative Annex C.

7 Assessment
7.1 General
The equivalent temperature represents a quantitative assessment of the conditions for physical heat
exchange. The numeric value of t is a temperature level that can come close to “normal” expected room
eq
temperatures. Higher t values indicate lower heat losses (“warmer”), while lower t values indicate higher
eq eq
heat losses (“colder”).
The interpretation of equivalent temperature in terms of anticipated perceived thermal sensation is based
on series of experiments with participants in which the different types of equivalent temperature have
been measured. Examples of interpretation are given in informative Annex C. For some types of equivalent
temperature, data are not available for comparison with human responses. Nevertheless, these kinds of
measurement can be used for differential measurements of thermal conditions. Application examples for t
eq
are given in informative Annex E.
7.2 Determination of whole body equivalent temperature
7.2.1 General
Determination of whole body equivalent temperature should preferably be done with measurements using
a thermal manikin or by integration of discrete measurements using omnidirectional sensors placed at
specified positions in the vehicle cabin.
7.2.2 Determination with omnidirectional sensors
Omnidirectional sensors are described in informative Annexes A and B. Sensors are placed on a stand
simulating a person and placed in a seat of the vehicle. At least six sensors are placed in relevant positions and
measurements are made when steady state is achieved. Whole body equivalent temperature is determined
as the area-weighted average of the individual sensors. Interpretation of values should be made according to
informative Annex D.
7.2.3 Determination with a thermal manikin
Requirements for the manikin and procedures are described in informative Annexes A and B. The manikin
is placed in a seat in the vehicle and whole-body heat loss is measured when steady state conditions are
achieved. Whole body heat loss is the area-weighted average of the independent segments of the manikin.
Interpretation of values should be made according to informative Annex D.
7.3 Determination of local equivalent temperature
7.3.1 General
Determination of whole body equivalent temperature should preferably be done with measurements using a
thermal manikin or by the integration of discrete measurements using omnidirectional sensors.
7.3.2 Determination with omnidirectional sensors or flat, heated sensors
Omnidirectional sensors are described in informative Annex A. Sensors are placed on a stand simulating
a person and placed in a seat of the vehicle or at specified spots on the surface of the clothing of a person
or a manikin. Measurements are made when steady state is achieved. Local equivalent temperature is
determined as the value of the individual sensor. The more sensors located in the space, the better resolution
of the variation in the thermal field around the human body.

7.3.3 Determination with a thermal manikin
Requirements for the manikin and procedures are described in informative Annexes A and B. The manikin
is placed in a seat in the vehicle and heat loss is measured from a local segment of the manikin when steady
state conditions are achieved. Local equivalent temperature is determined by the measured value of the
individual segment and represent that particular segment only. Interpretation of values should be made
according to informative Annex D.
8 Equivalent contact temperature
8.1 General
The heat exchange between a person and a contacting surface by heat conduction as well as moisture is not
negligible and has a significant influence on the thermal sensation. An example of the compensation effect
of seat heating is given in informative Annex E. The calculation of the equivalent contact temperature t
eq,cont
is based on the equations for heat conduction as well as latent and sensible heat exchange between a clothed
person and the contacting surfaces.
As shown in Figure 1, the principles for specification of the equivalent contact temperature t and
eq,cont
equivalent temperature t are similar to each other and both depend on the air velocity v in the real
eq air
environment. In the equivalent temperature model, the equivalent heat flux q depends on the convective
eq
q and radiant heat fluxes q in the real environment with the determined radiant temperature t , air
conv rad r
temperature t and skin temperature t . The equivalent contact temperature t includes the detailed
air skin eq,cont
description of the thermodynamic situation at the contact interface between a seat and the human body
surface. Here, the equivalent heat flux q depends on the combined effect of heat conduction through
eq,cont
the clothing q and the seat q as well as the change in enthalpy due to sensible and latent heat transfer
clo seat
in the real environment, such as by the moisture flow from skin to contact area q . These mechanisms can
evp
be influenced by the use of mechanically induced air flow rates (e.g. seat ventilation, q - q ) or heat
air,out air,in
sources (e.g. seat heating, q ).
heat
This clause describes an index for evaluating the thermal comfort of seats. A measure for the palm area
can be derived on the base of the contact temperature defined in ISO/TS 13732-2. This t evaluation
eq,cont
method is basically based on experiments with participants, but it can also be applied to evaluations using
thermal manikins, as described in Clause 7, by replacing the evaporation effects of perspiration on the seat
contact surface with a theoretical model. This means a suitable theoretical sweating model is available for
evaluating t with a thermal manikin instead of a participant.
eq,cont
8.2 Calculation methodology
As can be seen from Figure 1, the calculation of t is based on the balance of heat flux densities at an
eq,cont
infinitesimal volume element (green area). The equivalent heat flux q [see Figure 1 b), right-hand
eq,cont
side] depends on the heat fluxes in the real environment [see Figure 1 b), left-hand side] according to the
equations in the centre of Figure 1 b). The volume element is represented by node K at which the energy
balance is performed. Furthermore, K represents the contact interface between the human body and any
kind of contacting surface.
a)
b)
NOTE The t is described using a nodal energy balance at node K (left-hand side: heat fluxes in real
eq,cont
environment, right-hand side: heat flux in equivalent environment with a calibrated insulation value R ).
calib
Figure 1 — Specification and physical interpretation of the equivalent temperature: a) and
equivalent contact temperature b).

The energy balance at node K is described by Formula (17), where negative quantities leave K and positive
ones enter K.
q+qq−−+q q+q=0 (17)
cloevp seat air,in air,outheat
where
q is the heat flux density through the clothing, in watts per square metre (W/m );
clo
q is the heat flux density of the moisture flow through the clothing, in watts per square metre
evp
(W/m );
q is the heat flux density through the seat, in watts per square metre (W/m );
seat
q is the heat flux density of the incoming mass air flow by seat fan, in watts per square metre (W/
air,in
m );
q is the heat flux density of the outgoing mass air flow by seat fan, in watts per square metre (W/
air,out
m );
q is the heat flux density of an optional internal heat source, in watts per square metre (W/m ).
heat
Formulae 18 to 23 describe a simplified three-node model (Figure 1) for seat integration. The air mass flow is
assumed to be 100 % efficient, with no short-circuit to ambient air. The incoming air temperature is assumed
equal to the ambient air temperature, and the outgoing air temperature is assumed equal to the contact
area temperature. These formulae are of theoretical character and are intended to illustrate the approach.
Manufacturer-dependent parameters, such as contact areas and electrical efficiencies, are not specified. The
heat flux densities in the real environment, visualized on the left-hand side of Figure 1b are subsequently
described with the heat flux density through the clothing layer q (Formula (18)), the evaporative heat flux
clo
density between skin and contact area q (Formula (19)), the conductive heat flux density through the seat
evp
q (Formula (20)), the outgoing heat flux density due to the seat ventilation q (Formula (21)) as well
seat air,out
as the incoming heat flux density due to the seat ventilation q (Formula (22)) and the heat flux generated
air,in
by the use of a heat source q (Formula (23)).
heat
tt−
skin nod
q= (18)
clo
R
clo

mr+ct  xx


da 0 P,vapskinnod env
q= (19)
evp
A
cont
tt−
nodenv
q= (20)
seat
R
seat

mc×+tx (r +ct )

da P,da nodnod 0P,vap nod
q= (21)
air,out
A
cont

mctx+(rc+)t

da P,da envenv 0P,vap env
q= (22)
air,in
A
cont
A Q
cont el
q=  (23)
heat
A A
tot tot
where
A is the contacting surface area related to a person’s body, in square metres (m );
cont
A is the total heated seat surface area, in square metres (m );
tot
c is the specific heat capacity of water vapor (= 2 080 J/(kg K)), in joules per kilogram Kelvin [J/
p,vap
(kg K)];
c is the specific heat capacity of dry air (= 1 005 J/(kg K)), in joules per kilogram Kelvin [J/
p,da
(kg K)];

m is the mass flow rate generated by the seat fans, in kilograms per second (kg/s);
da
Q is the electrical power consumed by the seat heating, in watts (W);
el
r is the specific heat for vaporization of water (= 2 256 kJ/kg), in joules per kilogram (J/kg);
R is the thermal resistance of the clothing combination, in square metres Kelvin per watt
clo
[(m K)/W];
R is the thermal resistance of the seat or the contacting surface, in square metres Kelvin per watt
seat
[(m K)/W];
t is the ambient temperature, in degrees Celsius (°C);
env
t is the local skin temperature, in degrees Celsius (°C);
skin
t is the contact area temperature in the real environment, in degrees Celsius (°C);
nod
x is the specific humidity of the surrounding air, in kilograms per kilogram (kg/kg);
env
x is the specific humidity at contact area, in kilograms per kilogram (kg/kg);
nod
is the electrical efficiency of the seat heating (-).
η

If m = 0 , evaporative heat (e.g. sweating and insensible perspiration) is ignored.
da
Replacing the single terms in Formula (17) by Formula (18) to Formula (23) and rearranging the terms,
finally leads to Formula (24), whic
...

ISO/DISFDIS 14505-2:2025(en)
ISO /TC 159/SC 5
Secretariat: BSI
Date: 2025-07-072026-04-10
Ergonomics of the thermal environment — Evaluation of thermal
environments in vehicles —
Part 2:
Determination of equivalent temperature
Ergonomie des ambiances thermiques — Évaluation des ambiances thermiques dans les véhicules —
Partie 2: Détermination de la température équivalente
FDIS stage
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All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this
publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical,
including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can
be requested from either ISO at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
EmailE-mail: [e-mail]
Website: www.iso.org
Published in Switzerland
ISO/DIS 14505-2:2025(en)
Contents
Foreword .iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Assessment principles . 2
4.1 General . 2
4.2 General description of equivalent temperature . 3
4.3 General determination principle of equivalent temperature . 3
5 Specific equivalent temperatures . 4
5.1 General . 4
5.2 Whole body equivalent temperature . 4
5.3 Segmental equivalent temperature . 5
5.4 Directional equivalent temperature . 6
5.5 Omnidirectional equivalent temperature . 7
6 Measuring instruments . 7
7 Assessment . 8
7.1 General . 8
7.2 Determination of whole body equivalent temperature. 8
7.3 Determination of local equivalent temperature . 9
8 Equivalent contact temperature . 9
8.1 General . 9
8.2 Calculation methodology . 10
Annex A (informative) Examples of measuring instruments . 14
Annex B (informative) Characteristics and specifications of measuring instruments . 18
Annex C (informative) Calibration and other determinations . 24
Annex D (informative) Interpretation of equivalent temperature . 26
Annex E (informative) Examples . 32
Bibliography . 37

