ISO 21239

Thermal insulation products for buildings — Reflective insulating products — Specification

Produits d'isolation thermique pour les bâtiments — Produits isolants réfléchissants — Spécification

General Information

• Status: Not Published
• ICS: 91.100.60 - Thermal and sound insulating materials
• Technical Committee: ISO/TC 163/SC 3 - Thermal insulation products, components and systems
• Drafting Committee: ISO/TC 163/SC 3 - Thermal insulation products, components and systems
• Current Stage: 6000 - International Standard under publication
• Start Date: 04-Dec-2025
• Completion Date: 13-Dec-2025

Standards Content (Sample)

FINAL DRAFT
International
Standard
ISO/FDIS 21239
ISO/TC 163/SC 3
Thermal insulation products for
Secretariat: SCC
buildings — Reflective insulating
Voting begins on:
products — Specification
2025-10-08
Voting terminates on:
2025-12-03
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.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
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
ISO/FDIS 21239:2025(en) © ISO 2025

FINAL DRAFT
ISO/FDIS 21239:2025(en)
International
Standard
ISO/FDIS 21239
ISO/TC 163/SC 3
Thermal insulation products for
Secretariat: SCC
buildings — Reflective insulating
Voting begins on:
products — Specification
Voting terminates on:
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 2025
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
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
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
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 Reference number
ISO/FDIS 21239:2025(en) © ISO 2025

ii
ISO/FDIS 21239:2025(en)
Contents Page
Foreword .iv
1 Scope . 1
2  Normative references . 1
3  Terms and definitions . 2
4  Symbols, units and abbreviated terms . 3
4.1 Symbols and units .3
4.2 Abbreviated terms and symbols used in designations.4
5 Requirements . 4
5.1 General .4
5.1.1 Conformance requirements .4
5.1.2 Classification . .4
5.2 Sampling .5
5.3 Preparation .5
5.4 Conditioning.5
5.5 Detailed requirements .5
5.5.1 Thermal resistance .5
5.5.2 Emissivity .6
5.5.3 Dimensions and tolerances requirements .6
5.5.4 Dimensional stability requirements .7
5.5.5 Combustibility .7
5.5.6 Determination of horizontal burning characteristics of small specimens
subjected to a small flame .7
6 Durability requirements . 7
6.1 Durability of emissivity .7
6.2 Durability of thermal resistance against ageing/degradation .7
6.3 Hygrothermal requirements .8
6.3.1 Water-vapour transmission .8
6.3.2 Moisture content .8
6.3.3 Short term water absorption.8
6.3.4 Long term water absorption .8
6.3.5 Long-term water absorption by diffusion .8
6.4 Reflective layer durability .8
6.4.1 Reflective layer(s) adhesive function requirements .8
6.4.2 Reflective layer flexibility requirements.9
6.5 Mildew resistance requirements .9
6.6 Closed cell content requirements .9
7 Test methods . 9
8 Designation code . . 10
9  Evaluation of conformity . .11
9.1 General .11
9.2 Initial type testing .11
9.3 Factory production control .11
9.4 Outer appearance .11
10 Marking and labelling .12
Annex A (normative) Factory-production control .13
Annex B (informative) Additional properties .15
Annex C (informative)  Cross reference of normative ISO International Standards vs EN
Standards . 16
Annex D (normative)  Determination of the emissivity: ε . 17
D
iii
ISO/FDIS 21239:2025(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 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 163, Thermal performance and energy use in
the built environment, Subcommittee SC 3, Thermal insulation products, components and systems.
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
FINAL DRAFT International Standard ISO/FDIS 21239:2025(en)
Thermal insulation products for buildings — Reflective
insulating products — Specification
1 Scope
This document specifies the requirements for factory-made thermal insulating products containing one
or more reflective or low-emissivity surface components, and designed to be used in conjunction with an
incorporated air space, for the thermal insulation of buildings.
This document specifies products manufactured in the form of rolls, boards and sheets, and also covers
products that are used in prefabricated thermal insulation systems and composite panels. Such prefabricated
systems and composite panels are not within the scope of this document. The products specified in this
document are not intended for use in load-bearing applications.
This document does not specify the required level of a given property to be achieved by a product to
demonstrate fitness for purpose in an application. The levels of performance required for a given application
are to be found in project specifications.
This document supersedes EN/ISO 16012
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 846, Plastics — Evaluation of the action of microorganisms
ISO 1182, Reaction to fire tests for products — Non-combustibility test
ISO 1716, Reaction to fire tests for products — Determination of the gross heat of combustion (calorific value)
ISO 4590, Rigid cellular plastics — Determination of the volume percentage of open cells and of closed cells
ISO 4624, Paints and varnishes — Pull-off test for adhesion
ISO 6946, Building components and building elements — Thermal resistance and thermal transmittance —
Calculation methods
ISO 8990, Thermal insulation — Determination of steady-state thermal transmission properties — Calibrated
and guarded hot box
ISO 9229, Thermal insulation — Vocabulary
ISO 9772, Cellular plastics — Determination of horizontal burning characteristics of small specimens subjected
to a small flame
ISO 10456, Building materials and products — Hygrothermal properties — Tabulated design values and
procedures for determining declared and design thermal values
ISO 11925-2, Reaction to fire tests — Ignitability of products subjected to direct impingement of flame — Part 2:
Single-flame source test
ISO 12570, Hygrothermal performance of building materials and products — Determination of moisture content
by drying at elevated temperature

