ISO/DIS 9050

Glass in building -- Determination of light transmittance, solar direct transmittance, total solar energy transmittance, ultraviolet transmittance and related glazing factors

Verre dans la construction -- Détermination de la transmission lumineuse, de la transmission solaire directe, de la transmission énergétique solaire totale, de la transmission de l'ultraviolet et des facteurs dérivés des vitrages

Standards Content (sample)

DRAFT INTERNATIONAL STANDARD
ISO/DIS 9050
ISO/TC 160/SC 2 Secretariat: ANSI
Voting begins on: Voting terminates on:
2014-04-28 2014-07-28
Glass in building — Determination of light transmittance,
solar direct transmittance, total solar energy
transmittance, ultraviolet transmittance and related
glazing factors

Verre dans la construction — Détermination de la transmission lumineuse, de la transmission solaire

directe, de la transmission énergétique solaire totale, de la transmission de l’ultraviolet et des facteurs

dérivés des vitrages
[Revision of second edition (ISO 9050:2003)]
ICS: 81.040.20
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 9050:2014(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION. ISO 2014
---------------------- Page: 1 ----------------------
ISO/DIS 9050:2014(E)
Copyright notice

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ii © ISO 2014 – All rights reserved
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ISO 9050:2003(E)
Contents Page

Foreword ......................................................................................................................................................... iv

1 Scope ................................................................................................................................................... 1

2 Normative references ......................................................................................................................... 1

3 Determination of characteristic parameters ..................................................................................... 2

3.1 General ................................................................................................................................................ 2

3.2 Performance of optical measurements ............................................................................................. 2

3.3 Light transmittance ............................................................................................................................. 3

3.4 Light reflectance ................................................................................................................................. 5

3.5 Total solar energy transmittance (solar factor) ................................................................................ 6

3.6 UV-transmittance .............................................................................................................................. 14

3.7 CIE damage factor ............................................................................................................................ 14

3.8 Skin damage factor ........................................................................................................................... 15

3.9 Colour rendering ............................................................................................................................... 15

4 Reference values .............................................................................................................................. 16

5 Test report ......................................................................................................................................... 16

Annex A (normative) Calculation procedures ..............................................................................................22

Bibliography ................................................................................................................................................... 27

© ISO 2003 — All rights reserved iii
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ISO 9050:2003(E)XX
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 9050 was prepared by Technical Committee ISO/TC 160, Glass in building, Subcommittee SC 2, Use

considerations.

This second edition cancels and replaces the first edition (ISO 9050:1990) and second edition (ISO 9050:

2003), which has been technically revised.
iv © ISO 2003 — All rights reserved
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INTERNATIONAL STANDARD ISO 9050:2003(E)
Glass in building — Determination of light transmittance, solar
direct transmittance, total solar energy transmittance,
ultraviolet transmittance and related glazing factors
1 Scope

This International Standard specifies methods of determining light and energy transmittance of solar radiation

for glazing in buildings. These characteristic data can serve as a basis for light, heating and ventilation

calculations of rooms and can permit comparison between different types of glazing.

This International Standard is applicable both to conventional glazing units and to absorbing or reflecting

solar-control glazing, used as glazed apertures. The appropriate formulae for single, double and triple glazing

are given. Furthermore, the general calculation procedures for units consisting of more than components are

established.

This International Standard is applicable to all transparent materials. One exception is the treatment of the

secondary heat transfer factor and the total solar energy factor for those materials that show significant

transmittance in the wavelength region of ambient temperature radiation (5 µm to 50 µm), such as certain

plastic sheets.

NOTE For multiple glazing including elements with light-scattering properties, the more detailed procedures of

ISO 15099 can be used. For daylighting calculations, procedures can be found in reference [1].