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO
collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of
(a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO had not received notice
of (a) patent(s) which may be required to implement this document. However, implementers are
cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all
such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the World
Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 159, Ergonomics, Subcommittee SC 5,
Ergonomics of the physical environment, in collaboration with the European Committee for
Standardization (CEN) Technical Committee CEN/TC 122, Ergonomics, in accordance with the Agreement
on technical cooperation between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 14505-2:2006/Cor 1:2007), which has
been technically revised.
The main change is as follows:
— — addition of an evaluation method for the contact areas (equivalent contact temperature) has been
added.).
A list of all parts in the ISO 14505 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
ISO/DIS 14505-2:2025(en)
Introduction
The interaction of convective, radiative and conductive heat exchange in a vehicle compartment is very
complex. External thermal loads in combination with the internal heating and ventilation system of the
vehicle create a local climate that can vary considerably in space and time. Asymmetric thermal
conditions arise, and these are often the main cause of complaints of thermal discomfort. In vehicles
without or with poor heating, ventilating and air-conditioning system (HVAC-system), thermal stress is
determined largely by the impact of the ambient climatic conditions on the vehicle compartment.
Subjective evaluation is integrative, as the individual combines into one reaction the combined effect of
several thermal stimuli. However, it is not sufficiently detailed or accurate for repeated use. Technical
measurements provide detailed and accurate information but must be integrated in order to predict the
thermal effects on humans. Since several climatic factors play a role for the final heat exchange of a
person, these factors must be integrated to a measure, representing their relative importance.
This document includes the equivalent temperature models t for the assessment of the thermal
eq
conditions. For special consideration of the seat, the equivalent contact temperature t can be applied
eq,cont
for body compartments in contact to surfaces. Methods for the calculation of t using thermal factors are
eq
described in ISO 14505-4. The methodology described in this document can also be used in specific
performance standards for testing of HVAC-systems for vehicles and similar confined spaces.
v
vi
DRAFT International Standard ISO/DIS 14505-2:2025(en)