ISO/FDIS 21239:2025(en)
ISO 12572, Hygrothermal performance of building materials and products — Determination of water vapour
transmission properties — Cup method
ISO 12576-1, Thermal insulation — Insulating materials and products for buildings — Conformity control
systems — Part 1: Factory-made products
ISO 16535, Thermal insulating products for building applications — Determination of long-term water
absorption by immersion
ISO 16536, Thermal insulating products for building applications — Determination of long-term water
absorption by diffusion
ISO 16544, Thermal insulating products for building applications — Conditioning to moisture equilibrium under
specified temperature and humidity conditions
ISO 16269-6:2014, Statistical interpretation of data — Part 6: Determination of statistical tolerance intervals
ISO 29465, Thermal insulating products for building applications — Determination of length and width
ISO 29466, Thermal insulating products for building applications — Determination of thickness
ISO 29467, Thermal insulating products for building applications — Determination of squareness
ISO 29472, Thermal insulating products for building applications — Determination of dimensional stability
under specified temperature and humidity conditions
ISO 29767, Thermal insulating products for building applications — Determination of short-term water
absorption by partial immersion
ISO 22097:2023, Thermal insulation for buildings — Reflective insulation products — Determination of thermal
performance
3  Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 9229 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
class
classification of a product by a property bounded by an upper and lower limit and used to differentiate from
other products which fulfil the same function
3.2
emissivity
ratio of the energy radiated from a material's surface to that radiated from a perfect emitter, known as
a blackbody, at the same temperature and wavelength and under the same viewing conditions
3.3
radiation
emission or transmission of energy in the form of waves or particles through space or through a material medium
3.4
reflection
phenomenon by which progressive waves or particles propagate in a new direction in the same medium
after changing directions as a result of collision with another medium

ISO/FDIS 21239:2025(en)
3.5
reflective insulation
thermal insulation product that derives a portion of its claimed thermal performance and properties from
the presence of one or more reflective or low emissivity surfaces incorporated with associated airspace(s)
4  Symbols, units and abbreviated terms
4.1 Symbols and units
b width mm
D inside diameter mm
i
D outside diameter mm
o
d thickness mm
d thickness mm
D
d nominal thickness of the product mm
N
d thickness of the test specimen mm
s
∆ε relative change in width %
b
∆ε relative change in thickness %
d
∆ε relative change in length %
l
ε Emissivity ——
ε declared emissivity
D
ε declared emissivity representing at least 90 % of the production —
90/90
determined with a confidence level of 90 %
l length mm
λ thermal conductivity W/(m⋅K)
λ thermal conductivity W/(m⋅K)
D
μ water vapour diffusion resistance factor —
N number of test results —
S deviation from squareness on length and width mm/m
b
S deviation from squareness on thickness mm
d
σ compressive stress at 10 % deformation kPa
σ compressive strength kPa
m
v tensile strength perpendicular to faces mm
W long term water absorption by partial immersion kg/m2
lp
Wp short-term water absorption kg/m

