EN ISO 9288:2022

Thermal insulation - Heat transfer by radiation - Vocabulary (ISO 9288:2022)

This document defines physical quantities and other terms in the field of thermal insulation relating to heat transfer by radiation.

Wärmeschutz - Wärmeübertragung durch Strahlung - Physikalische Größen und Definitionen (ISO 9288:2022)

Dieses Dokument legt physikalische Größen und andere Begriffe fest, die sich auf den Bereich des Wärmeschutzes in Zusammenhang mit Wärmeübertragung durch Strahlung beziehen.

Isolation thermique - Transfert de chaleur par rayonnement - Vocabulaire (ISO 9288:2022)

Le présent document définit des grandeurs physiques et d’autres termes du domaine de l’isolation thermique liés au transfert de chaleur par rayonnement.

Toplotna izolacija - Prenos toplote s sevanjem - Slovar (ISO 9288:2022)

Ta dokument določa fizikalne veličine in druge izraze na področju toplotne izolacije v zvezi s prenosom toplote s sevanjem.

General Information

• Status: Published
• Publication Date: 13-Sep-2022
• ICS: 01.060 - Quantities and units
• ICS: 27.220 - Heat recovery. Thermal insulation
• Technical Committee: CEN/TC 89 - Thermal performance of buildings and building components
• Drafting Committee: CEN/TC 89 - Thermal performance of buildings and building components
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 14-Sep-2022
• Completion Date: 14-Sep-2022
• Ref Project: SIST EN ISO 9288:2022 - Thermal insulation - Heat transfer by radiation - Vocabulary (ISO 9288:2022)

Relations

• Replaces: EN ISO 9288:1996 - Thermal insulation - Heat transfer by radiation - Physical quantities and definitions (ISO 9288:1989)
• Effective Date: 21-Sep-2022

Overview

EN ISO 9288:2022 - Thermal insulation - Heat transfer by radiation - Vocabulary (ISO 9288:2022) is a terminology standard that defines the physical quantities and terms used in the field of thermal insulation when describing heat transfer by radiation. Prepared by ISO/TC 163 and adopted by CEN, this vocabulary standard replaces the earlier edition and provides a common, authoritative language for radiative heat-transfer concepts used in building physics, materials testing and thermal design.

Key topics

The standard covers concise, technical definitions and relationships for concepts including:

• Thermal radiation and heat transfer by radiation (scope and spectral relevance)
• Spectral versus total quantities: spectral radiation, spectral radiance, spectral intensity, spectral radiant heat flow rate
• Directional and hemispherical descriptions: directional radiation, hemispherical radiation, radiance, intensity
• Surface and medium classifications: opaque medium vs semi‑transparent medium and their radiative behaviors
• Radiative flux and density measures: radiant heat flow rate (Φ), radiant density of heat flow rate (q), including forward and backward components
• Combined conduction and radiation concepts for semi‑transparent materials and experimental determination methods (e.g., guarded hot plate, heat flow meter)

Practical applications

EN ISO 9288:2022 is a foundational reference for professionals who need consistent terminology when working with radiative heat transfer in thermal insulation contexts. Typical uses include:

• Writing and interpreting test methods and lab reports for insulation materials (manufacturers, test laboratories)
• Developing or applying building thermal-performance models where radiative exchanges are important (building physicists, energy modelers)
• Specifying or assessing radiative properties of surfaces and semi‑transparent materials in HVAC, façade and glazing design (engineers, architects)
• Harmonizing standards and regulatory documents where precise radiative terms avoid ambiguity (standards bodies, regulators)

By standardizing definitions such as radiance, spectral radiance and semi‑transparent medium, EN ISO 9288:2022 improves clarity across testing, simulation and specification workflows.

Related standards

EN ISO 9288:2022 is intended to be used alongside other thermal insulation vocabularies and methods, for example:

• ISO 7345
• ISO 9229
• ISO 9251
• ISO 9346

For authoritative implementation in Europe, the ISO text has been endorsed as EN ISO 9288:2022 by CEN and is to be adopted as a national standard by CEN member bodies.