Ergonomics of the thermal environment — Evaluation of thermal
environments in vehicles —
Part 2:
Determination of equivalent temperature
1 Scope
This document gives guidelinesspecifies requirements and recommendations for the assessment of the
thermal conditions inside a vehicle compartment. It can also be applied to other confined spaces with
asymmetric climatic conditions.
It applies forto the assessment of thermal conditions, when deviations from thermal neutrality are relatively
small.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 13731, Ergonomics of the thermal environment — Vocabulary and symbols
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13731 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/
3.1 3.1
equivalent temperature
t
eq
temperature of a standard homogenous space, in which a person exchanges the same heat loss by convection
and radiation as in the actual conditions under assessment
NOTE Note 1 to entry: The standard homogenous space is defined as an environment in which the mean radiant
temperature is equal to the air temperature and there is zero air velocity.
3.2 3.2
whole body equivalent temperature
t
eq,whole
temperature of an imaginary enclosure with the same temperature in air and on surrounding surfaces and
with air velocity equal to zero in which a full-scale, human shaped, heated sensor will exchange the same dry
heat by radiation and convection as in the actual non-uniform environment
3.3 3.3
segmental equivalent temperature
t
eq,segment
uniform temperature of an imaginary enclosure with the same temperature in air and on surrounding surfaces
and with air velocity equal to zero in which one or more selected zones of a thermal manikin will exchange
the same dry heat by radiation and convection as in the actual non-uniform environment
3.4 3.4
directional equivalent temperature
t
eq,direct
uniform temperature of an imaginary enclosure with the same temperature in air and on surrounding surfaces
and with air velocity equal to zero in which a small flat heated surface will exchange the same dry heat by
radiation and convection as in the actual non-uniform environment
3.5 3.5
omnidirectional equivalent temperature
t
eq,omni
uniform temperature of an imaginary enclosure with the same temperature in air and on surrounding surfaces
and with air velocity equal to zero in which a heated ellipsoid will exchange the same dry heat by radiation
and convection as in the actual non-uniform environment
3.6 3.6
equivalent contact temperature
t
eq,cont
uniform temperature of an imaginary contact surface in a standard homogeneous space, at which a person
will exchange the same amount of dry heat through thermal conduction for a virtual clothing insulation as in
the actual non-uniform environment
NOTE Note 1 to entry: The standard homogenous space is defined as an environment in which the mean radiant
temperature is equal to the air temperature and there is zero air velocity. In the actual non-uniform environment, the
person experiences sensible and latent heat transfer at the considered body parts.
3.7 3.7
segment
part of a human-shaped sensor, normally corresponding to a real body-part, consisting of one or several whole
zones, for which a segmental equivalent temperature, t , is presented
eq,segment
3.8 3.8
zone
physical partition of a manikin, which is independently regulated and within which the surface temperature
and heat exchange is measured
3.9 3.9
heating, ventilating and air-conditioning system
HVAC-system
devices that control the temperature, humidity, and purity of the air in an enclosed space
4 Assessment principles
4.1 General
The assessment principle is based on the measurement of the equivalent temperature. The equivalent
temperature provides a unified, physical measure of the climatic effects on the human dry heat exchange. On
the basis of the actual value for, and the variation in, equivalent temperature, it is possible to predict the
conditions for heat balance under conditions in or close to the thermoneutral zone. People’s thermal sensation
ISO/DISFDIS 14505-2:20252026(en)
is primarily influenced by general and local levels and variations in skin surface heat flux. Values for the
equivalent temperature of a specified environment have been found to be closely related to how people
[12] [12]
perceive thermal conditions when exposed to the same environment . This can be used for the
interpretation of the t value and assessment of the quality of the environment.
eq
The climate is assessed in terms of a total equivalent temperature, which describes the level of thermal
neutrality.
The climate is also assessed for local effects on specified parts of the human body surface. The local equivalent
temperatures determine to what extent the actual body parts fall within the range of acceptable levels of heat
loss (local discomfort).
4.2 General description of equivalent temperature
The equivalent temperature is a pure physical quantity, that in a physically sound way integrates the
independent effects of convection and radiation on human body heat exchange. This relationship is best
described for the overall (whole body) heat exchange. There is limited experience with relations between local
dry heat exchange and local equivalent temperature. The standardized definition of t applies only for the
eq
whole body. Therefore, the definition is modified for the purposes of this document. t does not take into
eq
account human perception and sensation or other subjective aspects. However, empirical studies show that
t values are well related to the subjective perception of the thermal effect.
eq
4.3 General determination principle of equivalent temperature
Determination of t is based on Formula (1)Formula (1) and (2)(2) for convective and radiative heat transfer
eq
for clothed persons. Heat exchange by conduction is assumed to be small and accounted for by radiation and
convection.
¯
𝑅𝑅 =ℎ ×(𝑡𝑡 −𝑡𝑡 )
𝑟𝑟 𝑠𝑠𝑠𝑠 𝑟𝑟
(1)
𝐶𝐶 =ℎ ×(𝑡𝑡 −𝑡𝑡 ) (2)
𝑐𝑐 𝑠𝑠𝑠𝑠 𝑎𝑎
where
R is heat exchange by radiation, in watts per square metre (W/m );
C is heat exchange by convection, in watts per square metre (W/m );
h is the radiation heat transfer coefficient, in watts per square metre Kelvin [W/(m K)];
r
h is the convection heat transfer coefficient, in watts per square metre Kelvin [W/(m K)];
c
t is the skin temperature, in degrees Celsius (°C);
sk
¯
𝑡𝑡 is the mean radiant temperature, in degrees Celsius (°C);
𝑟𝑟
t is the ambient air temperature, in degrees Celsius (°C).
a
In practice, the equivalent temperature is determined according to Formula (3)Formula (3) based on the
measured convective and radiative heat losses (Formula (4)(Formula (4)):):
𝑄𝑄
𝑡𝑡 =𝑡𝑡 − (3)
𝑒𝑒𝑒𝑒 𝑠𝑠
ℎ
𝑐𝑐𝑐𝑐𝑐𝑐
𝑄𝑄 =𝑅𝑅 +𝐶𝐶 (4)
where
t is the surface temperature, in degrees Celsius (°C);
s
t is the temperature of the standard environment, in degrees Celsius (°C);
eq
Q is the measured convective and radiative heat loss during the actual conditions, in watts per square metre (W/m );
h is the combined heat transfer coefficient, determined during calibration in a standard environment, in watts per
cal
square metre Kelvin [W/(m K)].
¯
The standard environment comprises homogenous, uniform thermal conditions with t = 𝑡𝑡 and air velocity
a
𝑟𝑟
v , < 0,1 m/s. A suitable calibration procedure is described in the informative Annex CAnnex C.
a
5 Specific equivalent temperatures
5.1 General
As there is no method available for measurement of the true total or local t , four specific equivalent
eq
temperatures are calculated according to different principles, according to 5.25.2 to 5.55.5. Depending on the
[13]
measuring principles, the following are specified, which are further described in Reference[13]reference ::
a) a) whole body equivalent temperature;
b) b) segmental equivalent temperature;
c) c) directional equivalent temperature;
d) d) omnidirectional equivalent temperature.
5.2 Whole body equivalent temperature
5.2.1 Determination principle
The principle of determination is to measure the total heat flow from a human-sized test manikin consisting
of several zones, each with a specific measured surface temperature similar to that of a human being.
Theoretically, whole body equivalent temperature can be measured with thermal manikins or a large number
of flat heated sensors attached to an unheated manikin. The accuracy of the result is depending on surface
temperature, size of body, number and division of zones, posture etc. An appropriate method to use is a
thermal manikin divided into separate, individually heated zones covering the whole body, with surface
temperatures close to that of a real human being. A human-sized manikin with only one zone will not
determine a realistic whole body t because the thermal conditions vary too much over the surface. The more
eq
zones the manikin has, the more correct value it will measure.
5.2.2 Calculation
The calculation of the whole body equivalent temperature is based on the Formula (5)Formula (5) depending
on the whole body skin temperature, determined by Formula (6)Formula (6),, and whole body heat loss,
determined by Formula (7)Formula (7).
(5)
(6)
(7)
𝑄𝑄
𝑤𝑤ℎ𝑜𝑜𝑐𝑐𝑜𝑜
𝑡𝑡 =𝑡𝑡 − (5)
𝑒𝑒𝑒𝑒,𝑤𝑤ℎ𝑜𝑜𝑜𝑜𝑒𝑒 𝑠𝑠𝑠𝑠,𝑤𝑤ℎ𝑜𝑜𝑜𝑜𝑒𝑒
ℎ
𝑐𝑐𝑐𝑐𝑐𝑐,𝑤𝑤ℎ𝑜𝑜𝑐𝑐𝑜𝑜
∑(𝑡𝑡 ⋅𝐴𝐴 )
𝑠𝑠𝑠𝑠,𝑛𝑛 𝑛𝑛
𝑡𝑡 = (6)
𝑠𝑠𝑠𝑠,𝑤𝑤ℎ𝑜𝑜𝑜𝑜𝑒𝑒
∑𝐴𝐴
𝑛𝑛
∑(𝑄𝑄 ⋅𝐴𝐴 )
𝑛𝑛 𝑛𝑛
𝑄𝑄 =
𝑤𝑤ℎ𝑜𝑜𝑜𝑜𝑒𝑒
∑𝐴𝐴
𝑛𝑛
(7)
ISO/DISFDIS 14505-2:20252026(en)
where
A is a weighting factor based on the surface area;
h is determined by calibration in a standard environment (see informative Annex C);
cal,whole
n is the number of zones of the body (0 < n ≤ N).
In order to be able to compare results from other manikins, the measured t should be presented together
eq
with specifications of the manikin used, such as regulation principle, skin temperature, number of zones etc.
(see informative Annexes AAnnexes A and BB).).
5.3 Segmental equivalent temperature
5.3.1 Determination principle
The principle of determination is to measure the total heat flow from a segment consisting of one or more
zones, each with a specific measured surface temperature similar to that of a human being.
The segmental t is based on the heat flow from a certain part of the body, i.e. a segment, such as hand, head
eq
or chest. The segmental t can only be measured with a full-sized, human-shaped heated sensor, e.g. a thermal
eq
manikin. The number of zones and the partition between them shall at least be such that it corresponds to the
actual segment that the segmental t should be measured for. Some segments, e.g. thigh, shall be divided into
eq
at least two zones within the segment, because the thermal conditions are different on the front and the rear
(seat contact) side in the case of the thigh.
5.3.2 Calculation
The calculation of the segmental equivalent temperature is based on the Formula (8)Formula (8) depending
on the segmental skin temperature, determined by Formula (9)Formula (9),, and segmental heat loss,
determined by Formula (10)Formula (10).
(8)
(9)
(10)
𝑄𝑄
𝑠𝑠𝑜𝑜𝑠𝑠𝑠𝑠𝑜𝑜𝑛𝑛𝑠𝑠
𝑡𝑡 =𝑡𝑡 − (8)
𝑒𝑒𝑒𝑒,𝑠𝑠𝑒𝑒𝑠𝑠𝑠𝑠𝑒𝑒𝑛𝑛𝑡𝑡 𝑠𝑠𝑠𝑠,𝑠𝑠𝑒𝑒𝑠𝑠𝑠𝑠𝑒𝑒𝑛𝑛𝑡𝑡
ℎ
𝑐𝑐𝑐𝑐𝑐𝑐,𝑠𝑠𝑜𝑜𝑠𝑠𝑠𝑠𝑜𝑜𝑛𝑛𝑠𝑠
∑(𝑡𝑡 ⋅ 𝐴𝐴 )
𝑠𝑠𝑠𝑠,𝑛𝑛 𝑛𝑛
𝑡𝑡 = (9)
𝑠𝑠𝑠𝑠,𝑠𝑠𝑒𝑒𝑠𝑠𝑠𝑠𝑒𝑒𝑛𝑛𝑡𝑡
∑𝐴𝐴
𝑛𝑛
∑(𝑄𝑄 ⋅𝐴𝐴 )
𝑛𝑛 𝑛𝑛
𝑄𝑄 = (10)
𝑠𝑠𝑒𝑒𝑠𝑠𝑠𝑠𝑒𝑒𝑛𝑛𝑡𝑡
∑𝐴𝐴
𝑛𝑛
where
hcal,segment is determined by calibration in a standard environment (see informative Annex C);
N is the number of zones of the body (0 < n ≤ N).
The segment can be freely chosen, but it shall consist of one or more whole zones. Normally, body parts like
head, hands, arms, feet, legs, chest, back and seat are chosen. To be able to compare results from other
measurements, the measured t should be presented with specifications about the segment used, such as
eq
regulation principle, surface temperature, which body part, number, size and partition of zones of the segment
(see informative Annexes AAnnexes A and BB).).
5.4 Directional equivalent temperature
5.4.1 Determination principle
The principle of determination is to measure the total heat flow from a small flat surface with a measured
surface temperature. The directional t can be described as a normal vector to the measuring plane in every
eq
point, defined by magnitude and direction. It refers to the heat exchange within the half-sphere in front of the
infinitesimal plane. The directional t can only be measured with a flat sensor, which can be attached to an
eq
unheated manikin or other positioning device. Several sensors can be used simultaneously to determine
directional t at other locations or in other directions, provided that they are positioned so that they do not
eq
influence each other.
5.4.2 Calculation
The calculation of the directional equivalent temperature is based on the Formula (11)Formula (11)
depending on the heat flow from the sensor.
(11)
𝑄𝑄
𝑑𝑑𝑑𝑑𝑑𝑑𝑜𝑜𝑐𝑐𝑠𝑠
𝑡𝑡 =𝑡𝑡 − (11)
𝑒𝑒𝑒𝑒,𝑑𝑑𝑑𝑑𝑟𝑟𝑒𝑒𝑐𝑐𝑡𝑡 𝑠𝑠𝑠𝑠,𝑑𝑑𝑑𝑑𝑟𝑟𝑒𝑒𝑐𝑐𝑡𝑡
ℎ
𝑐𝑐𝑐𝑐𝑐𝑐,𝑑𝑑𝑑𝑑𝑑𝑑𝑜𝑜𝑐𝑐𝑠𝑠
where
t is the surface temperature of the sensor;
sk,direct
Q is the heat flow from the sensor;
direct
h is determined by calibration of the sensor in a standard environment (see informative Annex C).
cal,direct
A local equivalent temperature, t , can be calculated as an average value from several measurements at
eq,local
the same location but in different directions. It can be calculated as an arithmetic mean value without
weighting factors as shown in Formula (12)Formula (12) or with weighting as shown in Formula (13)Formula
(13) to simulate a certain body posture.
(12)
∑𝑡𝑡
𝑜𝑜𝑒𝑒,𝑑𝑑𝑑𝑑𝑑𝑑𝑜𝑜𝑐𝑐𝑠𝑠,𝑛𝑛
𝑡𝑡 = (12)
𝑒𝑒𝑒𝑒,𝑜𝑜𝑜𝑜𝑐𝑐𝑎𝑎𝑜𝑜
𝑛𝑛
where n is the number of directions.
(13)
𝑡𝑡 =∑(𝑡𝑡 ⋅𝐴𝐴 ) (13)
𝑒𝑒𝑒𝑒,𝑜𝑜𝑜𝑜𝑐𝑐𝑎𝑎𝑜𝑜 𝑒𝑒𝑒𝑒,𝑑𝑑𝑑𝑑𝑟𝑟𝑒𝑒𝑐𝑐𝑡𝑡,𝑛𝑛 𝑛𝑛
where n is the number of measurements, with Σ(A ) = 1, and A represents body postures.
n
A total equivalent temperature can be calculated as a weighted mean value of local equivalent temperatures
as shown in Formula (14)Formula (14).
(14)
𝑡𝑡 =∑(𝑡𝑡 ⋅𝐴𝐴 ) (14)
𝑒𝑒𝑒𝑒,𝑡𝑡𝑜𝑜𝑡𝑡𝑎𝑎𝑜𝑜 𝑒𝑒𝑒𝑒,𝑜𝑜𝑜𝑜𝑐𝑐𝑎𝑎𝑜𝑜,𝑛𝑛 𝑛𝑛
where n is the number of locations, with Σ(A ) = 1.
n
In order to be able to compare results from other measurements, the measured t should be presented with
eq
specifications about the sensor used, such as regulation principle, surface temperature, size and also location
ISO/DISFDIS 14505-2:20252026(en)
and direction of the sensor (see informative Annexes AAnnexes A and BB).). Whole body t and total t is not
eq eq
the same. In an asymmetric climate and with seat contact, the difference between them will be considerable.
5.5 Omnidirectional equivalent temperature
5.5.1 Determination principle
The principle of determination is to measure the total heat flow from the surface of an ellipsoid with a
measured surface temperature. The omnidirectional t can be described as the weighted mean value of the
eq
directional t in all directions. The weighting factors for the different directions are dependent of the form
eq
of the ellipsoid. It refers to the heat exchange in all directions. The omnidirectional t can only be measured
eq
with an ellipsoid sensor with uniform heat flow over the surface. One or more sensors can be used
simultaneously. If more than one sensor is used, it shall be pointed out that the sensors will influence each
other as hot surfaces in the sphere that is measured.
5.5.2 Calculation
The calculation of the omnidirectional equivalent temperature is based on the Formula (15)Formula (15)
depending on the heat flow from the sensor.
(15)
𝑄𝑄
𝑜𝑜𝑠𝑠𝑛𝑛𝑑𝑑
𝑡𝑡 =𝑡𝑡 − (15)
𝑒𝑒𝑒𝑒,𝑜𝑜𝑠𝑠𝑛𝑛𝑑𝑑 𝑠𝑠𝑠𝑠,𝑜𝑜𝑠𝑠𝑛𝑛𝑑𝑑
ℎ
𝑐𝑐𝑐𝑐𝑐𝑐,𝑜𝑜𝑠𝑠𝑛𝑛𝑑𝑑
where
tsk,omni is the surface temperature of the sensor;
Qomni is the heat flow from the sensor;
hcal,omni is determined by calibration of the sensor in a standard environment (see informative Annex C).
Omnidirectional t determined with one ellipsoid sensor in an asymmetric climate is a local t . A total t can
eq eq eq
be calculated as an arithmetic mean value from sensors at different locations with weighting factors for
different body parts according to SAE -J -2234 as shown in Formula (16)Formula (16).
(16)
𝑡𝑡 =𝛴𝛴(𝑡𝑡 ⋅𝐴𝐴 ) (16)
𝑒𝑒𝑒𝑒,𝑡𝑡𝑜𝑜𝑡𝑡𝑎𝑎𝑜𝑜 𝑒𝑒𝑒𝑒,𝑜𝑜𝑜𝑜𝑐𝑐𝑎𝑎𝑜𝑜,𝑛𝑛 𝑛𝑛
where n is the number of locations, with Σ(A ) = 1.
n
In order to be able to compare results from other measurements, the measured t should be presented with
eq
specifications about the sensor used, such as regulation principle, surface temperature, size and also location
and direction of the sensor (see informative Annexes AAnnexes A and BB).).
6 Measuring instruments
Several measurement methods and instruments, representing different measuring principles, are given in
informative Annexes AAnnexes A and BB. Depending on needs, a method as given in informative
Annex AAnnex A should can be selected.
Measurement values obtained with principally different methods are not comparable with each other. They
represent different levels in terms of:
— — reliability;
— — relevance;
— — validity;
— — repeatability;
— — accuracy;
— — integration;
— — complexity;
— — cost;
— — availability.
Performance and requirements of the specific methods are given in informative Annex BAnnex B.
Requirements for calibration procedures are given in informative Annex CAnnex C.
7 Assessment
7.1 General
The equivalent temperature represents a quantitative assessment of the conditions for physical heat
exchange. The numeric value of t is a temperature level that can come close to “normal” expected room
eq
temperatures. Higher t values indicate lower heat losses (“warmer”), while lower t values indicate higher
eq eq
heat losses (“colder”).
The interpretation of equivalent temperature in terms of anticipated perceived thermal sensation is based on
series of experiments with participants in which the different types of equivalent temperature have been
measured. Examples of interpretation are given in informative Annex CAnnex C. For some types of equivalent
temperature, data are not available for comparison with human responses. Nevertheless, these kinds of
measurement can be used for differential measurements of thermal conditions. Application examples for t
eq
are given in informative Annex EAnnex E.
7.2 Determination of whole body equivalent temperature
7.2.1 General
Determination of whole body equivalent temperature should preferably be done with measurements using a
thermal manikin or by integration of discrete measurements using omnidirectional sensors placed at specified
positions in the vehicle cabin.
7.2.2 Determination with omnidirectional sensors
Omnidirectional sensors are described in informative Annexes AAnnexes A and BB. Sensors are placed on a
stand simulating a person and placed in a seat of the vehicle. At least six sensors are placed in relevant
positions and measurements are made when steady state is achieved. Whole body equivalent temperature is
determined as the area-weighted average of the individual sensors. Interpretation of values should be made
according to informative Annex DAnnex D.
7.2.3 Determination with a thermal manikin
Requirements for the manikin and procedures are described in informative Annexes AAnnexes A and BB. The
manikin is placed in a seat in the vehicle and whole -body heat loss is measured when steady state conditions
are achieved. Whole body heat loss is the area-weighted average of the independent segments of the manikin.
Interpretation of values should be made according to informative Annex DAnnex D.
ISO/DISFDIS 14505-2:20252026(en)
7.3 Determination of local equivalent temperature
7.3.1 General
Determination of whole body equivalent temperature should preferably be done with measurements using a
thermal manikin or by the integration of discrete measurements using omnidirectional sensors.
7.3.2 Determination with omnidirectional sensors or flat, heated sensors
Omnidirectional sensors are described in informative Annex AAnnex A. Sensors are placed on a stand
simulating a person and placed in a seat of the vehicle or at specified spots on the surface of the clothing of a
person or a manikin. Measurements are made when steady state is achieved. Local equivalent temperature is
determined as the value of the individual sensor. The more sensors located in the space, the better resolution
of the variation in the thermal field around the human body.
7.3.3 Determination with a thermal manikin
Requirements for the manikin and procedures are described in informative Annexes AAnnexes A and BB. The
manikin is placed in a seat in the vehicle and heat loss is measured from a local segment of the manikin when
steady state conditions are achieved. Local equivalent temperature is determined by the measured value of
the individual segment and represent that particular segment only. Interpretation of values should be made
according to informative Annex DAnnex D.
8 Equivalent contact temperature
8.1 General
The heat exchange between a person and a contacting surface by heat conduction as well as moisture is not
negligible and has a significant influence on the thermal sensation. An example of the compensation effect of
seat heating is given in informative Annex EAnnex E. The calculation of the equivalent contact temperature
t is based on the equations for heat conduction as well as latent and sensible heat exchange between a
eq,cont
clothed person and the contacting surfaces.
As shown in Figure 1Figure 1,, the principles for specification of the equivalent contact temperature t and
eq,cont
equivalent temperature t are similar to each other and both depend on the air velocity v in the real
eq air
environment. In the equivalent temperature model, the equivalent heat flux q depends on the convective
eq
q and radiant heat fluxes q in the real environment with the determined radiant temperature t , air
conv rad r
temperature t and skin temperature t . The equivalent contact temperature t includes the detailed
air skin eq,cont
description of the thermodynamic situation at the contact interface between a seat and the human body
surface. Here, the equivalent heat flux q depends on the combined effect of heat conduction through the
eq,cont
clothing q and the seat q as well as the change in enthalpy due to sensible and latent heat transfer in the
clo seat
real environment, such as by the moisture flow from skin to contact area q . These mechanisms can be
evp
influenced by the use of mechanically induced air flow rates (e.g. seat ventilation, q - q ) or heat sources
air,out air,in
(e.g. seat heating, q ).
heat
This chapterclause describes an index for evaluating the thermal comfort of seats. A measure for the palm area
can be derived on the base of the contact temperature defined in ISO/TS 13732-2. This t evaluation
eq,cont
method is basically based on experiments with participants, but it can also be applied to evaluations using
thermal manikins, as described in Clause 7the previous chapter,, by replacing the evaporation effects of
perspiration on the seat contact surface with a theoretical model. This means a suitable theoretical sweating
model is available for evaluating t with a thermal manikin instead of a participant.
eq,cont
8.2 Calculation methodology
As can be seen from Figure 1Figure 1,, the calculation of t is based on the balance of heat flux densities at
eq,cont
an infinitesimal volume element (green area). The equivalent heat flux q [see Figure 1Figure 1 b), right-
eq,cont
hand side] depends on the heat fluxes in the real environment [see Figure 1Figure 1 b), left-hand side]
according to the equations in the centre of Figure 1Figure 1 b). The volume element is represented by node K
at which the energy balance is performed. Furthermore, K represents the contact interface between the human
body and any kind of contacting surface.
t
eq
t
r
q + q q
conv rad eq
𝑞𝑞 =𝑞𝑞 +𝑞𝑞
eq conv rad
t
t
skin skin
t ,
air
v
air
(a)
t , v
air air t
skin t
t
air t skin
seat
t
seat
q
eq,cont
𝑡𝑡 −𝑡𝑡
skin eq,cont
t
eq,cont
𝑞𝑞 =
eq,cont
𝑅𝑅
calib
≡𝑞𝑞 +𝑞𝑞
clo evp
q
heat
q
clo =𝑞𝑞 −𝑞𝑞 +𝑞𝑞
air,out air,in seat
q
seat
−𝑞𝑞
heat
𝑞𝑞
eq,cont
𝑅𝑅
calib
q
q – q
air,out air,in evp
𝑅𝑅 𝑡𝑡
seat 𝑅𝑅 𝑡𝑡 skin
clo eq,cont
(b)
a)
ISO/DISFDIS 14505-2:20252026(en)

