EN ISO 7730:2025
(Main)Ergonomics of the thermal environment - Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort criteria (ISO 7730:2025)
Ergonomics of the thermal environment - Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort criteria (ISO 7730:2025)
This document specifies a method to evaluate the general thermal comfort of people in a space and the degree of discomfort (thermal dissatisfaction) of people exposed to moderate thermal environments. It defines the analytical determination and interpretation of thermal comfort using calculation of predicted mean vote (PMV) and predicted percentage of dissatisfied (PPD) and local thermal comfort criteria, giving the environmental conditions considered acceptable for general thermal comfort as well as those representing local discomfort.
It is applicable to healthy men and women exposed to indoor environments where thermal comfort is desirable, but where moderate deviations from thermal comfort occur, in the design of new environments or the assessment of existing ones.
Although developed specifically for the work environment, this document is applicable to other kinds of environment as well.
Ergonomie der thermischen Umgebung - Analytische Bestimmung und Interpretation der thermischen Behaglichkeit durch Berechnung des PMV- und des PPD-Indexes und Kriterien der lokalen thermischen Behaglichkeit (ISO 7730:2025)
Dieses Dokument legt ein Verfahren fest, mit dem sich die allgemeine thermische Behaglichkeit von Personen in einem Raum sowie der Grad der Unbehaglichkeit (thermischen Unzufriedenheit) von Personen, die einem gemäßigten Umgebungsklima ausgesetzt sind, bewerten lassen. Es trifft Festlegungen zur analytischen Bestimmung und Interpretation der thermischen Behaglichkeit mithilfe der Berechnung von PMV (en: predicted mean vote) und PPD (en: predicted percentage of dissatisfied) und anhand von Kriterien für die lokale thermische Behaglichkeit, wobei die Umgebungsbedingungen angegeben werden, die für die allgemeine thermische Behaglichkeit als annehmbar gelten, und die Umgebungsbedingungen, bei denen lokale Unbehaglichkeit auftritt.
Es ist anwendbar für gesunde Männer und Frauen, die einem Innenraumklima ausgesetzt sind, das thermische Behaglichkeit hervorrufen soll, wo es jedoch bei der Gestaltung neuer bzw. der Bewertung existierender Umgebungen zu moderaten Abweichungen vom Zustand der thermischen Behaglichkeit kommt.
Obwohl dieses Dokument speziell für die Arbeitsumgebung erstellt wurde, kann es auch für andere Arten der Umgebung angewendet werden.
Ergonomie des ambiances thermiques - Détermination analytique et interprétation du confort thermique par le calcul des indices PMV et PPD et par des critères de confort thermique local (ISO 7730:2025)
Le présent document spécifie une méthode d’évaluation du confort thermique général des personnes présentes dans un espace et du degré d’inconfort (insatisfaction thermique) des personnes exposées à des ambiances thermiques modérées. Il définit comment déterminer analytiquement et interpréter le confort thermique, par le calcul du vote moyen prévisible (indice PMV) et du pourcentage prévisible d’insatisfaits (indice PPD), et par des critères de confort thermique local, donnant les conditions d’environnement considérées acceptables du point de vue du confort thermique général et les conditions représentant les inconforts locaux.
Il s’applique aux hommes et aux femmes en bonne santé, exposés à des ambiances intérieures où le confort thermique est recherché, mais où des écarts modérés dudit confort thermique se produisent, pour concevoir de nouvelles ambiances ou pour évaluer les ambiances existantes.
Spécifiquement développé pour les environnements de travail, le présent document peut cependant s’appliquer à d’autres types d’environnements.
