ISO 13837:2021

Road vehicles — Safety glazing materials — Method for the determination of solar transmittance

This document specifies test methods to determine the luminous, the direct and total solar transmittance, and the colorimetry of safety glazing materials for road vehicles. This document applies to monolithic or laminated, clear or tinted samples of safety glazing materials. Essentially flat sections of glazing parts can be used in this test, as well as flat samples of the same materials.

Véhicules routiers — Vitrages de sécurité — Méthode de détermination du facteur de transmission du rayonnement solaire

General Information

• Status: Published
• Publication Date: 27-Sep-2021
• ICS: 43.040.60 - Bodies and body components
• ICS: 81.040.30 - Glass products
• Technical Committee: ISO/TC 22/SC 35 - Lighting and visibility
• Drafting Committee: ISO/TC 22/SC 35/WG 2 - Safety glazing
• Current Stage: 6060 - International Standard published
• Start Date: 28-Sep-2021
• Due Date: 15-Jun-2021
• Completion Date: 28-Sep-2021

Relations

• Revises: ISO 13837:2008 - Road vehicles — Safety glazing materials — Method for the determination of solar transmittance
• Effective Date: 23-Jun-2018
• Consolidated By: ISO 3262-22:2023 - Extenders — Specifications and methods of test — Part 22: Flux-calcined kieselguhr
• Effective Date: 06-Jun-2022

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 13837
Second edition
2021-09
Road vehicles — Safety glazing
materials — Method for the
determination of solar transmittance
Véhicules routiers — Vitrages de sécurité — Méthode de
détermination du facteur de transmission du rayonnement solaire
Reference number
ISO 13837:2021(E)
©
ISO 2021

---------------------- Page: 1 ----------------------
ISO 13837:2021(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
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 2021 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 13837:2021(E)

Contents Page
Foreword .iv
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
3.1 Terms and definitions . 1
3.2 Symbols . 1
4 Apparatus . 2
5 Procedure. 2
5.1 Sample preparation . 2
5.2 Measurement . 3
5.3 Calculation method . 3
5.3.1 Luminous transmittance [T ] . 3
L
5.3.2 Solar UV transmittance [T ] . 3
UV 338800
()
5.3.3 Solar UV transmittance [T ] . 3
UV 440000
()
5.3.4 Solar direct transmittance [T ] . 3
e
5.3.5 Solar direct reflectance [R ] . 3
e
5.3.6 Solar direct absorbance [a ] . 4
e
5.3.7 Total solar transmittance [T ] . 4
TS
5.3.8 Colorimetry . 5
6 Expression of results . 6
Annex A (informative) Derivation of solar weight table .10
Bibliography .12
© ISO 2021 – All rights reserved iii

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ISO 13837:2021(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 22, Road vehicles, Subcommittee SC 35,
Lighting and visibility.
This second edition cancels and replaces the first edition (ISO 13837:2008), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— deletion of definitions of convention “A” and convention “B”;
— deletion of all texts and tables corresponding to air mass 1,0 global;
— revision of 3.1;
— addition of some symbol definitions for variables and parameters;
— addition of calculation methods for luminous transmittance [T ], solar direct reflectance [R ], solar
L e
direct absorbance [ a ] and colorimetry;
e
 
— revision of calculation method for solar UV transmittance T to calculate with air mass 1,5
UV 380
()
 
global;
— addition of a new Table 1 for calculation of luminous transmittance [T ], a new Table 2 for calculation
L
of solar UV transmittance [T ], and a new Table 5 for calculation of colorimetry;
UV()380
— revision of Table 3 (former Table 1) for calculation of solar UV transmittance [T ], Table 4
UV()400
(former Table 2) for calculation of solar direct transmittance []T , solar direct reflectance []R , and
e e
Table A.1 for explanation of the derivation process;
— revision of Annex A to list the source of values in the new solar weight tables and give out the
derivation process of Table 3 as an example;
iv © ISO 2021 – All rights reserved