b)
NOTE The teq,cont is described using a nodal energy balance at node K (left-hand side: heat fluxes in real environment,
right-hand side: heat flux in equivalent environment with a calibrated insulation value Rcalib).
Figure 1 — Specification and physical interpretation of the equivalent temperature (: a) and
equivalent contact temperature (b).
The energy balance at node K is described by Formula (17)Formula (17),, where negative quantities leave K
and positive ones enter K.
(17)
𝑞𝑞 +𝑞𝑞 −𝑞𝑞 +𝑞𝑞 −𝑞𝑞 +𝑞𝑞 = 0 (17)
𝑐𝑐𝑜𝑜𝑜𝑜 𝑒𝑒𝑒𝑒𝑒𝑒 𝑠𝑠𝑒𝑒𝑎𝑎𝑡𝑡 𝑎𝑎𝑑𝑑𝑟𝑟,𝑑𝑑𝑛𝑛 𝑎𝑎𝑑𝑑𝑟𝑟,𝑜𝑜𝑜𝑜𝑡𝑡 ℎ𝑒𝑒𝑎𝑎𝑡𝑡
where
qclo is the heat flux density through the clothing, in watts per square metre (W/m );
qevp is the heat flux density of the moisture flow through the clothing, in watts per square metre (W/m );
qseat is the heat flux density through the seat, in watts per square metre (W/m );
qair,in is the heat flux density of the incoming mass air flow by seat fan, in watts per square metre (W/m );
qair,out is the heat flux density of the outgoing mass air flow by seat fan, in watts per square metre (W/m );
qheat is the heat flux density of an optional internal heat source, in watts per square metre (W/m ).
Formulae 18 – 23 describe a simplified three-node model (Figure 1(Figure 1)) for seat integration. The air
mass flow is assumed to be 100 % efficient, with no short-circuit to ambient air. The incoming air temperature
is assumed equal to the ambient air temperature, and the outgoing air temperature is assumed equal to the
contact area temperature. These formulae are of theoretical character and are intended to illustrate the
approach. Manufacturer-dependent parameters, such as contact areas and electrical efficiencies, are not
specified. The heat flux densities in the real environment, visualized on the left-hand side of
Figure 1bFigure 1b are subsequently described with the heat flux density through the clothing layer q
clo
(Formula (18)(Formula (18)),), the evaporative heat flux density between skin and contact area q
evp
(Formula (19)(Formula (19)),), the conductive heat flux density through the seat q (Formula (20)(Formula
seat
(20)),), the outgoing heat flux density due to the seat ventilation q (Formula (21)(Formula (21))) as well
air,out
as the incoming heat flux density due to the seat ventilation q (Formula (22)(Formula (22))) and the heat
air,in
flux generated by the use of a heat source q (Formula (23)(Formula (23)). ).
heat
(18)
(19)
(20)
(21)
(22)
(23)
𝑡𝑡 −𝑡𝑡
𝑠𝑠𝑠𝑠𝑑𝑑𝑛𝑛 𝑛𝑛𝑜𝑜𝑑𝑑
𝑞𝑞 = (18)
𝑐𝑐𝑜𝑜𝑜𝑜
𝑅𝑅
𝑐𝑐𝑐𝑐𝑜𝑜
𝑠𝑠˙ ⋅(𝑟𝑟+𝑐𝑐 ⋅𝑡𝑡 )⋅(𝑥𝑥 −𝑥𝑥 )
𝑑𝑑𝑐𝑐 0 𝑃𝑃,𝑣𝑣𝑐𝑐𝑣𝑣 𝑠𝑠𝑠𝑠𝑑𝑑𝑛𝑛 𝑛𝑛𝑜𝑜𝑑𝑑 𝑜𝑜𝑛𝑛𝑣𝑣
𝑞𝑞 = (19)
𝑒𝑒𝑒𝑒𝑒𝑒
𝐴𝐴
𝑐𝑐𝑜𝑜𝑛𝑛𝑠𝑠
𝑡𝑡 −𝑡𝑡
𝑛𝑛𝑜𝑜𝑑𝑑 𝑜𝑜𝑛𝑛𝑣𝑣
𝑞𝑞 = (20)
𝑠𝑠𝑒𝑒𝑎𝑎𝑡𝑡
𝑅𝑅
𝑠𝑠𝑜𝑜𝑐𝑐𝑠𝑠
𝑚𝑚˙ ×(𝑐𝑐 ⋅𝑡𝑡 +𝑥𝑥 ⋅(𝑟𝑟 +𝑐𝑐 ⋅𝑡𝑡 ))
𝑑𝑑𝑎𝑎 𝑃𝑃,𝑑𝑑𝑎𝑎 𝑛𝑛𝑜𝑜𝑑𝑑 𝑛𝑛𝑜𝑜𝑑𝑑 0 𝑃𝑃,𝑒𝑒𝑎𝑎𝑒𝑒 𝑛𝑛𝑜𝑜𝑑𝑑
𝑞𝑞 =
𝑎𝑎𝑑𝑑𝑟𝑟,𝑜𝑜𝑜𝑜𝑡𝑡
𝐴𝐴
𝑐𝑐𝑜𝑜𝑛𝑛𝑡𝑡
(21)
𝑠𝑠˙ ⋅(𝑐𝑐 ⋅𝑡𝑡 +𝑥𝑥 ⋅(𝑟𝑟+𝑐𝑐 ⋅𝑡𝑡 ))
𝑑𝑑𝑐𝑐 𝑃𝑃,𝑑𝑑𝑐𝑐 𝑜𝑜𝑛𝑛𝑣𝑣 𝑜𝑜𝑛𝑛𝑣𝑣 0 𝑃𝑃,𝑣𝑣𝑐𝑐𝑣𝑣 𝑜𝑜𝑛𝑛𝑣𝑣
𝑞𝑞 = (22)
𝑎𝑎𝑑𝑑𝑟𝑟,𝑑𝑑𝑛𝑛
𝐴𝐴
𝑐𝑐𝑜𝑜𝑛𝑛𝑠𝑠
𝐴𝐴 𝑄𝑄
𝑐𝑐𝑜𝑜𝑛𝑛𝑡𝑡 𝑒𝑒𝑜𝑜
𝑞𝑞 = ⋅ ⋅𝜂𝜂
ℎ𝑒𝑒𝑎𝑎𝑡𝑡
𝐴𝐴 𝐴𝐴
𝑡𝑡𝑜𝑜𝑡𝑡 𝑡𝑡𝑜𝑜𝑡𝑡
(23)
where
Acont is the contacting surface area related to a person’s body, in square metres (m );
Atot is the total heated seat surface area, in square metres (m );
cp,vap is the specific heat capacity of water vapor (= 2 080 J/(kg K)), in joules per kilogram Kelvin [J/(kg K)];
cp,da is the specific heat capacity of dry air (= 1 005 J/(kg K)), in joules per kilogram Kelvin [J/(kg K)];
𝑚𝑚˙ is the mass flow rate generated by the seat fans, in kilograms per second (kg/s);
𝑑𝑑𝑎𝑎
Qel is the electrical power consumed by the seat heating, in watts (W);
r0 is the specific heat for vaporization of water (= 2 256 kJ/kg), in joules per kilogram (J/kg);
Rclo is the thermal resistance of the clothing combination, in square metres Kelvin per watt [(m K)/W];
Rseat is the thermal resistance of the seat or the contacting surface, in square metres Kelvin per watt [(m K)/W];
tenv is the ambient temperature, in degrees Celsius (°C);
tskin is the local skin temperature, in degrees Celsius (°C);
tnod is the contact area temperature in the real environment, in degrees Celsius (°C);
xenv is the specific humidity of the surrounding air, in kilograms per kilogram (kg/kg);
xnod is the specific humidity at contact area, in kilograms per kilogram (kg/kg);
η is the electrical efficiency of the seat heating (-).
If 𝑚𝑚˙ = 0 , evaporative heat (e.g. sweating and insensible perspiration) is ignored.
𝑑𝑑𝑎𝑎
ISO/DISFDIS 14505-2:20252026(en)
Replacing the single terms in Formula (17)Formula (17) by Formula (18)Formula (18) – Formula (23) to
Formula (23) and rearranging the terms, finally leads to Formula (24)Formula (24),, which holds the
mathematical model for the calculation of t .
nod
(24)
𝑚𝑚˙ ⋅(𝑥𝑥 −𝑥𝑥 )⋅𝑐𝑐
𝑑𝑑𝑎𝑎 𝑛𝑛𝑜𝑜𝑑𝑑 𝑒𝑒𝑛𝑛𝑒𝑒 𝑃𝑃,𝑒𝑒𝑎𝑎𝑒𝑒
( + )⋅𝑡𝑡
𝑠𝑠𝑠𝑠𝑑𝑑𝑛𝑛
𝑅𝑅 𝐴𝐴
𝑐𝑐𝑜𝑜𝑜𝑜 𝑐𝑐𝑜𝑜𝑛𝑛𝑡𝑡
𝑡𝑡 =
𝑛𝑛𝑜𝑜𝑑𝑑
𝑚𝑚˙ ⋅(𝑐𝑐 +𝑥𝑥 ⋅𝑐𝑐 )
1 1
𝑑𝑑𝑎𝑎 𝑃𝑃,𝑑𝑑𝑎𝑎 𝑛𝑛𝑜𝑜𝑑𝑑 𝑃𝑃,𝑒𝑒𝑎𝑎𝑒𝑒
+ +
𝑅𝑅 𝑅𝑅 𝐴𝐴
𝑐𝑐𝑜𝑜𝑜𝑜 𝑠𝑠𝑒𝑒𝑎𝑎𝑡𝑡 𝑐𝑐𝑜𝑜𝑛𝑛𝑡𝑡