Ergonomija toplotnega okolja - Analitično ugotavljanje in razlaga toplotnega ugodja z izračunom PMV in PPD vrednosti ter merili za lokalno toplotno ugodje (ISO 7730:2025)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN ISO 7730:2023
01-maj-2023
Nadomešča:
SIST EN ISO 7730:2006
Ergonomija toplotnega okolja - Analitično ugotavljanje in interpretacija toplotnega
ugodja z izračunom PMV in PPD vrednosti ter merili za lokalno toplotno ugodje
(ISO/DIS 7730:2023)
Ergonomics of the thermal environment - Analytical determination and interpretation of
thermal comfort using calculation of the PMV and PPD indices and local thermal comfort
criteria (ISO/DIS 7730:2023)
Ergonomie der thermischen Umgebung - Analytische Bestimmung und Interpretation der
thermischen Behaglichkeit durch Berechnung des PMV- und des PPD-Indexes und
Kriterien der lokalen thermischen Behaglichkeit (ISO/DIS 7730:2023)
Ergonomie des ambiances thermiques - Détermination analytique et interprétation du
confort thermique par le calcul des indices PMV et PPD et par des critères de confort
thermique local (ISO/DIS 7730:2023)
Ta slovenski standard je istoveten z: prEN ISO 7730
ICS:
13.180 Ergonomija Ergonomics
oSIST prEN ISO 7730:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
oSIST prEN ISO 7730:2023
oSIST prEN ISO 7730:2023
DRAFT INTERNATIONAL STANDARD
ISO/DIS 7730
ISO/TC 159/SC 5 Secretariat: BSI
Voting begins on: Voting terminates on:
2023-03-22 2023-06-14
Ergonomics of the thermal environment — Analytical
determination and interpretation of thermal comfort using
calculation of the PMV and PPD indices and local thermal
comfort criteria
Ergonomie des ambiances thermiques — Détermination analytique et interprétation du confort thermique
par le calcul des indices PMV et PPD et par des critères de confort thermique local
ICS: 13.180
This document is circulated as received from the committee secretariat.
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oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
DRAFT INTERNATIONAL STANDARD
ISO/DIS 7730
ISO/TC 159/SC 5 Secretariat: BSI
Voting begins on: Voting terminates on:
Ergonomics of the thermal environment — Analytical
determination and interpretation of thermal comfort using
calculation of the PMV and PPD indices and local thermal
comfort criteria
Ergonomie des ambiances thermiques — Détermination analytique et interprétation du confort thermique
par le calcul des indices PMV et PPD et par des critères de confort thermique local
ICS: 13.180
This document is circulated as received from the committee secretariat.
THIS DOCUMENT IS A DRAFT CIRCULATED
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ii
PROVIDE SUPPORTING DOCUMENTATION. © ISO 2023
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Whole body thermal comfort Predicted mean vote (PMV) . 2
4.1 Determination . 2
4.2 Applications. 4
5 Predicted percentage dissatisfied (PPD) . 4
6 Local thermal comfort . 5
6.1 General . 5
6.2 Draught . 6
6.3 Vertical air temperature difference . 6
6.4 Warm and cool floors . 7
6.5 Radiant temperature asymmetry . 8
7 Thermal environments for comfort . 9
8 Non-steady-state thermal environments .10
8.1 General . 10
8.2 Temperature cycles . 10
8.3 Temperature drifts or ramps . . 10
8.4 Transients . 10
Annex A (informative) Examples of thermal comfort requirements for different
categoriesof environment and types of space .11
Annex B (informative) Metabolic rates of different activities .16
Annex C (informative) Estimation of thermal insulation of clothing ensembles .17
Annex D (normative) Computer program for calculating PMV and PPD .21
Annex E (informative) Graphics for determination of predicted mean vote (PMV) .25
Annex F (informative) Humidity .28
Annex G (informative) Air velocity .29
Bibliography .31
iii
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International
Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies
casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 7730 was prepared by Technical Committee ISO/TC 159, Ergonomics, Subcommittee SC 5,
Ergonomics of the physical environment.
This fourth edition cancels and replaces the third edition (ISO 7730:2005), which has been technically
revised. Parts of the standard (long term evaluations, adaptation and diversity) has been moved to the
technical guideline DTRxxxxx. The mistakes in the calculation program has been corrected. The tables
for predicting PMV has been deleted, as most people today will use a calculation program.
iv
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
Introduction
This International Standard covering the evaluation of moderate thermal environments is one of a
series of ISO documents specifying methods for the measurement and evaluation of the moderate and
extreme thermal environments to which human beings are exposed (ISO 7243, ISO 7933 and ISO 11079,
all three dealing with extreme environmental conditions, are others in the series).
A human being's thermal sensation is mainly related to the thermal balance of his or her body as a
whole. This balance is influenced by physical activity and clothing, as well as the environmental
parameters: air temperature, mean radiant temperature, air velocity and air humidity. When these
factors have been estimated or measured, the index for thermal comfort, PMV (Predicted Mean Vote)
can be calculated. See Clause 4.
The predicted percentage dissatisfied (PPD) index provides information on thermal discomfort or
thermal dissatisfaction expressed as the percentage of people likely to feel too warm or too cool in a
given environment. The PPD can be obtained from the PMV. See Clause 5.
Thermal discomfort can also be caused by unwanted local cooling or heating of the body. The most
common local discomfort factors are radiant temperature asymmetry (cold or warm surfaces), draught
(defined as a local cooling of the body caused by air movement), vertical air temperature difference,
and cold or warm floors. Clause 6 specifies how to predict the percentage dissatisfied owing to local
discomfort parameters.