---------------------- Page: 4 ----------------------
ISO 13837:2021(E)

— deletion of Figure A.1 and Figure A.2;
— moving of texts of Annex B to 5.3.7 and revision of text structure;
— revision of Bibliography;
— editorial update.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
© ISO 2021 – All rights reserved v

---------------------- Page: 5 ----------------------
ISO 13837:2021(E)

Introduction
A review of existing standards and industry specifications and procedures reveals a lack of agreement
with respect to the basis for defining and measuring the ultraviolet (UV), visible (VIS), infrared (IR)
transmittance and colorimetry (L*, a*, b*) properties of glazing materials. To avoid the continued
preparation and promulgation of conflicting standards by individual entities, there is an interest in the
automotive and glazing industries to harmonize on a worldwide basis the test procedures and protocols
used to assess the solar transmittance properties of glazing materials.
vi © ISO 2021 – All rights reserved

---------------------- Page: 6 ----------------------
INTERNATIONAL STANDARD ISO 13837:2021(E)
Road vehicles — Safety glazing materials — Method for the
determination of solar transmittance
1 Scope
This document specifies test methods to determine the luminous, the direct and total solar
transmittance, and the colorimetry of safety glazing materials for road vehicles.
This document applies to monolithic or laminated, clear or tinted samples of safety glazing materials.
Essentially flat sections of glazing parts can be used in this test, as well as flat samples of the same
materials.
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/CIE 11664-4:2019, Colorimetry — Part 4: CIE 1976 L*a*b* colour space
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions 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/
3.1.1
air mass
ratio of the mass of atmosphere in the actual observer-sun path to the mass that would exist if the
observer were at sea level, at standard barometric pressure, and the sun were directly overhead
3.2 Symbols
T
luminous transmittance for CIE standard illuminant A with 2 degree view
L
through a glazing
T
transmittance through a glazing at wavelength λ within a specified Δλ
λ
W normalized luminous transmittance weighting coefficient
λ
T
ultraviolet (UV) direct solar energy transmitted through the glazing at a
UV()380
specified upper limit value (380 nm)
′
normalized relative spectral distribution of global solar radiation
E
λ()n
T
ultraviolet (UV) direct solar energy transmitted through the glazing at a
UV 400
()
specified upper limit value (400 nm)
© ISO 2021 – All rights reserved 1

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ISO 13837:2021(E)

T
direct solar energy (e) transmitted through the glazing
e
R
direct solar energy (e) reflected by the glazing
e
R
external reflectance (R) of a glazing at wavelength λ within a specified Δλ
λ
a
direct solar energy (e) absorbed by the glazing
e
T total solar energy (T + q ) transmitted through the glazing
TS e i
q
secondary heat flux through the glazing
i
h
heat flux of the safety glazing material towards the outside
e
h
heat flux of the safety glazing material towards the inside
i
v wind velocity
ε
corrected emissivity
i
X , Y , Z
tristimulus values calculated using the CIE 1964 standard colorimetric ob-
10 10 10
server under CIE standard illuminant D65 spectral power distribution
WW,, W
pre-calculated weighting functions for tristimulus integration using the
10,,XYλλ10 10,Z λ
() () ()
CIE 1964 standard colorimetric observer
X , Y , Z
tristimulus values of a specific white colour stimulus calculated using the
n n n
colour-matching functions of the CIE 1931 standard colorimetric system
* * *
coordinates of the CIE 1976 L*a*b* colour space; L*, CIELAB lightness; a*, b*,
L , a , b
CIELAB coordinates
λ wavelength, in nm
S relative spectral distribution of global solar radiation
λ
Δλ uniform λ interval
E
solar energy within a Δλ
λ
′
E in trapezoidal form ( E /2, E … E , E /2)
E
λ 1 2 n−1 n
λ
4 Apparatus
This method requires spectral transmittance data to be obtained from samples of glazing materials
using a scanning spectrophotometer. This instrument, preferably equipped with an integrating sphere,
shall be capable of measuring transmittance over that part of the electromagnetic spectrum in which
the solar energy is transmitted to the earth's surface.
5 Procedure
5.1 Sample preparation
Cut out (if necessary) and clean the flattest area of curved test specimens with distilled water and
reagent grade ethanol, or use an alternate procedure appropriate to the material, if necessary. Cut and
clean flat samples similarly.
2 © ISO 2021 – All rights reserved