𝑚𝑚˙ ⋅(𝑐𝑐 +𝑥𝑥 ⋅𝑐𝑐 )
𝑑𝑑𝑎𝑎 𝑃𝑃,𝑑𝑑𝑎𝑎 𝑒𝑒𝑛𝑛𝑒𝑒 𝑃𝑃,𝑒𝑒𝑎𝑎𝑒𝑒
( + )⋅𝑡𝑡 +𝑞𝑞
𝑒𝑒𝑛𝑛𝑒𝑒 ℎ𝑒𝑒𝑎𝑎𝑡𝑡
𝑅𝑅 𝐴𝐴
𝑠𝑠𝑒𝑒𝑎𝑎𝑡𝑡 𝑐𝑐𝑜𝑜𝑛𝑛𝑡𝑡
+
𝑚𝑚˙ ⋅(𝑐𝑐 +𝑥𝑥 ⋅𝑐𝑐 )
1 1
𝑑𝑑𝑎𝑎 𝑃𝑃,𝑑𝑑𝑎𝑎 𝑛𝑛𝑜𝑜𝑑𝑑 𝑃𝑃,𝑒𝑒𝑎𝑎𝑒𝑒
+ +
𝑅𝑅 𝑅𝑅 𝐴𝐴
𝑐𝑐𝑜𝑜𝑜𝑜 𝑠𝑠𝑒𝑒𝑎𝑎𝑡𝑡 𝑐𝑐𝑜𝑜𝑛𝑛𝑡𝑡
(24)
Since the equivalent heat flux depends on the heat fluxes in the real thermal environment, as described in
Figure 1Figure 1,, it can be calculated by application of the heat fluxes on the environmental-side or skin-
surface-side of the balance with Formula (25)Formula (25) or Formula (26)Formula (26),, respectively. R
calib
is a fixed, calibrated insulation value corresponding to a generally specified virtual clothing insulation.
(25)
(26)
𝑡𝑡 =𝑡𝑡 −𝑅𝑅 ⋅(𝑞𝑞 +𝑞𝑞 −𝑞𝑞 −𝑞𝑞 ) (25)
𝑒𝑒𝑒𝑒,𝑐𝑐𝑜𝑜𝑛𝑛𝑡𝑡 𝑠𝑠𝑠𝑠𝑑𝑑𝑛𝑛 𝑐𝑐𝑎𝑎𝑜𝑜𝑑𝑑𝑐𝑐 𝑠𝑠𝑒𝑒𝑎𝑎𝑡𝑡 𝑎𝑎𝑑𝑑𝑟𝑟,𝑜𝑜𝑜𝑜𝑡𝑡 𝑎𝑎𝑑𝑑𝑟𝑟,𝑑𝑑𝑛𝑛 ℎ𝑒𝑒𝑎𝑎𝑡𝑡
𝑡𝑡 =𝑡𝑡 −𝑅𝑅 ⋅(𝑞𝑞 +𝑞𝑞 ) (26)
𝑒𝑒𝑒𝑒,𝑐𝑐𝑜𝑜𝑛𝑛𝑡𝑡 𝑠𝑠𝑠𝑠𝑑𝑑𝑛𝑛 𝑐𝑐𝑎𝑎𝑜𝑜𝑑𝑑𝑐𝑐 𝑐𝑐𝑜𝑜𝑜𝑜 𝑒𝑒𝑒𝑒𝑒𝑒
where R is the virtual thermal resistance between t and t , in square metres Kelvin per watt
calib eq,cont skin
[(m K)/W].
x should be measured by experiments with participants, but it can also be estimated using a theoretical
nod
sweating model instead of a thermal manikin. As a result, it can also be used to evaluate air conditioning seats
of a blow-out type, which are difficult to measure with.
Annex A
(informative)
Examples of measuring instruments
A.1 Thermal manikins
A thermal manikin comprises a human-sized and -shaped sensor with its surface covered with numerous,
individually controlled, heated zones. It is suitable for measurement of whole body as well as local t . The
eq
independent zones of the manikin are heated to a controlled and measured temperature. Low-voltage power
is pulsed to each zone at a rate that allows the maintenance of a chosen constant or variable surface
temperature. It is also possible to maintain a constant power supply to the surface.
The power consumption under steady-state conditions is a measure of the convective, radiative and
conductive heat losses (dry heat loss). Measurements and regulation are made with a computer system.
Typically, the quantity measured for each zone is the power consumption or heat loss, Q (W/m ), and the
surface temperature, t (°C). The direct measurement of Q and t eliminates the need for determining the other
s s
components. By normalization to a climate according to the specification of equivalent temperature, the heat
loss can be converted to an equivalent temperature. The technical data of two manikins are presented in
Figure A.1Figure A.1 and Table A.1Table A.1. More details of the measurement and regulation system can be
[8] [10] [14]
found in Reference[8], Reference[10]reference , reference reference , Reference[14]and
[23]
Reference[23]reference .
IS
...

PROJET
Norme
internationale
ISO/DIS 14505-2
ISO/TC 159/SC 5
Ergonomie des ambiances
Secrétariat: BSI
thermiques — Évaluation des
Début de vote:
ambiances thermiques dans les
2025-05-01
véhicules —
Vote clos le:
2025-07-24
Partie 2:
Détermination de la température
équivalente
Ergonomics of the thermal environment — Evaluation of thermal
environments in vehicles —
Part 2: Determination of equivalent temperature
ICS: 13.180; 43.020
CE DOCUMENT EST UN PROJET DIFFUSÉ
POUR OBSERVATIONS ET APPROBATION. IL
EST DONC SUSCEPTIBLE DE MODIFICATION
ET NE PEUT ÊTRE CITÉ COMME NORME
INTERNATIONALE AVANT SA PUBLICATION EN
TANT QUE TELLE.
Le présent document est distribué tel qu’il est parvenu du secrétariat
du comité. OUTRE LE FAIT D’ÊTRE EXAMINÉS POUR
ÉTABLIR S’ILS SONT ACCEPTABLES À DES
FINS INDUSTRIELLES, TECHNOLOGIQUES ET
COMMERCIALES, AINSI QUE DU POINT DE VUE
DES UTILISATEURS, LES PROJETS DE NORMES
INTERNATIONALES DOIVENT PARFOIS ÊTRE
TRAITEMENT PARALLÈLE ISO/CEN
CONSIDÉRÉS DU POINT DE VUE DE LEUR
POSSIBILITÉ DE DEVENIR DES NORMES
POUVANT SERVIR DE RÉFÉRENCE DANS LA
RÉGLEMENTATION NATIONALE.
LES DESTINATAIRES DU PRÉSENT PROJET
SONT INVITÉS À PRÉSENTER, AVEC LEURS
OBSERVATIONS, NOTIFICATION DES DROITS
DE PROPRIÉTÉ DONT ILS AURAIENT
ÉVENTUELLEMENT CONNAISSANCE
ET À FOURNIR UNE DOCUMENTATION
EXPLICATIVE.
Numéro de référence
ISO/DIS 14505-2:2025(fr)
ISO/DIS 14505-2:2025(fr)
ISO/TC 159
Date : 2025-05-01
ISO/DIS 14505-2:2025(fr)
ISO/TC 159
Secrétariat : BSI
Ergonomie des ambiances thermiques — Évaluation des
ambiances thermiques dans les véhicules —
Partie 2 : Détermination de la température équivalente
Ergonomics of the thermal environment — Evaluation of thermal environments in vehicles —
Part 2: Determination of equivalent temperature