Dissatisfaction can be caused by hot or cold discomfort for the body as a whole. Comfort limits can in
this case be expressed by the PMV and PPD indices. But thermal dissatisfaction can also be caused by
local thermal discomfort parameters. Clause 7 deals with acceptable thermal environments for comfort.
Clauses 6 and 7 are based mainly on steady-state conditions. Means of evaluating non-steady-state
conditions such as transients (temperature steps), cycling temperatures or temperature ramps are
presented in Clause 8. The thermal environments in buildings or at workplaces will change over time
and it might not always be possible to keep conditions within recommended limits.
This standard is supposed to be used together with the technical guideline DTRxxxxx: Guidance for
design, control and evaluation of moderate indoor thermal environment
v
oSIST prEN ISO 7730:2023
oSIST prEN ISO 7730:2023
DRAFT INTERNATIONAL STANDARD ISO/DIS 7730:2023(E)
Ergonomics of the thermal environment — Analytical
determination and interpretation of thermal comfort using
calculation of the PMV and PPD indices and local thermal
comfort criteria
1 Scope
This International Standard defines a standardised method to evaluate the general thermal comfort of
people in a space and the degree of discomfort (thermal dissatisfaction) of people exposed to moderate
thermal environments. It defines the analytical determination and interpretation of thermal comfort
using calculation of PMV (predicted mean vote) and PPD (predicted percentage of dissatisfied) and
local thermal comfort criteria, giving the environmental conditions considered acceptable for general
thermal comfort as well as those representing local discomfort. It is applicable to healthy men and
women exposed to indoor environments where thermal comfort is desirable, but where moderate
deviations from thermal comfort occur, in the design of new environments or the assessment of
existing ones. Although developed specifically for the work environment, it is applicable to other kinds
of environment as well. It is intended to be used with reference to ISO 28803, when considering persons
with special requirements, such as those with physical disabilities. Ethnic, national or geographical
differences need also to be taken into account especially when considering non-conditioned spaces.
Guidance is given in clause 8 and 10 in the guideline ISO DTR XXXXX
2 Normative references
The following referenced documents are indispensable for the application 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 7726, Ergonomics of the thermal environment — Instruments for measuring physical quantities
ISO 8996, Ergonomics of the thermal environment — Determination of metabolic rate
ISO 9920, Ergonomics of the thermal environment — Estimation of thermal insulation and water vapour
resistance of a clothing ensemble
ISO 10551, Ergonomics of the physical environment — Subjective judgement scales for assessing physical
environments
ISO 13731, Ergonomics of the thermal environment — Vocabulary and symbols
ISO/TS 13732-2, Ergonomics of the thermal environment — Methods for the assessment of human responses
to contact with surfaces — Part 2: Human contact with surfaces at moderate temperature
ISO 28803, Ergonomics of the physical environment — Application of International Standards to people
with special requirements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13731 and the following apply.
3.1
temperature cycle
variable temperature with a given amplitude and frequency
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
3.2
drift temperature
passive monotonic, steady, non-cyclic change in the operative temperature of an enclosed space
3.3
ramp temperature
actively controlled monotonic, steady, non-cyclic change in the operative temperature of an enclosed
space
3.4
operative temperature
uniform temperature of an imaginary black enclosure in which an occupant would exchange the same
amount of heat by radiation and convection as in the actual non-uniform environment
3.5
transient temperature
sudden change in the thermal conditions due to step change in temperature, humidity, activity or
clothing
3.6
draught
unwanted local cooling of the body caused by air movement
4 Whole body thermal comfort Predicted mean vote (PMV)
4.1 Determination
The PMV is an index that predicts the mean value of the votes of a large group of persons on the 7-point
thermal sensation scale (see Table 1), based on the heat balance of the human body. Thermal balance is
obtained when the internal heat production in the body is equal to the loss of heat to the environment.
In a moderate environment, the human thermoregulatory system will automatically attempt to modify
skin temperature and sweat secretion to maintain heat balance.
Table 1 — Seven-point thermal sensation scale
+ 3 Hot
+ 2 Warm
+ 1 Slightly warm
0 Neutral
− 1 Slightly cool
−2 Cool
− 3 Cold
Calculate the PMV using Equations (1) to (4):
PMVM=−[,0 303··exp( 0,)036 +0,]028 .