---------------------- Page: 8 ----------------------
ISO 13837:2021(E)

5.2 Measurement
Standardize the spectrophotometer in accordance with the manufacturer's instructions. Measure
transmittance/reflectance of cleaned sample and record the sample spectral data in accordance with
the instrument manufacturer's recommendation. Note its film/coating side and curvature orientation,
if applicable.
5.3 Calculation method
5.3.1 Luminous transmittance [T ]
L
The luminous transmittance T shall be calculated using the weight data of visible radiation of CIE
L
standard illuminant A in Table 1 and Formula (1):
780
TT=×W (1)
L ∑ λλ
380
5.3.2 Solar UV transmittance [T ]
UV 338800
()
The solar UV transmittance T shall be calculated using the solar weight data in Table 2 and
UV()380
Formula (2):
380
′
TT=×E (2)
UV 380 ∑ λ λ n
() ()
300
5.3.3 Solar UV transmittance [T ]
UV()440000
The solar UV transmittance T shall be calculated using the solar weight data in Table 3 and
UV 400
()
Formula (3):
400
′
TT=×E (3)
UV()400 ∑ λ λ()n
300
NOTE Annex A gives out an example of the derivation process for Table 3.
5.3.4 Solar direct transmittance [T ]
e
The solar direct transmittance T shall be calculated using the solar weight data in Table 4 and
e
Formula (4):
2 500
′
TT=×E (4)
e λ
∑ λ()n
300
5.3.5 Solar direct reflectance [R ]
e
The solar direct reflectance Rshall be calculated using the solar weight data in Table 4 and
e
Formula (5):
2 500
′
RR=×E (5)
e ∑ λ λ()n
300
© ISO 2021 – All rights reserved 3

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ISO 13837:2021(E)

5.3.6 Solar direct absorbance [a ]
e
The solar direct absorbance a shall be calculated using Formula (6):
e
aT=−100 −R (6)
ee e
where 100 is expressed in percentage (%).
5.3.7 Total solar transmittance [T ]
TS
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 13837
ISO/TC 22/SC 35
Road vehicles — Safety glazing
Secretariat: UNI
materials — Method for the
Voting begins on:
2021­06­16 determination of solar transmittance
Voting terminates on:
Véhicules routiers — Vitrages de sécurité — Méthode de
2021­08­11
détermination du facteur de transmission du rayonnement solaire
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
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/FDIS 13837:2021(E)
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. ISO 2021

---------------------- Page: 1 ----------------------
ISO/FDIS 13837:2021(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
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
CH­1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved

---------------------- Page: 2 ----------------------
ISO/FDIS 13837:2021(E)

Contents Page
Foreword .iv
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
3.1 Terms and definitions . 1
3.2 Symbols . 1
4 Apparatus . 2
5 Procedure. 2
5.1 Sample preparation . 2
5.2 Measurement . 3
5.3 Calculation method . 3
5.3.1 Luminous transmittance [T ] . 3
L
5.3.2 Solar UV transmittance [T ] . 3
UV 338800
()
5.3.3 Solar UV transmittance [T ] . 3
UV 440000
()
5.3.4 Solar direct transmittance [T ] . 3
e
5.3.5 Solar direct reflectance [R ] . 3
e
5.3.6 Solar direct absorbance [a ] . 4
e
5.3.7 Total solar transmittance [T ] . 4
TS
5.3.8 Colorimetry . 5
6 Expression of results . 6
Annex A (informative) Derivation of solar weight tables in this document .10
Bibliography .12
© ISO 2021 – All rights reserved iii