ICS : 13.180 ; 43.020
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2025
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publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique,
y compris la photocopie, ou la diffusion sur l’internet ou sur un intranet, sans autorisation écrite préalable. Une autorisation peut
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Langue du document:  F
ii
ISO/DIS 14505-2:2025(fr)
Sommaire Page
Avant-propos . iv
Introduction . v
1 Domaine d’application . 1
2 Références normatives . 1
3 Termes et définitions . 1
4 Principes d'évaluation . 3
4.1 Description générale de la température équivalente . 3
4.2 Principe général de détermination de la température équivalente . 4
5 Températures équivalentes spécifiques . 4
5.1 Généralités . 4
5.2 Température équivalente du corps dans son ensemble . 5
5.2.1 Principe de détermination . 5
5.2.2 Calcul . 5
5.3 Température équivalente segmentaire . 5
5.3.1 Principe de détermination . 5
5.3.2 Calcul . 6
5.4 Température équivalente directionnelle . 6
5.4.1 Principe de détermination . 6
5.4.2 Calcul . 7
5.5 Température équivalente omnidirectionnelle. 7
5.5.1 Principe de détermination . 7
5.6 Calcul . 8
6 Instruments de mesure . 8
7 Évaluation . 9
7.1 Détermination de la température équivalente du corps dans son ensemble . 9
7.1.1 Détermination avec des capteurs omnidirectionnels . 9
7.1.2 Détermination avec un mannequin thermique . 9
7.2 Détermination de la température équivalente locale . 9
7.2.1 Détermination avec des capteurs omnidirectionnels ou des capteurs plats chauffés . 9
7.2.2 Détermination avec un mannequin thermique . 10
8 Température de contact équivalente t . 10
eq,cont
(informative) Exemples d'instruments de mesure . 15
(informative) Caractéristiques et spécifications des instruments de mesure . 18
(informative) Étalonnage et autres déterminations . 24
(informative) Interprétation de la température équivalente . 26
(informative) Exemples . 31
Bibliographie. 35
iii
ISO/DIS 14505-2:2025(fr)
Avant-propos
L'ISO (Organisation internationale de normalisation) est une fédération mondiale d'organismes nationaux
de normalisation (comités membres de l'ISO). L'élaboration des Normes internationales est en général
confiée aux comités techniques de l'ISO. Chaque comité membre intéressé par une étude a le droit de faire
partie du comité technique créé à cet effet. Les organisations internationales, gouvernementales et non
gouvernementales, en liaison avec l'ISO participent également aux travaux. L'ISO collabore étroitement avec
la Commission électrotechnique internationale (IEC) en ce qui concerne la normalisation électrotechnique.
Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont décrites
dans les Directives ISO/IEC, Partie 1. Il convient, en particulier, de prendre note des différents critères
d'approbation requis pour les différents types de documents ISO. Le présent document a été rédigé
conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2
(voir www.iso.org/directives).
L'ISO attire l'attention sur le fait que la mise en application du présent document peut entraîner l'utilisation
d'un ou de plusieurs brevets. L'ISO ne prend pas position quant à la preuve, à la validité et à l'applicabilité
de tout droit de propriété revendiqué à cet égard. À la date de publication du présent document, l'ISO n'avait
pas reçu notification qu'un ou plusieurs brevets pouvaient être nécessaires à sa mise en application.
Toutefois, il y a lieu d'avertir les responsables de la mise en application du présent document que des
informations plus récentes sont susceptibles de figurer dans la base de données de brevets, disponible à
l'adresse www.iso.org/brevets. L'ISO ne saurait être tenue pour responsable de ne pas avoir identifié tout
ou partie de tels droits de brevet.
Les appellations commerciales éventuellement mentionnées dans le présent document sont données pour
information, par souci de commodité, à l'intention des utilisateurs et ne sauraient constituer un engagement.
Pour une explication de la nature volontaire des normes, la signification des termes et expressions
spécifiques de l'ISO liés à l'évaluation de la conformité, ou pour toute information au sujet de l'adhésion de
l'ISO aux principes de l'Organisation mondiale du commerce (OMC) concernant les obstacles techniques au
commerce (OTC), voir www.iso.org/avant-propos.
Le présent document a été élaboré par le comité technique ISO/TC 159, Ergonomie, sous-comité SC 5,
Ergonomie de l'environnement physique.
Cette deuxième édition annule et remplace la première édition (ISO 14505-2:2006), qui a fait l'objet d'une
révision technique.
Les principales modifications sont les suivantes :
— méthode d'évaluation des zones de contact (température de contact équivalente).
Une liste de toutes les parties de la série ISO 14505 se trouve sur le site web de l'ISO.
Il convient que l'utilisateur adresse tout retour d'information ou toute question concernant le présent
document à l'organisme national de normalisation de son pays. Une liste exhaustive desdits organismes se
trouve à l'adresse www.iso.org/fr/members.html.
iv
ISO/DIS 14505-2:2025(fr)
Introduction
L'interaction entre les échanges thermiques par convection, par rayonnement et par conduction à l'intérieur
d'un habitacle de véhicule ou dans des espaces confinés analogues est très complexe. Les charges thermiques
extérieures associées au système de chauffage et de ventilation intérieure du véhicule créent un
l’environnement thermique local qui peut varier de façon significative dans l'espace et dans le temps. Des
conditions thermiques asymétriques se produisent et celles-ci sont souvent la principale cause de plaintes
d'inconfort thermique. Dans les véhicules ne disposant pas d'un système de chauffage, de ventilation et de
climatisation (système CVCA) ou dans lesquels ce système fonctionne de façon médiocre, la contrainte
thermique est déterminée en général par l'impact des conditions climatiques ambiantes sur l'habitacle du
véhicule. Une évaluation subjective est par nature intégratrice, car l'individu regroupe en une réaction l'effet
combiné de plusieurs stimuli thermiques. Cependant, elle n'est pas suffisamment détaillée et précise pour
une utilisation répétée. Les mesures physiques fournissent des informations détaillées et précises, mais
nécessitent une intégration pour prévoir les effets thermiques sur l'homme. Étant donné que plusieurs
facteurs climatiques influencent le bilan thermique définitif d'une personne, une mesure intégrée de ces
facteurs, respectant leur degré d'importance relative, s'avère nécessaire. La présente norme comprend les
modèles de température équivalente t pour l'évaluation des conditions thermiques. Pour une
eq
considération particulière du siège, la température de contact équivalente t peut être appliquée pour
eq,cont
les compartiments du corps en contact avec les surfaces.

v
PROJET de Norme internationale ISO/DIS 14505-2:2025(fr)

Ergonomie des ambiances thermiques — Évaluation des
ambiances thermiques dans les véhicules —
Partie 2 : Détermination de la température équivalente
1 Domaine d’application
La présente partie de l'ISO 14505 donne des lignes directrices relatives à l'évaluation des conditions
thermiques à l'intérieur d'un habitacle de véhicule. Elle peut également s'appliquer à d'autres espaces
confinés où règnent des conditions climatiques asymétriques. Elle est essentiellement destinée à
l'évaluation des conditions thermiques, lorsque les écarts par rapport à la neutralité thermique sont
relativement faibles. L'une des méthodes appropriées décrites dans la présente partie de l'ISO 14505
peut être choisie pour être incluse dans des normes de performance spécifiques en vue de soumettre à
essai les systèmes de chauffage, de ventilation et de climatisation (système CVCA) des véhicules et les
espaces confinés analogues.
2 Références normatives
Les documents suivants sont cités dans le texte de sorte qu'ils constituent, pour tout ou partie de leur
contenu, des exigences du présent document. Pour les références datées, seule l'édition citée s'applique.
Pour les références non datées, la dernière édition du document de référence s'applique (y compris les
éventuels amendements).
ISO 13731, Ergonomie des ambiances thermiques — Vocabulaire et symboles
3 Termes et définitions
Pour les besoins du présent document, les termes et les définitions de l'ISO 13731 ainsi que les suivants
s'appliquent.
L'ISO et l'IEC tiennent à jour des bases de données terminologiques destinées à être utilisées en
normalisation, consultables aux adresses suivantes :
— ISO Online browsing platform : disponible à l’adresse https://www.iso.org/obp
— IEC Electropedia : disponible à l'adresse https://www.electropedia.org/
3.1
température équivalente t
eq
température d'un espace homogène, dont la température moyenne de rayonnement est égale à la
température de l'air et où la vitesse de l'air est égale à zéro, dans lequel une personne échange la même
déperdition de chaleur par convection et par rayonnement que dans les conditions réelles soumises à
évaluation
3.2
température équivalente du corps dans son ensemble t
eq,whole
température d'une enceinte imaginaire, dont la température des surfaces environnantes est égale à la
température de l'air et où la vitesse de l'air est égale à zéro, dans laquelle un capteur chauffé, de forme
humaine, grandeur nature, échangera la même chaleur sèche par rayonnement et par convection que
dans le véritable environnement non uniforme
ISO/DIS 14505-2:2025(fr)
3.3
température équivalente segmentaire t
eq,segment
température uniforme d'une enceinte imaginaire, dont la température des surfaces environnantes est
égale à la température de l'air et où la vitesse de l'air est égale à zéro, dans laquelle une ou plusieurs zones
sélectionnées d'un mannequin thermique échangeront la même chaleur sèche par rayonnement et par
convection que dans le véritable environnement non uniforme
3.4
température équivalente directionnelle t
eq,direct
température uniforme d'une enceinte imaginaire, dont la température des surfaces environnantes est
égale à la température de l'air et où la vitesse de l'air est égale à zéro, dans laquelle une petite surface
plate et chauffée échangera la même chaleur sèche par rayonnement et par convection que dans le
véritable environnement non uniforme
3.5
température équivalente omnidirectionnelle t
eq,omni
température uniforme d'une enceinte imaginaire, dont la température des surfaces environnantes est
égale à la température de l'air et où la vitesse de l'air est égale à zéro, dans laquelle un ellipsoïde chauffé
échangera la même chaleur sèche par rayonnement et par convection que dans le véritable
environnement non uniforme
3.6
température de contact équivalente t
eq,cont
température uniforme d'une surface de contact imaginaire, à une vitesse d'air ambiante proche de zéro,
à laquelle une personne échangera la même quantité de chaleur sèche par conduction thermique pour
une isolation de vêtements virtuels que dans l'environnement réel non uniforme, où la personne éprouve
un transfert de chaleur sensible et latent aux parties du corps considérées
3.7
segment
partie d'un capteur de forme humaine correspondant en général à une partie réelle du corps, constituée
d'une ou plusieurs zones entières pour lesquelles une température équivalente segmentaire, t , est
eq,segment
déterminée
3.8
zone
division physique d'un mannequin, régulée de manière indépendante, à l'intérieur de laquelle sont
mesurés la température de surface et l'échange de chaleur
3.9
système CVCA
système de chauffage, ventilation et climatisation d'air du véhicule et/ou de l'habitacle
ISO/DIS 14505-2:2025(fr)
4 Principes d'évaluation
Le principe d'évaluation est fondé sur le mesurage de la température équivalente. La température
équivalente fournit une estimation physique unifiée des effets climatiques sur l'échange de chaleur sèche
du corps humain. En se basant sur la valeur réelle de la température équivalente et sur la variation de
celle-ci, il est possible de prévoir les conditions propices à un équilibre thermique dans les conditions
régnant dans la zone de neutralité thermique ou proches de celle-ci. La sensation thermique des
personnes est influencée principalement par des niveaux locaux et généraux et par des variations de flux
de chaleur au niveau de la surface cutanée. Les valeurs de la température équivalente d'un
environnement défini se sont révélées étroitement liées aux votes de sensation thermique des personnes
exposées au même environnement. Cela peut être utilisé pour l'interprétation de la valeur de t et
eq
l'évaluation de la qualité de l'environnement.
L’environnement thermique est évalué en termes de température équivalente totale, qui décrit le niveau
de neutralité thermique.
L’environnement thermique est également évalué au niveau des effets locaux sur des parties définies de
la surface du corps humain. Les températures équivalentes locales déterminent dans quelle mesure les
véritables parties du corps subissent des déperditions de chaleur demeurant dans des limites acceptables
(inconfort local).
4.1 Description générale de la température équivalente
La température équivalente est une grandeur physique pure qui intègre les effets indépendants de la
convection et du rayonnement sur l'échange de chaleur du corps humain. L'échange de chaleur globale
(corps dans son ensemble) fournit la meilleure description de ce rapport. Pour les rapports entre
l'échange de chaleur sèche locale et la température équivalente locale, l'expérience acquise est limitée.
La définition normalisée de la t s'applique uniquement au corps dans son ensemble. Il faut donc modifier
eq
la définition pour les besoins de la présente partie de l'ISO 14505. La t ne prend pas en compte la
eq
perception et la sensation humaines ou d'autres aspects subjectifs. Cependant, des études empiriques
montrent que les valeurs de t sont étroitement liées à la perception subjective de l'effet thermique.
eq
ISO/DIS 14505-2:2025(fr)
4.2 Principe général de détermination de la température équivalente
La détermination de la t est basée sur des équations relatives au transfert de chaleur par convection et
eq
par rayonnement pour des personnes vêtues. L'échange de chaleur par conduction est supposé faible et
est calculé en fonction du rayonnement et de la convection :
R=×h (t − t ) (1)
r sk r
C = h × t − t (2)
( )
c sk a
où
R
est l'échange de chaleur par rayonnement, en watts par mètre carré (W/m ) ;
C
est l'échange de chaleur par convection, en watts par mètre carré (W/m ) ;
h est le coefficient de transfert de chaleur par rayonnement, en watts par mètre carré degré Celsius
r
[W/(m °C)] ;
h est le coefficient de transfert de chaleur par convection, en watts par mètre carré degré Celsius
c
[W/(m °C)] ;
t est la température cutanée, en degrés Celsius (°C) ;
sk
t
est la température moyenne de rayonnement, en degrés Celsius (°C) ;
r
t est la température de l'air ambiant, en degrés Celsius (°C).
a
Dans la pratique, la température équivalente est déterminée et définie par :
Q
tt= − (3)
eq s
h
cal
où
t est la température de surface, en degrés Celsius (°C) ;
s
t est la température de l'environnement normalisé, en degrés Celsius (°C) ;
eq
Q est la déperdition de chaleur par convection et par rayonnement mesurée dans les conditions
réelles, en watts par mètre carré (W/m ) :
Q=+R C
(4)
h est le coefficient combiné de transfert de chaleur, déterminé lors de l'étalonnage dans un
cal
environnement normalisé, en watts par mètre carré degré Celsius [W/(m °C)].
L'environnement normalisé comprend des conditions thermiques uniformes et homogènes avec t = t
a
r
et la vitesse de l'air, v < 0,1 m/s. Un mode opératoire d'étalonnage approprié est décrit dans l'Annexe C.
a
5 Températures équivalentes spécifiques
5.1 Généralités
Étant donné qu'il n'existe aucune méthode pour mesurer la t totale réelle ou locale, quatre températures
eq
équivalentes spécifiques sont calculées en fonction de différents principes de mesurage décrits en 5.2 à
5.5. En fonction de différents principes de mesurage, ces températures sont définies comme suit :
1. température équivalente du corps dans son ensemble ;
ISO/DIS 14505-2:2025(fr)
2. température équivalente segmentaire ;
3. température équivalente directionnelle ;
4. température équivalente omnidirectionnelle.
5.2 Température équivalente du corps dans son ensemble
5.2.1 Principe de détermination
Le principe de la détermination consiste à mesurer le flux total de chaleur émise d'un mannequin d'essai
de taille humaine comprenant plusieurs zones, chacune avec une température de surface mesurée
spécifique similaire à celle d'un être humain. Théoriquement, la température équivalente du corps dans
son ensemble peut être mesurée avec des mannequins thermiques ou un nombre important de capteurs
plats chauffés attachés à un mannequin non chauffé. L'exactitude du résultat est fonction de la
température de surface, de la taille du corps, du nombre de zones et leur division, de la posture, etc. Une
méthode appropriée consiste à utiliser un mannequin thermique divisé en zones distinctes, chauffées
individuellement, couvrant l'ensemble du corps, avec des températures de surface proches de celles d'un
véritable être humain. Un mannequin de taille humaine avec seulement une zone ne permettra pas de
déterminer une t réaliste d'un corps dans son ensemble, car les conditions thermiques varient trop sur
eq
toute la surface. Plus il y a de zones sur le mannequin, plus la valeur mesurée sera correcte.
5.2.2 Calcul
Q
whole
tt= − (5)
eq,whole sk,whole
h
cal,whole
(tA )
sk,n n