−3
()MW− −⋅3,05 105⋅−[]733 69,,90⋅−()MW −pM−⋅42 []()−W −58,15
a
−5
−1,771⋅⋅05Mp⋅−867 −⋅0,00143Mt⋅−4 (1)
() ()
aa
−8
−⋅39, 610 ⋅⋅ft(()+273 −+()tf273 −⋅ht⋅−()t
cl cl rclc cl a
4 44
−8
tM=−35,70,028⋅−WI−⋅ 39, 61⋅⋅0 ft⋅+273 −+t 273 +⋅fh ⋅−tt (2)
() () () ()
{}
cl cl cl cl r cl ccla
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
02,,50 25
23,,81⋅−tt for 2,38⋅−tt >⋅21 v
cl acla ar
h = (3)
c
02, 5
12,1⋅ v for 22,38⋅−tt <⋅12,1 v
ar cl aar
10,,01+⋅290llformu0,078 K/W
cl cl
f = (4)
cl
10,,50+>645llfor 00, 778mK⋅ /W
cl cl
where
M is the metabolic rate, in watts per square metre (W/m );
W is the effective mechanical power, in watts per square metre (W/m );
I is the clothing insulation, in square metres kelvin per watt (m ⋅ K/W);
cl
f is the clothing surface area factor;
cl
t is the air temperature, in degrees Celsius (°C);
a
t
is the mean radiant temperature, in degrees Celsius (°C);
r
v is the relative air velocity, in metres per second (m/s);
ar
p is the water vapour partial pressure, in pascals (Pa);
a
h is the convective heat transfer coefficient, in watts per square metre kelvin [W/(m ⋅ K)];
c
t is the clothing surface temperature, in degrees Celsius (°C).
cl
2 2
NOTE 1 metabolic unit = 1 met = 58,2 W/m ; 1 clothing unit = 1 clo = 0,155 m ⋅ °C/W.
PMV may be calculated for different combinations of metabolic rate, clothing insulation, air temperature,
mean radiant temperature, air velocity and air humidity (see ISO 7726). The equations for t and h
cl c
may be solved by iteration.
The PMV index is derived for steady-state conditions but can be applied with good approximation
during minor fluctuations of one or more of the variables, provided that time-weighted averages of the
variables during the previous 1 h period are applied.
The index should be used only for values of PMV between −2 and +2, and when the six main parameters
are within the following intervals:
2 2
M 46 W/m to 232 W/m (0,8 met to 4 met);
2 2
I 0 m ⋅ K/W to 0,310 m ⋅ K/W (0 clo to 2 clo);
cl
t 10 °C to 30 °C;
a
t
10 °C to 40 °C;
r
v 0 m/s to 1 m/s;
ar
p 0 Pa to 2 700 Pa.
a
NOTE In respect of v , during light, mainly sedentary, activity, a mean velocity within this range can be felt
ar
as a draught.
Estimate the metabolic rate using ISO 8996 or Annex B, taking into account the type of work. For
varying metabolic rates, a time-weighted average should be estimated during the previous 1 h period.
Estimate the thermal resistance of clothing and chair using ISO 9920 or Annex C, taking into account
the time of year.
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
Determine the PMV in one of the following ways.
a) From Equation (1) using a digital computer. A BASIC program is given in Annex D for this purpose.
For verification of other computer programs, Annex D provides example output.
b) From Annex E, where graphics of PMV values are given for different combinations of activity,
clothing, operative temperature and relative velocity.
c) By direct measurement, using an integrating sensor (equivalent and operative temperatures).
The influence of humidity on thermal sensation is small at moderate temperatures close to comfort and
may usually be disregarded when determining the PMV value (see Annex F).
4.2 Applications
The PMV can be used to check whether a given thermal environment complies with comfort criteria
(see Clause 7 and Annex A), and to establish requirements for different categories of acceptability.
By setting PMV = 0, an equation is established which predicts combinations of activity, clothing and
environmental parameters which on average will provide a thermally neutral sensation.
5 Predicted percentage dissatisfied (PPD)
The PMV-index is defined in relation to the mean value of the thermal votes of a large group of people
exposed to the same environment. But individual votes are scattered around this mean value and it is
useful to be able to predict the number of people likely to feel uncomfortably warm or cool.
The PPD is an index that establishes a quantitative index related to the percentage of thermally
dissatisfied people who feel too cool or too warm. For the purposes of this International Standard,
thermally dissatisfied people are those who will vote hot, warm, cool or cold on the 7-point thermal
sensation scale given in Table 1.
With the PMV value determined, calculate the PPD using Equation (5), see Figure 1:
PPD=−100 95⋅−exp( 0,,03353⋅−PMVP0 2179⋅ MV ) (5)
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
Key
PMV predicted mean vote
PPD predicted percentage dissatisfied, %
Figure 1 — PPD as function of PMV
The PPD is related to the number of thermally dissatisfied persons among a large group of people. The
rest of the group will feel thermally neutral, slightly warm or slightly cool. The relation between PMV
and PPD distributionis given in Table 2.