---------------------- Page: 3 ----------------------
ISO/FDIS 13837:2021(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 non­governmental, 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 22, Road vehicles, Subcommittee SC 35,
Lighting and visibility.
This second edition cancels and replaces the first edition (ISO 13837:2008), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— deletion of definitions of convention “A” and convention “B”;
— deletion of all texts and tables corresponding to air mass 1,0 global;
— revision of 3.1;
— addition of some symbol definitions for variables and parameters;
— addition of calculation methods for luminous transmittance [T ], solar direct reflectance [R ], solar
L e
direct absorbance [ a ] and colorimetry;
e
 
— revision of calculation method for solar UV transmittance T to calculate with air mass 1,5
UV 380
()
 
global;
— addition of a new Table 1 for calculation of luminous transmittance [T ], a new Table 2 for calculation
L
of solar UV transmittance [T ], and a new Table 5 for calculation of colorimetry;
UV()380
— revision of Table 3 (former Table 1) for calculation of solar UV transmittance [T ], Table 4
UV()400
(former Table 2) for calculation of solar direct transmittance []T and solar direct reflectance []R
e e
, and Table A.1 for explanation of derivation process;
— revision of Annex A to list the source of values in the new solar weight tables and give out the
derivation process of Table 3 as an example;
iv © ISO 2021 – All rights reserved

---------------------- Page: 4 ----------------------
ISO/FDIS 13837:2021(E)

— deletion of Figure A.1 and Figure A.2;
— moving of texts of Annex B to 5.3.7 and revision of text structure;
— revision of Bibliography;
— editorial update.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
© ISO 2021 – All rights reserved v

---------------------- Page: 5 ----------------------
ISO/FDIS 13837:2021(E)

Introduction
A review of existing standards and industry specifications and procedures reveals a lack of agreement
with respect to the basis for defining and measuring the ultraviolet (UV), visible (VIS), infrared (IR)
transmittance and colorimetry (L*, a*, b*) properties of glazing materials. To avoid the continued
preparation and promulgation of conflicting standards by individual entities, there is an interest in the
automotive and glazing industries to harmonize on a worldwide basis the test procedures and protocols
used to assess the solar transmittance properties of glazing materials.
vi © ISO 2021 – All rights reserved

---------------------- Page: 6 ----------------------
FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 13837:2021(E)
Road vehicles — Safety glazing materials — Method for the
determination of solar transmittance
1 Scope
This document specifies test methods to determine the luminous, the direct and total solar
transmittance, and the colorimetry of safety glazing materials for road vehicles.
This document applies to monolithic or laminated, clear or tinted samples of safety glazing materials.
Essentially flat sections of glazing parts can be used in this test, as well as flat samples of the same
materials.
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/CIE 11664­4:2019, Colorimetry — Part 4: CIE 1976 L*a*b* colour space
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1.1
air mass
ratio of the mass of atmosphere in the actual observer-sun path to the mass that would exist if the
observer were at sea level, at standard barometric pressure, and the sun were directly overhead
3.2 Symbols
T
luminous transmittance for CIE standard illuminant A with 2 degree view
L
through a glazing
T
transmittance through a glazing at wavelength λ within a specified Δλ
λ
W normalized luminous transmittance weighting coefficient
λ
T
ultraviolet (UV) direct solar energy transmitted through the glazing at a
UV()380
specified upper limit value (380 nm)
′
normalized relative spectral distribution of global solar radiation
E
λ()n
T
ultraviolet (UV) direct solar energy transmitted through the glazing at a
UV 400
()
specified upper limit value (400 nm)
© ISO 2021 – All rights reserved 1

---------------------- Page: 7 ----------------------
ISO/FDIS 13837:2021(E)