t = (6)
sk,whole
A
n

QA
( )
 nn
Q = (7)
whole
A
 n
où
A est une fonction de pondération basée sur l'aire de surface ;
h est déterminé par étalonnage dans un environnement normalisé (voir Annexe C) ;
cal,whole
n est le nombre de zones du corps (0 < n ≤ N).
Pour pouvoir comparer les résultats obtenus d'autres mannequins, il convient que la valeur de t
eq
mesurée soit présentée avec les spécifications du mannequin utilisé, telles que le principe de régulation,
la température cutanée, le nombre de zones, etc. (voir Annexes A et B).
5.3 Température équivalente segmentaire
5.3.1 Principe de détermination
Le principe de la détermination consiste à mesurer le flux total de chaleur émise d'un segment
comprenant une ou plusieurs zones, chacune avec une température de surface mesurée spécifique
similaire à celle d'un être humain.
ISO/DIS 14505-2:2025(fr)
La t segmentaire est basée sur le flux de chaleur émise par une certaine partie du corps, c'est-à-dire un
eq
segment, comme la main, la tête ou la poitrine. La t segmentaire peut seulement être mesurée à l'aide
eq
d'un capteur chauffé de forme humaine, grandeur nature, par exemple un mannequin thermique. Il faut
que le nombre de zones et leur répartition correspondent au moins au segment réel pour lequel il
convient que la t segmentaire soit mesurée. Pour certains segments, par exemple la cuisse, il est
eq
nécessaire de diviser en au moins deux zones à l'intérieur du même segment, car les conditions
thermiques sont différentes sur la face avant et la face arrière (contact avec le siège) de la cuisse.
5.3.2 Calcul
Q
segment
(8)
tt= −
eq,segment sk,segment
h
cal,segment
tA
( )
sk,n n

t = (9)
sk,segment
A
 n
QA
( )
 nn
Q = (10)
segment
A

n
où
hcal,segment est déterminé par étalonnage dans un environnement normalisé (voir Annexe C) ;
n est le nombre de zones du corps (0 < n ≤ N).
Le segment peut être choisi librement mais il faut qu'il comprenne une ou plusieurs zones entières.
Normalement, les parties du corps telles la tête, les mains, les bras, les pieds, la poitrine, le dos et le
postérieur sont choisies. Pour pouvoir comparer les résultats obtenus avec d'autres mesurages, il
convient que la valeur de t mesurée soit présentée avec les spécifications sur le segment utilisé, telles
eq
que le principe de régulation, la température de surface, la partie du corps, le nombre, la taille et la
division des zones du segment (voir Annexes A et B).
5.4 Température équivalente directionnelle
5.4.1 Principe de détermination
Le principe de la détermination est de mesurer le flux total de chaleur émise d'une petite surface plate
avec une température de surface mesurée. La teq directionnelle peut être décrite comme un vecteur
normal au plan de mesurage en chaque point, défini par l'ampleur et la direction. Elle se rapporte à
l'échange de chaleur à l'intérieur de la demi-sphère à l'avant du plan infinitésimal. La t directionnelle
eq
peut seulement être mesurée à l'aide d'un capteur plat, lequel peut ou peut ne pas être attaché à un
mannequin chauffé ou autre dispositif de positionnement. Plusieurs capteurs peuvent être utilisés
simultanément pour déterminer la t directionnelle à d'autres emplacements ou dans d'autres
eq
directions, à condition qu'ils soient positionnés de manière à ne pas avoir d'incidence les uns sur les
autres.
ISO/DIS 14505-2:2025(fr)
5.4.2 Calcul
Q
direct
tt= − (11)
eq,direct sk,direct
h
cal,direct
où
t est la température de surface du capteur ;
sk,direct
Q est le flux de chaleur émise par le capteur ;
direct
h est déterminé par étalonnage du capteur dans un environnement normalisé (voir
cal,direct
Annexe C).
Une température équivalente locale, t , peut être calculée sous forme d'une valeur moyenne à partir
eq,local
de plusieurs mesurages effectués au même emplacement mais dans différentes directions. Elle peut être
calculée sous forme d'une moyenne arithmétique sans fonction de pondération (équation 12) ou avec
pondération (équation 13) afin de simuler une posture particulière du corps :
t
 eq,direct,n
(12)
t =
eq,local
n
où n est le nombre de directions :
t = t  A (13)
( )
eq,local eq,direct,nn