Table 2 — Distribution of individual thermal sensation votes for different values of mean vote
a
PMV PPD Persons predicted to vote
%
0 −1, 0 or +1 −2, −1, 0, +1 or +2
+2 75 5 25 70
+1 25 30 75 95
+0,5 10 55 90 98
0 5 60 95 100
−0,5 10 55 90 98
−1 25 30 75 95
−2 75 5 25 70
a
Based on experiments involving 1 300 subjects.
6 Local thermal comfort
6.1 General
The PMV and PPD are indices related to warm and cold discomfort for the body as a whole. But thermal
dissatisfaction can also be caused by unwanted cold or warm sensation of a particular part of the body.
This is known as local discomfort. The most common cause of local discomfort is draught (6.2). But local
discomfort can also be caused by an abnormally high vertical temperature difference between the head
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
and ankles (6.3), by too warm or too cool a floor (6.4), or by a radiant temperature asymmetry (6.5).
Annex A provides examples of local and overall thermal comfort requirements for different categories
of environment and types of space.
It is mainly people at light sedentary activity who are sensitive to local discomfort. These will have
a thermal sensation for the whole body close to neutral. At higher levels of activity, people are less
thermally sensitive and consequently the risk of local discomfort is lower.
6.2 Draught
The discomfort due to draught may be expressed as the percentage of people predicted to be bothered
by draught. Calculate the draught rate (DR) using Equation (6) (model of draught):
06, 2
DR=−34 tv −00,,50 37⋅⋅vTu+31, 4 (6)
()
()a,la(),l
a,l
For v < 0,05 m/s: use v = 0,05 m/s
a,l a,l
For DR > 100 %: use DR = 100 %
where
t is the local air temperature, in degrees Celsius, 20 °C to 26 °C;
a,l
v
is the local mean air velocity, in metres per second, < 0,5 m/s;
a,l
Tu is the local turbulence intensity, in percent, 10 % to 60 % (if unknown, 40 % may be used).
The model applies to people at light, mainly sedentary activity with a thermal sensation for the whole
body close to neutral and for prediction of draught at the neck. At the level of arms and feet, the model
could overestimate the predicted draught rate. The sensation of draught is lower at activities higher
than sedentary (> 1,2 met) and for people feeling warmer than neutral. Additional information on the
effect of air velocity can be found in Annex G.
6.3 Vertical air temperature difference
A high vertical air temperature difference between head and ankles can cause discomfort. Figure 2
shows the percentage dissatisfied (PD) as a function of the vertical air temperature difference between
head and ankles. The figure applies when the temperature increases upwards. People are less sensitive
under decreasing temperatures. Determine the PD using Equation (7):
PD= (7)
15+−exp( ,,76 0 856⋅Δt )
a,v
Equation (7), derived from the original data using logistic regression analysis, should only be used at
Δt < 8 °C.
a,v
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
Key
PD percentage dissatisfied, %
Δt vertical air temperature difference between head and feet, °C
a,v
Figure 2 — Local discomfort caused by vertical air temperature difference
6.4 Warm and cool floors
If the floor is too warm or too cool, the occupants could feel uncomfortable owing to thermal sensation
of their feet. For people wearing light indoor shoes, it is the temperature of the floor rather than the
material of the floor covering which is important for comfort. Figure 3 shows the percentage dissatisfied
as a function of the floor temperature, based on studies with standing and/or sedentary people.
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
Key
PD percentage dissatisfied, %
t floor temperature, °C
f
Figure 3 — Local thermal discomfort caused by warm or cold floors
For people sitting or lying on the floor, similar values may be used. Determine the PD using Equation (8),
derived from the original data using non-linear regression analysis:
PD=−100 94⋅−exp( 1,,387+⋅0 118 tt−⋅0,)0025 (8)
ff
For longer occupancy the results are not valid for electrically heated floors.
NOTE By electrical heating, a certain heat input is provided independent of the surface temperature. A
water-based heating system will not produce temperatures higher than the water temperature.
For spaces that people occupy with bare feet, see ISO/TS 13732-2.