Standards Content (Sample)

SLOVENSKI STANDARD
01-november-2022
Nadomešča:
SIST EN ISO 9288:1997
Toplotna izolacija - Prenos toplote s sevanjem - Slovar (ISO 9288:2022)
Thermal insulation - Heat transfer by radiation - Vocabulary (ISO 9288:2022)
Wärmeschutz - Wärmeübertragung durch Strahlung - Physikalische Größen und
Definitionen (ISO 9288:2022)
Isolation thermique - Transfert de chaleur par rayonnement - Vocabulaire (ISO
9288:2022)
Ta slovenski standard je istoveten z: EN ISO 9288:2022
ICS:
01.060 Veličine in enote Quantities and units
27.220 Rekuperacija toplote. Heat recovery. Thermal
Toplotna izolacija insulation
91.120.10 Toplotna izolacija stavb Thermal insulation of
buildings
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 9288
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2022
EUROPÄISCHE NORM
ICS 01.060; 27.220 Supersedes EN ISO 9288:1996
English Version
Thermal insulation - Heat transfer by radiation -
Vocabulary (ISO 9288:2022)
Isolation thermique - Transfert de chaleur par Wärmeschutz - Wärmeübertragung durch Strahlung -
rayonnement - Vocabulaire (ISO 9288:2022) Physikalische Größen und Definitionen (ISO
9288:2022)
This European Standard was approved by CEN on 28 July 2022.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 9288:2022 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 9288:2022) has been prepared by Technical Committee ISO/TC 163 "Thermal
performance and energy use in the built environment" in collaboration with Technical Committee
CEN/TC 89 “Thermal performance of buildings and building components” the secretariat of which is
held by SIS.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by March 2023, and conflicting national standards shall
be withdrawn at the latest by March 2023.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 9288:1996.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 9288:2022 has been approved by CEN as EN ISO 9288:2022 without any modification.

INTERNATIONAL ISO
STANDARD 9288
Second edition
2022-08
Thermal insulation — Heat transfer by
radiation — Vocabulary
Isolation thermique — Transfert de chaleur par rayonnement —
Vocabulaire
Reference number
ISO 9288:2022(E)
ISO 9288:2022(E)
© ISO 2022
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: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 9288:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions (General terms) . 1
4 Terms related to surfaces either receiving, transferring or emitting a thermal
radiation . 3
5 Terms related to surfaces emitting a thermal radiation . 7
6 Terms related to opaque or semi-transparent surfaces receiving a thermal
radiation .10
7 Terms related to a semi-transparent medium receiving a thermal radiation —
Combined conduction and radiation heat transfer .14
Bibliography .21
Index .22
iii
ISO 9288:2022(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.
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).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
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 163, Thermal performance and energy
use in the built environment, in collaboration with the European Committee for Standardization
(CEN) Technical Committee CEN/TC 89, Thermal performance of buildings and building components, in
accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 9288:1989), which has been technically
revised.
The main changes are as follows:
— deleted the unit where two units existed (4.5, 4.6, 4.8, 4.9, 4.10, 5.3, 5.6, 6.2, 6.4);
— added the mean of d and d (7.15);
∞
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 9288:2022(E)
Introduction
This document is intended to be used in conjunction with other vocabularies related to thermal
insulation. These include:
— ISO 7345
— ISO 9229
— ISO 9251
— ISO 9346
v
INTERNATIONAL STANDARD ISO 9288:2022(E)
Thermal insulation — Heat transfer by radiation —
Vocabulary
1 Scope
This document defines physical quantities and other terms in the field of thermal insulation relating to
heat transfer by radiation.
2 Normative references
There are no normative references in this document.
3 Terms and definitions (General terms)
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
thermal radiation
electromagnetic radiation emitted at the surface of an opaque body or inside an element of a semi-
transparent volume
Note 1 to entry: The thermal radiation is governed by the temperature of the emitting body and its radiative
characteristics. It is interesting from a thermal viewpoint when the wavelength range falls between 0, l μm and
100 μm (see Figure 1).
ISO 9288:2022(E)
Key
1 solar radiation
2 thermal radiation
3 infrared
4 visible
5 ultraviolet
6 wavelength μm
-1
7 frequency s
Figure 1 — Electromagnetic wave spectrum
3.2
heat transfer by radiation
energy exchanged between bodies by means of electromagnetic waves
Note 1 to entry: These exchanges can occur when the bodies are separated from one another by vacuum or by a
transparent or a semi-transparent medium. To evaluate these radiation heat exchanges it is necessary to know
how opaque and semi-transparent bodies emit, absorb and transmit radiation as a function of their nature,
relative position and temperature.
3.3
total radiation
entire spectrum of thermal radiation
3.4
spectral radiation
monochromatic radiation
spectral interval centred on the wavelength λ of thermal radiation, according to spectral distribution
3.5
hemispherical radiation
all directions of thermal radiation along which a surface element can emit or receive radiation,
according to spatial distribution (directional)
ISO 9288:2022(E)
3.6
directional radiation
thermal radiation whose directions of propagation are defined by a solid angle around the defined
direction, according to spatial distribution
3.7
opaque medium
medium, which does not transmit any fraction of the incident radiation
Note 1 to entry: The absorption, emission (5.1) and reflection of radiation can be handled as surface phenomena
3.8
semi-transparent medium
medium, in which the incident radiation is progressively attenuated inside the material by absorption
or scattering, or both
Note 1 to entry: The absorption, scattering and emission (5.1) of radiation are bulk (volume) phenomena.
Note 2 to entry: The radiative properties of an opaque or semi-transparent medium are generally a function of
the spectral and directional distribution of incident radiation and of the temperature of the medium.
Note 3 to entry: Thermal insulating materials are generally semi-transparent media.
4 Terms related to surfaces either receiving, transferring or emitting a thermal
radiation
4.1
radiant heat flow rate
radiant flux
Φ
heat flow rate emitted, transferred or received by a system in form of electromagnetic waves
Note 1 to entry: This is a total hemispherical quantity. See Table 1.
Note 2 to entry: Expressed in W.
4.2
total intensity
I
Ω