où n est le nombre de mesurages avec Σ(A ) = 1 et A représente des postures corporelles.
n
Une température équivalente totale peut être calculée sous forme d'une moyenne pondérée de
températures équivalentes locales :
t = t  A (14)
( )
eq,total  eq,local,nn
où n est le nombre d'emplacements avec Σ(A ) = 1.
n
Pour pouvoir comparer les résultats obtenus avec d'autres mesurages, il convient que la valeur de t
eq
mesurée soit présentée avec les spécifications sur le capteur utilisé, telles que le principe de régulation,
la température de surface, la taille ainsi que l'emplacement et la direction du capteur (voir Annexes A
et B). La t du corps dans son ensemble et la t totale n'est pas la même. Dans un environnement
eq eq
thermique asymétrique et avec contact avec le siège, la différence sera considérable.
5.5 Température équivalente omnidirectionnelle
5.5.1 Principe de détermination
Le principe de la détermination est de mesurer le flux total de chaleur émise par la surface d'un ellipsoïde
avec une température de surface mesurée. La t omnidirectionnelle peut être décrite comme la valeur
eq
moyenne pondérée de la t directionnelle dans toutes les directions. Les fonctions de pondération pour
eq
les différentes directions dépendent de la forme de l'ellipsoïde. Elle se rapporte à l'échange de chaleur
dans toutes les directions. La t omnidirectionnelle peut seulement être mesurée à l'aide d'un capteur
eq
ellipsoïdal avec un flux de chaleur uniforme sur toute la surface. Un ou plusieurs capteurs peuvent être
utilisés simultanément. En cas d'utilisation de plusieurs capteurs, il faut signaler que, en tant que surfaces
chaudes, les capteurs auront une incidence les uns sur les autres dans la sphère soumise au mesurage.
ISO/DIS 14505-2:2025(fr)
5.6 Calcul
Q
omni
tt= − (15)
eq,omni sk,omni
h
cal,omni
où
t est la température de surface du capteur ;
sk,omni
Q est le flux de chaleur émise par le capteur ;
omni
h est déterminé par étalonnage du capteur dans un environnement normalisé (voir
cal,omni
Annexe C).
La teq omnidirectionnelle déterminée à l'aide d'un capteur ellipsoïdal dans un environnement thermique
asymétrique est une t locale. Une t totale peut être calculée sous forme d'une moyenne arithmétique
eq eq
à partir de capteurs positionnés à différents emplacements avec des fonctions de pondération pour
différentes parties du corps conformément à la SAE J 2234 :
t =t A
(16)
( )
eq,total eq,local ,n n
où n est le nombre d'emplacements avec Σ(A ) = 1.
n
Pour pouvoir comparer les résultats obtenus avec d'autres mesurages, il convient que la valeur de t
eq
mesurée soit présentée avec les spécifications sur le capteur utilisé, telles que le principe de régulation,
la température de surface, la taille ainsi que l'emplacement et la direction du capteur (voir Annexes A
et B).
6 Instruments de mesure
Plusieurs méthodes et instruments de mesure, représentant différents principes de mesurage, sont
décrits dans les Annexes A et B. En fonction des besoins, il convient de choisir l'une quelconque des
méthodes décrites dans l'Annexe A.
Les valeurs de mesurage obtenues avec des méthodes dont le principe diffère ne sont pas comparables
entre elles. Elles correspondent à différents niveaux en termes de :
— fiabilité ;
— pertinence ;
— validité ;
— répétabilité ;
— précision ;
— intégration ;
— complexité ;
— coûts ; et
— disponibilité.
La performance et les exigences des méthodes spécifiques sont données dans l'Annexe B. Les exigences
relatives au mode opératoire d'étalonnage figurent dans l'Annexe C.
ISO/DIS 14505-2:2025(fr)
7 Évaluation
La température équivalente correspond à une évaluation quantitative des conditions propices à un
échange de chaleur physique. La valeur numérique de t est un niveau de température qui peut se
eq
rapprocher de températures ambiantes escomptées « normales ». Des valeurs t plus élevées indiquent
eq
des déperditions de chaleur inférieures (« plus chaud ») et des valeurs t plus faibles indiquent des
eq
déperditions de chaleur supérieures (« plus froid »).
L'interprétation de la température équivalente en termes de sensation thermique perçue anticipée est
basée sur une série d'expérimentations avec des participants pour lesquels les différents types de
température équivalente ont été mesurés. Des exemples d'interprétation sont décrits dans l'Annexe C.
Pour certains types de température équivalente, il n'existe pas de données pour comparaison avec des
réponses humaines. Néanmoins, ces types de mesurages peuvent être utilisés pour des mesurages
différentiels des conditions thermiques.
7.1 Détermination de la température équivalente du corps dans son ensemble
Il convient d'effectuer la détermination de la température équivalente du corps dans son ensemble à
l'aide de mesurages faits avec un mannequin thermique ou par intégration de mesurages discrets faits à
l'aide de capteurs omnidirectionnels placés en des emplacements définis à l'intérieur de l'habitacle du
véhicule.
7.1.1 Détermination avec des capteurs omnidirectionnels
Les capteurs omnidirectionnels sont décrits dans les Annexes A et B. Les capteurs sont installés sur un
support simulant une personne et placés sur un siège du véhicule. Six capteurs au minimum sont placés
en des emplacements pertinents et les mesurages sont effectués une fois un état d'équilibre atteint.
La température équivalente du corps dans son ensemble est déterminée comme la moyenne pondérée
en fonction de la superficie des capteurs individuels. Il convient de procéder à l'interprétation des valeurs
selon les directives données dans l'Annexe D.
7.1.2 Détermination avec un mannequin thermique
Les exigences relatives aux mannequins et aux modes opératoires sont décrites dans les Annexes A et B.
Le mannequin est placé sur le siège du véhicule et la déperdition de chaleur du corps dans son ensemble
est mesurée une fois un état d'équilibre atteint. La déperdition de chaleur du corps dans son ensemble
est la moyenne pondérée en fonction de la superficie des segments indépendants du mannequin. Il
convient de procéder à l'interprétation des valeurs selon les directives données dans l'Annexe D.
7.2 Détermination de la température équivalente locale
Il convient d'effectuer la détermination de la température équivalente du corps dans son ensemble à
l'aide de mesurages faits avec un mannequin thermique ou par intégration de mesurages discrets faits à
l'aide de capteurs omnidirectionnels
7.2.1 Détermination avec des capteurs omnidirectionnels ou des capteurs plats chauffés
Les capteurs omnidirectionnels sont décrits dans l'Annexe A. Les capteurs sont installés sur un support
simulant une personne et placés sur un siège du véhicule ou en des endroits définis sur la surface des
vêtements d'une personne ou d'un mannequin. Les mesurages sont effectués une fois un état d'équilibre
atteint. La température équivalente locale est déterminée comme la valeur du capteur individuel. Plus le
nombre de capteurs présents dans l'espace est important, meilleure sera la résolution de la variation du
champ thermique entourant le corps humain.
ISO/DIS 14505-2:2025(fr)
7.2.2 Détermination avec un mannequin thermique
Les exigences relatives aux mannequins et aux modes opératoires sont décrites dans les Annexes A et B.
Le mannequin est placé sur le siège du véhicule et la déperdition de chaleur est mesurée dans un segment
local du mannequin une fois un état d'équilibre atteint. La température équivalente locale est déterminée
par la valeur mesurée du segment individuel et correspond à ce segment particulier seulement. Il
convient de procéder à l'interprétation des valeurs selon les directives données dans l'Annexe D.
8 Température de contact équivalente t
eq,cont
L'échange de chaleur entre une personne et une surface en contact par conduction thermique ainsi que
par humidité n'est pas négligeable et a une influence significative sur la sensation thermique. Le calcul de
la température de contact équivalente teq,cont est basé sur les équations de la conduction thermique ainsi
que sur un échange thermique latent et sensible entre une personne vêtue et les surfaces en contact.
Comme indiqué à la Figure 1, les principes de définition de la température de contact équivalente t
eq,cont
et de la température équivalente t sont similaires et dépendent tous deux de la vitesse de l'air v dans
eq air
l'environnement réel. Dans le modèle de température équivalente, le flux de chaleur équivalent q
eq
dépend des flux de chaleur par convection q et par rayonnement q dans l'environnement réel avec
conv rad
la température de rayonnement t , la température de l'air t et la température de la peau t
r air skin
déterminées. La température de contact équivalente t comprend la description détaillée de la
eq,cont
situation thermodynamique à l'interface de contact entre un siège et la surface du corps humain. Ici, le
flux de chaleur équivalent q dépend de l'effet combiné de la conduction thermique à travers les
eq,cont
vêtements q et le siège q ainsi que de la variation de l'enthalpie due au transfert de chaleur sensible
clo seat
et latent dans l'environnement réel, par exemple par le flux d'humidité de la peau à la zone de contact
q . Ces mécanismes peuvent être influencés par l'utilisation de débits d'air induits mécaniquement (par
evp
exemple ventilation du siège, q - q ) ou de sources de chaleur (par exemple chauffage du siège,
air,out air,in
q ).
heat
Cet article donne des indications pour l'évaluation du confort thermique des sièges. Cette méthode
d'évaluation est principalement basée sur des expériences avec des participants, mais elle peut
également être appliquée aux évaluations utilisant des mannequins thermiques, comme décrit dans les
paragraphes précédents, en remplaçant les effets d'évaporation de la transpiration sur la surface de
contact du siège par un modèle théorique. Cela signifie qu'un modèle théorique de transpiration adapté
est disponible pour l'évaluation de t avec un mannequin thermique à la place d'un participant.
eq,cont
Méthodologie de calcul :
Comme le montre la Figure 1, le calcul de t est fondé sur l'équilibre des densités de flux de
eq,cont
chaleurdans un élément de volume infinitésimal (zone verte). Le flux de chaleur équivalent q
eq,cont
(Figure 1b, côté droit) s’exprime à partir des flux de chaleur dans l'environnement réel (Figure 1b, côté
gauche) selon les équations du centre de la Figure 1b. L'élément de volume est représenté par le nœud K
où le bilan énergétique est effectué. De plus, K représente l'interface de contact entre le corps humain et
tout type de surface de contact.
ISO/DIS 14505-2:2025(fr)
Figure 1 — Définition et interprétation physique de la température équivalente (a) et de la
température de contact équivalente (b). La t est décrite à l'aide d'un bilan énergétique au
eq,cont
nœud K (côté gauche : flux de chaleur en environnement réel, côté droit : flux de chaleur en
environnement équivalent avec une valeur d'isolation étalonnée R ).
calib
ISO/DIS 14505-2:2025(fr)
Le bilan énergétique au nœud K est décrit par (17), où les quantités négatives quittent K et les valeurs
positives y entrent :
q +q−−q +q q +q =0 (17)
clo evp seat air,in air,out heat
où
q est la densité du flux de chaleur à travers le vêtement, en watts par mètre carré (W/m ) ;
clo
q est la densité de flux de chaleur du flux d'humidité à travers le vêtement, en watts par mètre
evp
carré (W/m ) ;
q est la densité du flux de chaleur à travers le siège, en watts par mètre carré (W/m ) ;
seat
q est la densité de flux de chaleur du débit massique d'air entrant par le ventilateur du siège, en
air,in
watts par mètre carré (W/m ) ;
q est la densité du flux de chaleur du débit massique d'air sortant par ventilateur du siège, en
air,out
watts par mètre carré (W/m ) ;
q est la densité de flux de chaleur d'une source de chaleur interne facultative, exprimée en watts
heat
par mètre carré (W/m ).
ISO/DIS 14505-2:2025(fr)
De là, les densités de flux de chaleur dans l'environnement réel, visualisées sur le côté gauche de la
Figure 1b sont décrites par la densité de flux de chaleur à travers la couche de vêtements q (18), la
clo
densité de flux de chaleur par évaporation entre la peau et la zone de contact q (19), la densité de flux
evp
de chaleur par conduction dans le siège q (20), la densité de flux de chaleur sortant due à la ventilation
seat
du siège q (21) ainsi que la densité de flux de chaleur entrant due à la ventilation du siège q (22)
air,out air,in
et le flux de chaleur généré par l'utilisation d'une source de chaleur q (23) :
heat
tt−
skin nod
q= (18)
clo
R
clo
m  r +c t  x − x
( ) ( )
da 0 P,vap skin nod env
q= (19)
evp
A
cont
tt−
nod env
q= (20)
seat
R
seat
m × c t + x (r +c t )
( )
da P,da nod nod 0 P,vap nod
q= (21)
air,out
A
cont
m  c t + x (r +c t )
( )
da P,da env env 0 P,vap env
q= (22)
air,in
A
cont
AQ
cont el
q=  (23)
heat
AA
tot tot
où
²
A est l'aire de surface de contact liée au corps d'une personne, en mètres carrés (m ) ;
cont
²
A est l'aire de surface totale du siège chauffant, en mètres carrés (m ) ;
tot
c est la puissance calorifique spécifique de la vapeur d'eau (= 2 080 J/(kg °C)), en joules par
p,vap
kilogramme degré Celsius [J/(kg °C)] ;
c est la puissance calorifique spécifique de l'air sec (= 1 005 J/(kg °C)), en joules par kilogramme
p,da
degré Celsius [J/(kg °C)] ;
est le débit massique généré par les ventilateurs du siège, en kilogrammes par seconde (kg/s) ;
m
da
Q est l'électricité consommée par le chauffage du siège, exprimée en watts (W) ;
el
r est la chaleur spécifique pour la vaporisation de l'eau (= 2 256 kJ/kg), en joules par
kilogramme (J/kg) ;
R est la résistance thermique de la combinaison de vêtements, en mètres carrés-degré Celsius
clo
par watt [(m °C)/W] ;
R est la résistance thermique du siège ou de la surface de contact, en mètres carrés-degré Celsius
seat
par watt [(m °C)/W] ;
t est la température ambiante, en degrés Celsius (°C) ;
env
t est la température cutanée locale, en degrés Celsius (°C) ;
skin
t est la température de surface de contact dans l'environnement réel, en degrés Celsius (°C) ;
nod
x est l'humidité spécifique de l'air environnant, en kilogrammes par kilogramme (kg/kg) ;
env
x est l'humidité spécifique à la zone de contact, en kilogrammes par kilogramme (kg/kg) ;
nod
est le rendement électrique du chauffage du siège (-).
η
ISO/DIS 14505-2:2025(fr)
Si m = 0 , la chaleur par évaporation (par exemple transpiration et transpiration insensible) est ignorée.
da
En remplaçant les termes de (17) par les équations (18) - (23) et en réorganisant les termes, cela conduit
finalement à (24), qui contient le modèle mathématique pour le calcul de t :
nod
m ( x − x )c

da nod env P,vap
+ t
...