6.5 Radiant temperature asymmetry
Radiant temperature asymmetry (Δt ) can also cause discomfort. People are most sensitive to
pr
radiant asymmetry caused by warm ceilings or cool walls (windows). Figure 4 shows the percentage
dissatisfied as a function of the radiant temperature asymmetry caused by a warm ceiling, a cool wall,
a cool ceiling or by a warm wall. For horizontal radiant asymmetry, Figure 4 applies from side-to-side
(left/right or right/left) asymmetry, the curves providing a conservative estimate of the discomfort:
no other positions of the body in relation to the surfaces (e.g. front/back) cause higher asymmetry
discomfort. Determine the PD using Equations (9) to as applicable.
PD = 100/(1+exp(K1-K2*Δt ))-K3 (9)
pr
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
Table 3 — Constants to be used in equation (9) for different types of radiant assymmetry.
Asymmetri Δt limit K1 K2 K3
pr
1-Warm Ceiling < 23 K 2,94 0,166 5,5
2 Cool Wall < 15 K 5,89 0,297 0
3 Cool Ceiling < 15 K 5,19 0,173 0
4-Warm Wall < 35 K 3,41 0,044 3,5
Equations (9) were derived from the original data using logistic regression analysis, and should not be
used beyond the ranges shown above. Those for a) (warm ceiling) and for d) (warm wall) have been
adjusted to account for discomfort not caused by radiant asymmetry. See Figure 4.
Key
PD percentage dissatisfied, %
Δt radiant temperature asymmetry, °C
pr
1 warm ceiling
2 cool wall
3 cool ceiling
4 warm wall
Figure 4 — Local thermal discomfort caused by radiant temperature asymmetry
7 Thermal environments for comfort
Thermal comfort is that condition of mind which expresses satisfaction with the thermal environment.
Dissatisfaction can be caused by warm or cool discomfort of the body as a whole, as expressed by the
PMV and PPD, or by a warm or cold sensation of one particular part of the body (local comfort).
Due to individual differences, it is impossible to specify a thermal environment that will satisfy
everybody. There will always be a percentage dissatisfied occupants.
Often it will be the same persons who are sensitive to different types of local discomfort. For instance,
a person sensitive to draught may also be sensitive to local cooling caused by radiant asymmetry or by
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
a cold floor. Such a cold-sensitive person may also more easily experience cool discomfort for the body
as a whole. Therefore, the PPD, DR or PD caused by other types of local discomfort should not be added.
Due to local or national priorities, technical developments and climatic regions, a higher thermal quality
(fewer dissatisfied) or lower quality (more dissatisfied) in some cases may be accepted. In such cases,
the PMV and PPD, the model of draught, the relation between local thermal discomfort parameters (see
Clause 6), and the expected percentage of dissatisfied people may be used to determine different ranges
of environmental parameters for the evaluation and design of the thermal environment.
Examples of different categories of requirements are given in Annex A.
8 Non-steady-state thermal environments
8.1 General
The basis for the methods given in the preceding clauses is steady-state conditions. The thermal
environment is, however, often in a non-steady-state and the question arises as to whether the methods
then apply. Three types of non-steady-state conditions can occur: temperature cycles, temperature
drifts or ramps, and transients.
8.2 Temperature cycles
Temperature cycles can occur due to the control of the temperature in a space. If the peak-to-peak
variation is less than 1 K, there will be no influence on the comfort and the recommendations for
steady-state may be used. Higher peak variations can decrease comfort.
8.3 Temperature drifts or ramps
If the rate of temperature change for drifts or ramps is lower than 4,0 K/h, the methods for steady-state
variation apply.
8.4 Transients
In general, the following statements regarding transients can be made.
— A step-change of operative temperature is felt instantaneously.
— After an up-step in operative temperature, the new steady-state thermal sensation is experienced
immediately, i.e. the PMV-PPD indices can be used.
— Following a down-step in operative temperature, the thermal sensation drops at first to a level
beneath the PMV-index, then increases and reaches under steady-state conditions the steady-state
level after approximately 30 min, i.e. the PMV-PPD index show values that are too high for the first
30 min. The time to reach a new steady-state condition depends on the initial conditions.
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
Annex A
(informative)
Examples of thermal comfort requirements for different
categoriesof environment and types of space
A.1 Categories of thermal environment
The desired thermal environment for a space may be selected from among the four categories, I, II, III
and IV according to Table A.1. For local discomfort only three categories apply. All the criteria should be
satisfied simultaneously for each category.