radiant heat flow rate (4.1) divided by the solid angle around the direction Δ :
dφ
I =
Ω
dΩ
Note 1 to entry: Expressed in W/sr.
4.3
total radiance
L
Ω

radiant heat flow rate (4.1) divided by the solid angle around the direction Δ and the projected area
normal to this direction:
d Φ
L =
Ω
ddΩ ()Acosθ
Note 1 to entry: Expressed in Wm/ ⋅sr .
()
ISO 9288:2022(E)
4.4
spectral radiant heat flow rate
Φ
λ
radiant heat flow rate (4.1) divided by the spectral interval centred on the wavelength λ :
dφ
φ =
λ
dλ
Note 1 to entry: Expressed in W/m.
4.5
spectral intensity
I
Ωλ
total intensity (4.2) divided by the spectral interval centred on the wavelength λ :
dI
Ω
I =
Ωλ
dλ
Note 1 to entry: Expressed in Ws/ rm⋅ .
()
4.6
spectral radiance
L
Ωλ
total radiance (4.3) divided by the spectral interval centred on the wavelength λ :
dL
Ω
L =
Ωλ
dλ
Note 1 to entry: Expressed in Wm/ ⋅sr .
()
Note 2 to entry: Each spectral term A is related to the corresponding total term A by a relation of the type
λ
∞
dA
A == or AA dλ
λλ
∫
dλ
Note 3 to entry: Each directional term A is related to the corresponding hemispherical term A by a relation of
Ω
the type
dA
A == or AA dΩ
ΩΩ
∫
Ω=4π
dΩ
and
∞
dA
A == or AA dλΩd
Ωλ Ωλ
∫ ∫
Ω=4π 0
ddΩ λ
Note 4 to entry: Total radiance and spectral radiance are oriented quantities (vectors) defined in each point of
space where radiation exists (see Figure 3), moreover their values are independent of the particular surface used
to define them. Sources which radiate with constant L (see 4.3) are called isotropic or diffuse.
Ω
Note 5 to entry: Intensities are oriented quantities too, but belong to a surface (see Figure 2).
Note 6 to entry: Radiant flows (total or spectral) are not oriented quantities and belong to a surface.
ISO 9288:2022(E)
Figure 2 — Definition of the intensity
Figure 3 — Definition of the radiance
4.7
spectral radiant density of heat flow rate vector