T
direct solar energy (e) transmitted through the glazing
e
R
direct solar energy (e) reflected by the glazing
e
R
external reflectance (R) of a glazing at wavelength λ within a specified Δλ
λ
a
direct solar energy (e) absorbed by the glazing
e
T total solar energy (T + q ) transmitted through the glazing
TS e i
q
secondary heat flux through the glazing
i
h
heat flux of the safety glazing material towards the outside
e
h
heat flux of the safety glazing material towards the inside
i
v wind velocity
ε
corrected emissivity
i
X , Y , Z
tristimulus values calculated using the CIE 1964 standard colorimetric
10 10 10
observer under CIE standard illuminant D65 spectral power distribution
WW,, W
pre­calculated weighting functions for tristimulus integration using the
10,,XYλλ10 10,Z λ
() () ()
CIE 1964 standard colorimetric observer
X , Y , Z
tristimulus values of a specific white colour stimulus calculated using the
n n n
colour-matching functions of the CIE 1931 standard colorimetric system
* * *
coordinates of the CIE 1976 L*a*b* colour space; L*, CIELAB lightness; a*,
L , a , b
b*, CIELAB coordinates
λ wavelength, in nm
S relative spectral distribution of global solar radiation
λ
Δλ uniform λ interval
E
solar energy within a Δλ
λ
′
E in trapezoidal form ( E /2, E … E , E /2)
E
λ 1 2 n−1 n
λ
4 Apparatus
This method requires spectral transmittance data to be obtained from samples of glazing materials
using a scanning spectrophotometer. This instrument, preferably equipped with an integrating sphere,
shall be capable of measuring transmittance over that part of the electromagnetic spectrum in which
the solar energy is transmitted to the earth's surface.
5 Procedure
5.1 Sample preparation
Cut out (if necessary) and clean the flattest area of curved test specimens with distilled water and
reagent grade ethanol, or use an alternate procedure appropriate to the material, if necessary. Cut and
clean flat samples similarly.
2 © ISO 2021 – All rights reserved

---------------------- Page: 8 ----------------------
ISO/FDIS 13837:2021(E)

5.2 Measurement
Standardize the spectrophotometer in accordance with the manufacturer's instructions. Measure
transmittance/reflectance of cleaned sample and record the sample spectral data in accordance with
the instrument manufacturer's recommendation. Note its film/coating side and curvature orientation,
if applicable.
5.3 Calculation method
5.3.1 Luminous transmittance [T ]
L
The luminous transmittance T shall be calculated using the weight data of visible radiation of CIE
L
standard illuminant A in Table 1 and Formula (1):
780
TT=×W (1)
L ∑ λλ
380
5.3.2 Solar UV transmittance [T ]
UV 338800
()
The solar UV transmittance T shall be calculated using the solar weight data in Table 2 and
UV()380
Formula (2):
380
′
TT=×E (2)
UV 380 ∑ λ λ n
() ()
300
5.3.3 Solar UV transmittance [T ]
UV()440000
The solar UV transmittance T shall be calculated using the solar weight data in Table 3 and
UV 400
()
Formula (3):
400
′
TT=×E (3)
UV()400 ∑ λ λ()n
300
NOTE Annex A gives out an example of derivation process for Table 3.
5.3.4 Solar direct transmittance [T ]
e
The solar direct transmittance T shall be calculated using the solar weight data in Table 4 and
e
Formula (4):
2 500
′
TT=×E (4)
e λ
∑ λ()n
300
5.3.5 Solar direct reflectance [R ]
e
The solar direct reflectance Rshall be calculated using the solar weight data in Table 4 and
e
Formula (5):
2 500
′
RR=×E (5)
e ∑ λ λ()n
300
© ISO 2021 – All rights reserved 3

---------------------- Page: 9 ----------------------
ISO/FDIS 13837:2021(E)

5.3.6 Solar d
...