Table A.1 — Categories of thermal environment
Thermal state of the body as a whole Local discomfort
PPD PMV DR PD
% % %
Category
vertical air caused by radiant asym-
temperature warm or cool metry
difference floor
I < 6 − 0,2 < PMV < + 0,2 < 10 < 3 < 10 < 5
II < 10 − 0,5 < PMV < + 0,5 < 20 < 5 < 10 < 5
III < 15 − 0,7 < PMV < + 0,7 < 30 < 10 < 15 < 10
IV < 25 − 1,0 < PMV < + 1,0
Each category prescribes a maximum percentage dissatisfied for the body as a whole (PPD) and a PD
for each of the four types of local discomfort. Some requirements are difficult to meet in practice while
others are quite easily met. The different percentages express a balance struck between the aim of a
few dissatisfied and what is practically obtainable using existing technology.
Owing to the accuracy of instrumentation for measuring the input parameters according to ISO 7726,
it can be difficult to verify that the PMV conforms to the Class A category (−0,2 < PMV < +0,2). Instead,
the verification may be based on the equivalent operative temperature range, as specified in A.2 and in
Table A.5.
The four categories presented in Table A.1 apply to spaces where persons are exposed to the same
thermal environment. It is an advantage if some kind of individual control of the thermal environment
can be established for each person in a space. Individual control of the local air temperature, mean
radiant temperature or air velocity can contribute to balancing the rather large differences between
individual requirements and consequently can lead to fewer dissatisfied.
Modification of the clothing can also contribute to balance individual differences. The effect on the
optimum operative temperature of adding or removing different garments is described in Table C.2.
A.2 Operative temperature range
For a given space there exists an optimum operative temperature corresponding to PMV = 0,
depending on the activity and the clothing of the occupants. Figure A.1 shows the optimum operative
temperature and the permissible temperature range as a function of clothing and activity for three of
the four categories. The optimum operative temperature is the same for the three categories, while the
permissible range around the optimum operative temperature varies.
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
The operative temperature at all locations within the occupied zone of a space should at all times be
within the permissible range. This means that the permissible range should cover both spatial and
temporal variations, including fluctuations caused by the control system.
Figure A.1 applies for a relative humidity of 50 %; however, in moderate environments the air humidity
has only a modest impact on the thermal sensation. Typically, a 10 % higher relative humidity and a
0,3 °C higher operative temperature are perceived as being warmer in equal measure.
The PDs in Table A.1 are not additive. In practice, a higher or lower number of dissatisfied persons may
be found when using subjective questionnaires in field investigations (see ISO 10551).
The air velocity in the space is assumed to be < 0,1 m/s. The relative air velocity, v , caused by body
ar
movement is estimated to be zero for a metabolic rate, M, less than 1 met and v = 0,3 (M − 1) for M > 1
ar
met. The diagrams are determined for a relative humidity = 50 %, but the humidity only has a slight
influence on the optimum and permissible temperature ranges.
A.3 Local thermal comfort
Figure A.2 give ranges for local thermal comfort due to draught for the three categories presented in
Table A.1.
The max. allowable mean air velocity is a function of local air temperature and turbulence intensity.
The turbulence intensity may vary between 30 % and 60 % in spaces with mixed-flow air distribution.
In spaces with displacement ventilation or without mechanical ventilation, the turbulence intensity
may be lower.
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
The diagrams also show the range around the optimum temperature for the three categories.
Key
X basic clothing insulation, in clothing units, (clo)
X′ basic clothing insulation, in clothing units, m ⋅°C/W
Y metabolic rate, in metabolic units, (met)
Y′ metabolic rate, in metabolic units, W/m
PPD predicted percentage dissatisfied, %
Figure A.1 — Optimum operative temperature as function of clothing and activity
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
Key
t local air temperature, °C
a,l
local mean air velocity, m/s
v
a,l
Tu turbulence intensity, %
Figure A.2 — Max. allowable mean air velocity as function of local air temperature
and turbulence intensity
Tables A.2, A.3 and A.4 give values for-local thermal comfort related to: vertical air temperature
difference, warm/cold floor and radiant temperature asymmetry.
Table A.2 — Vertical air temperature difference between head and ankles
a
Category Vertical air temperature difference
°C
I < 2
II < 3
III < 4
a
1,1 and 0,1 m above floor.
Table A.3 — Range of floor temperature
Category Floor surface temperature range
°C
I 19 to 29
II 19 to 29
III 17 to 31
Table A.4 — Radiant temperature asymmetry
Category Radiant temperature asymmetry
°C
Warm ceiling Cool wall Cool ceiling Warm wall
I < 5 < 10 < 14 < 23
II < 5 < 10 < 14 < 23
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
TTabablele A A.44 ((ccoonnttiinnueuedd))
Category Radiant temperature asymmetry
°C
Warm ceiling Cool wall Cool ceiling Warm wall
III < 7 < 13 < 18 < 35
A.4 Design criteria for different types of space — Examples
The design criteria specified in Table A.5 are derived under certain assumptions. For the thermal
environment, the criteria for the operative temperature are based on typical levels of activity, for
clothing of 0,5 clo during summer (“cooling season”) and 1,0 clo during winter (“heating season”).