ISO/FDIS 21239:2025(en)
4.2  Abbreviated terms and symbols used in designations
CS(10\Y) level for compressive stress or compressive strength
DS(TH) value for dimensional stability under specified temperature and relative humidity conditions
FPC factory production control
ITT initial type test
MU value for water vapour diffusion resistance factor
R declared thermal resistance, m2 K/W
D
RI reflective insulation
RtF reaction to fire
RH relative humidity
R 90 % fractile with a confidence level of 90 % for the thermal resistance, m2 K/W
90/90
T class for thickness tolerances
WS level for short term water absorption
CD(V) level for water absorption by diffusion
WL(T) declared level for long term water absorption by total immersion
WL(P) declared level for long term water absorption by partial immersion
Z declared value for water vapour resistance
5 Requirements
5.1 General
5.1.1 Conformance requirements
Reflective insulating products for application as thermal insulation products fir buildings shall conform
with the requirements of this specification
Those additional durability aspects, not applicable to all materials, are set out in Clause 6.
A summary of test methods, test specimens and specific conditions is set out in Table 4 of Clause 7.
5.1.2  Classification
This document is applicable to products which include air spaces and reflective surfaces within the body
of the products, or can possess inner or outer reflective coatings or reflective facings materials. Four
product types are used in the classification of ISO 22097 products. These classifications define the thermal
transmission test methods required to determine and verify classification. The four product types are:
— Product Type 1, includes materials with parallel faces or which can be compressed into parallel faces
without compromising the nominal thickness for testing of thermal resistance when using guarded hot
plate or heat flow meter equipment.
— Product Type 2, has the properties as for Type 1 but can contain indentations of less than 5 mm in width
or depth. Indentations can be grooves, folds, creases or contoured shapes as for containing air bubbles.

ISO/FDIS 21239:2025(en)
— Product Type 3, has external surfaces which are not parallel and can vary considerably in thickness.
— Product Type 4, is a thin film or sheet of less than 2,0 mm thickness.
5.2 Sampling
Test specimens shall be taken from the same product sample of total area not less than 1 m and sufficient
to cover the necessary test methods. The shorter side of the sample shall not be less than 300 mm or full size
of the product. When testing is carried out in accordance with ISO 8990, larger test specimens are required.
Table 4 shows the required test specimen dimensions and the minimum number of test specimens required
to give one test result.
5.3 Preparation
All test specimens shall be cut appropriately for their respective tests at least 50 mm from each edge or
corner of the sample.
If additional layers are to be added to a single-layer product, the test conditions for multi-layered reflective
insulation products shall be applied and a note of such action is made.
5.4 Conditioning
5.4.1 All test specimens used in testing shall have been manufactured not less than 72 h earlier and shall
be conditioned at a temperature range of (23 ± 2) °C with an RH range of (50 ± 10) %, for at least 24 h
immediately prior to testing.
5.4.2 Products with layers of closed cell insulating foam shall be aged for 180 days and conditioned at
a temperature range of (23 ± 2) °C with an RH range of (50 ± 10) %, for at least 24 h immediately prior to
testing.
5.5 Detailed requirements
5.5.1 Thermal resistance
Thermal resistance shall be determined in accordance with ISO 22097.
The thermal resistance shall be declared by the manufacturer according to the following:
— the reference mean temperature shall be 10 °C for temperate climate conditions and 23 °C for tropical
conditions;
— the measured values shall be expressed to three significant decimal places;
— the declared thermal resistance, R , shall be given as a limit value representing at least 90 % of the
D
production, determined with a confidence level of 90 %;
— the declared thermal resistance, R , shall be based upon the nominal thickness (d ), or the measured
D N
thickness (d ) whichever is the lesser thickness; and
L
— the statistical value of thermal resistance, R , shall be rounded downwards to the nearest 0,05 m ⋅K/W,
90/90
and declared as R in levels with steps of 0,05 m ⋅K/W;
D
— R & U (design values) shall be determined in accordance with either ISO 10456 or ISO 6946, or both, for
air spaces.
ISO/FDIS 21239:2025(en)
5.5.2  Emissivity
The emissivity of the reflective surface or surfaces shall be determined in accordance with the test method
set out in Annex D to this document.
Measured values shall be declared by the manufacturer as follows:
— the measured value shall be expressed to two significant figures;
— the declared value of emissivity ε shall be given as a limit value representing at least 90 % of the
production, determined with a confidence level of 90 %;
— the statistical value of emissivity ε shall be declared for each external face of the product if the two
90/90
faces differ (including the presence of printing on any face), otherwise the declared value may be the
mean value for the two faces provided they do not differ by more than 0,01; and
— the statistical value of emissivity shall be rounded upwards to the nearest 0,01. Values less than 0,05
shall be declared as 0,05.
5.5.3 Dimensions and tolerances requirements
5.5.3.1 Specimen preparation
5.5.3.1.1 General
For test specimens of reflective insulation products in sheet form, test specimens longer than 500 mm shall
be cut from a roll and at points greater than 20 mm from each edge or ends of the roll. Specimens shall be
conditioned immediately prior to the test for 24 h at 23 °C and 90 % RH or aged for 180 days under the same
conditions if the composit
...