q
r,λ


qL= ΔΩd
r,λ Ωλ
∫
Ω=4π
where
L
is the spectral radiance (4.6);
Ωλ
ISO 9288:2022(E)

is the solid angle around the direction.
Δ
Note 1 to entry: Expressed in Wm/ .
4.8
total radiant density of heat flow rate vector

q
r

∞ 
qL= ΔΩd dλ
r Ωλ
∫ ∫
0 Ω=4π
where
L
is the spectral radiance (4.6);
Ωλ

is the solid angle around the direction;
Δ
λ is the wavelength.
Note 1 to entry: Expressed in W/m .
4.9
spectral radiant density of heat flow rate
q
rn,λ


 
qn=⋅qL=⋅ΔΩnd
rn,,λλr Ωλ
∫
Ω=4π
where
L
is the spectral radiance (4.6);
Ωλ

is the solid angle around the direction;
Δ

n is the heat flow rate in the direction.
Note 1 to entry: Expressed in Wm/ .

Note 2 to entry: Heat flow rate in the direction n .
4.10
forward component of the spectral radiant density of heat flow rate
+
q
rn,λ


 
+
qn=⋅qL=⋅ΔΩnd
rn,,λλr ∫ Ωλ
Ω=2π
where
L
is the spectral radiance (4.6);
Ωλ

is the solid angle around the direction;
Δ

n is the heat flow rate in the direction.
Note 1 to entry: Expressed in Wm/ .
ISO 9288:2022(E)
4.11
backward component of the spectral radiant density of heat flow rate
−
q
rn,λ


 
−
qn=⋅qL=− Δ⋅ndΩ
rn,,λλr Ωλ
∫
Ω=2π
where
L
is the spectral radiance (4.6);
Ωλ

is the solid angle around the direction;
Δ

n is the heat flow rate in the direction.
Note 1 to entry: Expressed in Wm/ .
()
Note 2 to entry: q is expressed by the following:
r ,λ
n
+−
qq=−q
r,λ r,λ
r,λ
n n
n

in combined unidirectional conduction and radiation heat transfer along a direction n , gives
 
qq=+q
ncdn,,rn
where

is the density of heat flow rate as defined in ISO 7345;
q
n

is the density of heat flow rate by conduction;
q
cd,n

is the total radiant density of heat flow rate vector (4.8);
q
rn,

can be determined experimentally with the guarded hot plate or heat flow meter method.
q
n
5 Terms related to surfaces emitting a thermal radiation
5.1
emission
process in which heat is transformed into electromagnetic waves
Note 1 to entry: Heat is from molecular agitation in, e.g. gases or atomic agitation in solids.
5.2
total exitance
M
radiant heat flow rate (4.1) emitted by a surface divided by the area of the emitting surface:
dφ
+−
M==qo rq
rr
dA
Note 1 to entry: M is the areal density of the heat flow rate in each point of an emitting surface. It is a total
hemispherical quantity. See Table 1.
Note 2 to entry: Expressed in Wm/ .
ISO 9288:2022(E)
5.3
spectral exitance
M
λ
total exitance (5.2) divided by the spectral interval, centred on the wavelength λ :
dM
+−
M ==qo rq
λλrr,,λ
dλ
Note 1 to entry: Expressed in Wm/ .
5.4
black body
full radiator
Planck radiator
BB
object that absorbs all the incident radiation for all wavelengths, directions and polarizations
Note 1 to entry: At a given temperature, for each wavelength it emits the maximum thermal energy [maximum
spectral exitance (5.3)]. For this reason and because rigorous laws define its emission (5.1), the emission of real
bodies (5.7) is compared with that of the black body.
Note 2 to entry: Terms related to black body bear a superscript notation (°).
5.5
black body total exitance
o
M
quantity defined by the formula:
o 4
MT=σ
where
σ 24
−8
is equal to 5,67 × 10 Wm/ ⋅K ;
()
T
is the absolute temperature of the black body (5.4).
Note 1 to entry: Expressed in Wm/ .
Note 2 to entry: Expressed by the Stefan-Boltzmann law.
Note 3 to entry: Terms related to black body bear a superscript notation (°).
5.6
black body spectral exitance
o
M
λ
quantity defined by the formula:
−5
C λ
o 1
M =
...