The criteria for the mean air velocity apply for a turbulence intensity of approximately 40 % (mixing
ventilation). The design criteria are valid for the occupancy conditions as given, but could also be
applicable to other types of spaces used in similar ways.
Table A.5 — Example design criteria for spaces in various types of building
a
Type of building/ Activity Category Operative temperature Maximum mean air velocity
space met °C m/s
Summer Winter Summer Winter
W/m
(cooling sea- (heating sea- (cooling sea- (heating sea-
son) son) son) son)
Single office
I 24,5 ± 1,0 22,0 ± 1,0 0,12 0,10
1,2 met
Landscape office
II 24,5 ± 1,5 22,0 ± 2,0 0,19 0,16
Conference room
b
III 24,5 ± 2,5 22,0 ± 3,0 0,24 0,21
Auditorium
70 W/m
Cafeteria/restaurant
IV 24,5 ± 3,5 22,0 ± 4,0
Classroom
b
Kindergarten I 23,5 ± 1,5 20,5 ± 2,0 0,11 0,10
b
1,4 met II 23,5 ± 2,0 20,5 ± 3,0 0,18 0,15
Standing/Sedentary
b
81 W/m III 23,5 ± 3,0 20,5 ± 4,0 0,23 0,19
IV 23,5 ± 4,0 20,5 ± 5,0
b
Department store I 23,0 ± 1,5 20,0 ± 2,0 0,16 0,13
b
1,6 met
II 23,0 ± 2,0 20,0 ± 3,0 0,20 0,15
Standing/walking
2 b
III 23,0 ± 3,0 20,0 ± 4,0 0,23 0,18
93 W/m
IV 23,0 ± 4,0 20,0 ± 5,0
a
The maximum mean air velocity is based on a turbulence intensity of 40 % and air temperature equal to the operative
temperature according to 6.2 and Figure A.2. A relative humidity of 60 % and 40 % is used for summer and winter,
respectively. For both summer and winter a lower temperature in the range is used to determine the maximum mean air
velocity.
b
Below 20 °C limit (see Figure A.2).
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
Annex B
(informative)
Metabolic rates of different activities
Further information on metabolic rates is given in ISO 8996. That elderly people often have a lower
average activity than younger people also needs to be taken into account.
Table B.1 — Examples of Metabolic rates
Activity Metabolic rate
W/m met
Reclining 46 0,8
Seated, relaxed 58 1,0
Sedentary activity (office, dwelling, school, laboratory) 70 1,2
Standing, light activity (shopping, laboratory, light industry) 93 1,6
Standing, medium activity (shop assistant, domestic work, machine
116 2,0
work)
Walking on level ground:
2 km/h 110 1,9
3 km/h 140 2,4
4 km/h 165 2,8
5 km/h 200 3,4
oSIST prEN ISO 7730:2023
ISO/DIS 7730:2023(E)
Annex C
(informative)
Estimation of thermal insulation of clothing ensembles
C.1 General
The clothing insulation (I ) can be estimated directly from the data presented in Table C.1 for typical
cl
combinations of garments (the values are for static thermal insulation), or indirectly, by summation of
the partial insulation values for each item of clothing, I , as presented in Table C.2.
clu
Table C.2 gives the corresponding change in the optimum operative temperature necessary to maintain
thermal sensation at neutral when a garment is added or removed at light mainly sedentary activity
(1,2 met).
For sedentary persons, the chair can contribute an additional insulation of 0 clo to 0,4 clo (see Table C.3).
Further information is given in ISO 9920.
Table C.1 — Thermal insulation for typical combinations of garments
Work clothing I Daily wear clothing I
cl cl
2 2
clo m ⋅ K/W clo m ⋅ K/W
Underpants, boiler suit, socks, Panties, T-shirt, shorts, light socks,
0,70 0,110 0,30 0,050
shoes sandals
Underpants, shirt with short
Underpants, shirt, boiler suit,
0,80 0,125 sleeves, light trousers, light socks, 0,50 0,080
socks, shoes
shoes
Underpants, shirt, trousers, smock, Panties, petticoat, stockings, dress,
0,90 0,140 0,70 0,105
socks, shoes shoes
Underwear with short sleeves and
Underwear, shirt, trousers, socks,
legs, shirt, trousers, jacket, socks, 1,00 0,155 0,70 0,110
shoes
shoes
...
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