ISO/DISFDIS 21239:2024(en)
ISO/TC 163/SC 3
Secretariat: SCC
Draft rev 2025-07-05
Date:
Thermal insulation products for buildings — Reflective insulating
products — Specification
FDIS stage
ISO CD 21239
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
E-mail: [e-mail]
Website: www.iso.orgProduits isolants thermiques pour le bâtiment— Produits d'isolation thermique
réfléchissant
ISO/FDIS 21239:2025(en)
Published in Switzerland
iii
ISO/FDIS 21239:2025(en)
Contents Page
Foreword . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols, units and abbreviated terms . 3
4.1 Symbols and units . 3
4.2 Abbreviated terms and symbols used in designations. 4
5 Requirements . 4
5.1 General . 4
5.2 Sampling . 5
5.3 Preparation . 5
5.4 Conditioning . 5
5.5 Detailed requirements . 5
6 Durability requirements . 8
6.1 Durability of emissivity . 8
6.2 Durability of thermal resistance against ageing/degradation . 8
6.3 Hygrothermal requirements . 8
6.4 Reflective layer durability . 9
6.5 Mildew resistance requirements . 9
6.6 Closed cell content requirements . 10
7 Test methods . 10
8 Designation code . 11
9 Evaluation of conformity . 12
9.1 General . 12
9.2 Initial type testing . 12
9.3 Factory production control . 12
9.4 Outer appearance . 12
10 Marking and labelling . 12
Annex A (normative) Factory-production control . 14
Annex B (informative) Additional properties . 16
Annex C (informative) Cross reference of normative ISO International Standards vs EN
Standards . 17
Annex D (normative) Determination of the emissivity: ε . 18
D
Bibliography . 22

iv
ISO/FDIS 21239:2025(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 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 163, Thermal performance and energy use in the
built environment, Subcommittee SC 3, Thermal insulation products, components and systems.
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.
v
ISO/FDIS 21239:2025(en)
Thermal insulation products for buildings — Reflective insulating
products –— Specification
1 Scope
This document specifies the requirements for factory-made thermal insulating products containing one or
more reflective or low-emissivity surface components, and designed to be used in conjunction with an
incorporated air space, for the thermal insulation of buildings.
This document specifies products manufactured in the form of rolls, boards and sheets, and also covers
products that are used in prefabricated thermal insulation systems and composite panels. Such prefabricated
systems and composite panels are not within the scope of this document. The products specified in this
document are not intended for use in load-bearing applications.
This document does not specify the required level of a given property to be achieved by a product to
demonstrate fitness for purpose in an application. The levels of performance required for a given application
are to be found in project specifications.
This document supersedes EN/ISO 16012
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 846, Plastics — Evaluation of the action of microorganisms
ISO 1182, Reaction to fire tests for products — Non-combustibility test
ISO 1716, Reaction to fire tests for products — Determination of the gross heat of combustion (calorific value)
ISO 4590, Rigid cellular plastics — Determination of the volume percentage of open cells and of closed cells
ISO 4624, Paints and varnishes — Pull-off test for adhesion
ISO 6946, Building components and building elements — Thermal resistance and thermal transmittance —
Calculation methods
ISO 8990, Thermal insulation — Determination of steady-state thermal transmission properties — Calibrated
and guarded hot box
ISO 9229, Thermal insulation — Vocabulary
ISO 9772, Cellular plastics — Determination of horizontal burning characteristics of small specimens subjected
to a small flame
ISO 10456, Building materials and products — Hygrothermal properties — Tabulated design values and
procedures for determining declared and design thermal values
ISO 11925--2, Reaction to fire tests — Ignitability of products subjected to direct impingement of flame — Part
2: Single-flame source test
ISO/FDIS 21239:2025(en)
ISO 12570, Hygrothermal performance of building materials and products — Determination of moisture content
by drying at elevated temperature
ISO 12572, Hygrothermal performance of building materials and products — Determination of water vapour
transmission properties — Cup method
ISO 12576--1, Thermal insulation — Insulating materials and products for buildings — Conformity control
systems — Part 1: Factory-made products
ISO 16535, Thermal insulating products for building applications — Determination of long-term water
absorption by immersion
ISO 16536, Thermal insulating products for building applications — Determination of long-term water
absorption by diffusion
ISO 16544, Thermal insulating products for building applications — Conditioning to moisture equilibrium under
specified temperature and humidity conditions
ISO 16269-6:2014, Statistical interpretation of data — Part 6: Determination of statistical tolerance intervals
ISO 29465, Thermal insulating products for building applications — Determination of length and width
ISO 29466, Thermal insulating products for building applications — Determination of thickness
ISO 29467, Thermal insulating products for building applications — Determination of squareness
ISO 29472, Thermal insulating products for building applications — Determination of dimensional stability
under specified temperature and humidity conditions
ISO 29767, Thermal insulating products for building applications — Determination of short-term water
absorption by partial immersion
ISO 22097:2023, Thermal insulation for buildings — Reflective insulation products — Determination of thermal
performance
A cross reference of EN documents to the above is presented for reference in Annex C of this document
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 9229 and the following apply.
ISO and IEC maintain terminologicalterminology 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
class
classification of a product by a property bounded by an upper and lower limit and used to differentiate from
other products which fulfil the same function
ISO/FDIS 21239:2025(en)
3.2 3.2
emissivity
ratio of the energy radiated from a material's surface to that radiated from a perfect emitter, known as
a blackbody, at the same temperature and wavelength and under the same viewing conditions.
3.3 3.3
radiation
emission or transmission of energy in the form of waves or particles through space or through a material
medium
3.4 3.4
reflection
phenomenon by which progressive waves or particles propagate in a new direction in the same medium after
changing directions as a result of collision with another medium
3.5 3.5
reflective insulation
thermal insulation product that derives a portion of its claimed thermal performance and properties from the
presence of one or more reflective or low emissivity surfaces incorporated with associated airspace(s)
4 Symbols, units and abbreviated terms
4.1 Symbols and units
b width mm
D inside diameter mm
i
D outside diameter mm
o
d thickness mm
d thickness mm
D
d nominal thickness of the product mm
N
d thickness of the test specimen mm
s
∆ε relative change in width %
b
∆ε relative change in thickness %
d
∆ε relative change in length %
l
ε Emissivity ——
ε declared emissivity
D
ε declared emissivity representing at least 90 % of the production —
90/90
determined with a confidence level of 90 %
l length mm
λ thermal conductivity W/(m⋅K)
λ thermal conductivity W/(m⋅K)
D
μ water vapour diffusion resistance factor —
N number of test results —
S deviation from squareness on length and width mm/m
b
S deviation from squareness on thickness mm
d
ISO/FDIS 21239:2025(en)
σ compressive stress at 10 % deformation kPa
σ compressive strength kPa
m
v tensile strength perpendicular to faces mm
W long term water absorption by partial immersion kg/m2
lp
Wp short-term water absorption kg/m
4.2 Abbreviated terms and symbols used in designations
CS(10\Y) level for compressive stress or compressive strength
DS(TH) value for dimensional stability under specified temperature and relative humidity conditions
FPC factory production control
ITT initial type test
MU value for water vapour diffusion resistance factor
R declared thermal resistance, m2 ·K/W
D
RI reflective insulation
RtF reaction to fire
RH relative humidity
R
90/90 90 % fractile with a confidence level of 90 % for the thermal resistance, m2 ·K/W
T class for thickness tolerances
WS level for short term water absorption
CD(V) level for water absorption by diffusion
WL(T) declared level for long term water absorption by total immersion
WL(P) declared level for long term water absorption by partial immersion
Z declared value for water vapour resistance
5 Requirements
5.1 General
5.1.1 Conformance requirements
Reflective insulating products for application as thermal insulation products fir buildings shall complyconform
with the requirements of this specification
Those additional durability aspects, not applicable to all materials, are set out in Clause 6paragraph 6.0.
A summary of test methods, test specimens and specific conditions is set out in Table 4Table 4 of
Clause 7Clause 7.
5.1.2 Classification
This document is applicable to products which include air spaces and reflective surfaces within the body of
the products, or maycan possess inner or outer reflective coatings or reflective facings materials. Four Product
Typesproduct types are used in the classification of ISO 22097 products. These classifications define the
ISO/FDIS 21239:2025(en)
thermal transmission test methods required to determine and verify classification. The four Product
Typesproduct types are:
— — Product Type 1, includes materials with parallel faces or which can be compressed into parallel faces
without compromising the nominal thickness for testing of thermal resistance when using guarded hot
plate or heat flow meter equipment.
— — Product Type 2, has the properties as for Type 1 but maycan contain indentations of less than 5 mm in
width or depth. Indentations can be grooves, folds, creases or contoured shapes as for containing air
bubbles.
— — Product Type 3, has external surfaces which are not parallel and can vary considerably in thickness.
— — Product Type 4, is a thin film or sheet of less than 2,0 mm thickness.
5.2 Sampling
Test specimens shall be taken from the same product sample of total area not less than 1 m and sufficient to
cover the necessary test methods. The shorter side of the sample shall not be less than 300 mm or full size of
the product. IfWhen testing is carried out in accordance with ISO 8990, larger test specimens are required.
Table 4Table 4 shows the required test specimen dimensions and the minimum number of test specimens
required to give one test result.
5.3 Preparation
All test specimens shall be cut appropriately for their respective tests at least 50 mm from each edge or corner
of the sample.
If additional layers are to be added to a single-layer product, the test conditions for multi-layered reflective
insulation products shall be applied and a note of such action is made.
5.4 Conditioning
5.4.1 5.4.1 All test specimens used in testing shall have been manufactured not less than 72 h earlier and
shall be conditioned at a temperature range of (23 ± 2) °C with an RH range of (50 ± 10) %, for at least 24 h
immediately prior to testing.
5.4.2 5.4.2 Products with layers of closed cell insulating foam shall be aged for 180 days and conditioned
at a temperature range of (23 ± 2) °C with an RH range of (50 ± 10) %, for at least 24 h immediately prior to
testing.
5.5 Detailed requirements
5.5.1 Thermal resistance
Thermal resistance shall be determined in accordance with ISO 22097, as defined therein.
The thermal resistance shall be declared by the manufacturer according to the following:
— — the reference mean temperature shall be 10 °C for temperate climate conditions and 23 °C for tropical
conditions;
— — the measured values shall be expressed to three significant decimal places;
ISO/FDIS 21239:2025(en)
— — the declared thermal resistance, R , shall be given as a limit value representing at least 90 % of the
D
production, determined with a confidence level of 90 %;
— — the declared thermal resistance, R , shall be based upon the nominal thickness (d ), or the measured
D N
thickness (d ) whichever is the lesser thickness; and
L
— — the statistical value of thermal resistance, R , shall be rounded downwards to the nearest
90/90
2 2
0,05 m⋅K/W, and declared as R in levels with steps of 0,05 m⋅K/W;
D
— — R & U (design values) canshall be determined in accordance with either ISO 10456 and/or ISO 6946,
or both, for air spaces.
5.5.2 Emissivity
The emissivity of the reflective surface or surfaces shall be determined in accordance with the test method set
out in Annex DAnnex D to this document.
Measured values shall be declared by the manufacturer as follows:
— — the measured value shall be expressed to two significant figures;
— — the declared value of emissivity ε shall be given as a limit value representing at least 90 % of the
production, determined with a confidence level of 90 %;
— — the statistical value of emissivity ε shall be declared for each external face of the product if the two
90/90
faces differ (including the presence of printing on any face), otherwise the declared value may be the mean
value for the two faces provided they do not differ by more than 0,01; and
— — the statistical value of emissivity shall be rounded upwards to the nearest 0,01. Values less than 0,05
shall be declared as 0,05.
5.5.3 Dimensions and tolerances requirements
5.5.3.1 5.5.3.1 Specimen preparation
5.5.3.1.1 General
For test specimens of reflective insulation products in sheet form, test specimens longer than 500 mm shall
be cut from a roll and at points greater than 20 mm from each edge or ends of the roll. Specimens shall be
conditioned immediately prior to the test for 24 h at 23 °C and 90 % RH or aged for 180 days under the same
conditions if the composition incudes any layers of closed cell polymeric foam materials.
5.5.3.1.15.5.3.1.2 5.5.3.2.1 Linear dimensions requirements (length and width)
The length, l and width, b, for flat products shall be determined in accordance with ISO 29465 and ISO 29466.
Thickness shall be measured with a device having a maximum permissible measurement error of 0,1 mm or
better. In the case of partially packed products, measurement shall be made with the packed portion.
Thickness tolerances shall be in accordance with Table 1Table 1. No test result shall deviate from the declared
values by more than the tolerances given in Table 1Table 1
ISO/FDIS 21239:2025(en)
Table 1 — Levels and classes for thickness tolerances
Class Tolerances
a b
T1 -5 % or – 5 mm +5 mm
a b
T2 -5 % or – 5 mm +15 % or +5 mm
a Whichever gives the greatest numerical tolerance.
b Whichever gives the smallest numerical tolerance.
5.5.3.1.2
5.5.3.1.3 5.5.3.2.2 Linear dimensions requirements (thickness)
The nominal thickness, d, of rolls, boards and sheets shall be determined in accordance with ISO 29466. The
load applied in the thickness determination shall be by application of the lowest test pressure necessary to
eliminate material air spaces which are not part of the construction and not less than the pressures as in
Table 2Table 2.
The actual test pressure applied to eliminate air gaps and to achieve substantial contact with test plates (if
any), the thickness of the tested sample and the recovery time to be allowed to achieve the nominal thickness
shall be stated.
Table 2 — Minimum load for thickness measurements
Product description Load Pa
Highly compressible 3
Semi-rigid 25
Rigid 250
5.5.3.2 5.5.3.3 Squareness
The squareness, S , of boards shall be determined in accordance with ISO 29467 for boards less than 5 m in
b
length. Deviations from squareness of length and width of boards shall not exceed 10 mm/m.
5.5.4 Dimensional stability requirements
Dimensional stability under specified temperature and humidity conditions shall be determined in accordance
with ISO 29472
The relative change in thickness, ∆δ , shall not result in a reduction exceeding 0,3 %. The relative changes in
d
length, Δδ , and width, Δδ , shall not exceed 0,3 %. The relative change in flatness, Δδ shall not exceed
l b s
0,3 mm/m.
5.5.5 Combustibility
Products which are non-combustible according to ISO 1182 shall be classified as such and may be reported as
being non-combustible.
For products whic
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