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 9845-1:1992, Solar energy — Reference solar spectral irradiance at the ground at different receiving

conditions — Part 1: Direct normal and hemispherical solar irradiance for air mass 1,5

ISO 10291:1994, Glass in building — Determination of steady-state U values (thermal transmittance) of

multiple glazing — Guarded hot plate method

ISO 10292:1994, Glass in building — Calculation of steady-state U values (thermal transmittance) of multiple

glazing

ISO 10293:1997, Glass in building — Determination of steady-state U values (thermal transmittance) of

multiple glazing — Heat flow meter method
ISO 10526:1999/CIE S005:1998, CIE standard illuminants for colorimetry
ISO/CIE 10527:1991, CIE standard colorimetric observers

CIE 13.3:1995, Technical report — Method of measuring and specifying colour rendering properties of light

source
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ISO 9050:2003(E)XX
3 Determination of characteristic parameters
3.1 General

The characteristic parameters are determined for quasi-parallel, almost normal radiation incidence. For the

measurements, the samples shall be irradiated by a beam whose axis is at an angle not exceeding 10° from

the normal to the surface. The angle between the axis and any ray of the illuminating beam shall not exceed

5° (see reference 2).
The characteristic parameters are as follows:

 the spectral transmittance  (), the spectral external reflectance  () and the spectral internal

reflectance  () in the wavelength range of 300 nm to 2 500 nm;

 the light transmittance  , the external light reflectance  and the internal light reflectance  for

v v,o v,i
illuminant D65;
 the solar direct transmittance  and the solar direct reflectance  ;
e e
 the total solar energy transmittance (solar factor) g;
 the UV-transmittance  ;
 the general colour rendering index R .

If the value of a given characteristic is required for different glass thicknesses (in the case of uncoated glass)

or for the same coating applied to different glass substrates, it may be obtained by calculation (see Annex A).

If nothing else is stated, the published characteristic parameters shall be determined using the standard

conditions given in 3.3 to 3.7. Other optional conditions given in Clause 4 shall be stated.

When calculating the characteristic parameters of multiple glazing, the spectral data of each glass component

instead of integrated data shall be used.
3.2 Performance of optical measurements

Optical measurements in transmission and reflection require special care and much experimental experience

to achieve an accuracy in transmittance and reflectance of about  0,01.

Commercial spectrophotometers (with or without integrating spheres) are affected by various sources of

inaccuracy when used for reflectance and transmittance measurements on flat glass for building.

The wavelength calibration and the photometric linearity of commercial spectrophotometers shall be checked

periodically using reference materials obtained from metrological laboratories.

The wavelength calibration shall be performed by measuring glass plates or solutions which feature relatively

sharp absorption bands at specified wavelengths; the photometric linearity shall be checked using grey filters

with a certified transmittance.

For reflectance measurements, reference materials having a reflection behaviour (i.e. reflectance level and

ratio of diffuse and direct reflectance) similar to the unknown sample shall be selected.

Thick samples (e.g. laminated glass or insulating units) can modify the optical path of the instrument’s beam

as compared to the path in air and therefore the sample beam hits an area of the detector having a different

responsivity.
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ISO 9050:2003(E)

A similar source of inaccuracy occurs in case of samples with significant wedge angles which deflect the

transmitted (and reflected) beams. It is recommended to check the reproducibility by repeating the

measurement after rotating the sample.

Additionally, in the case of reflectance measurements, glass sheets cause a lateral shear of the beam

reflected by the second surface, causing reflectance losses (whose extent is particulary evident in the case of

thick and/or wedged samples). This source of inaccuracy shall be taken into account particularly in the case of

reflectance measurements through the uncoated side. In order to quantify and correct systematic errors, it is

recommended to use calibrated reflectance standards with a thickness similar to the unknown sample.

In the case of diffusing samples (or samples with a non-negligible diffusing component or wedged samples),

transmittance and reflectance measurements shall be performed using integrating spheres whose openings

are sufficiently large to collect all the diffusely transmitted or reflected beam. The sphere diameter shall be

adequate and the internal surface adequately coated with a highly diffusing reflectance material, so that the

internal area can provide the necessary multiple reflections. Reference materials with characteristics similar to

the unknown sample as specified above shall be used.

If the transmittance or reflectance curve recorded by the spectrometer exhibits a high level of noise for some

wavelengths, the values to be considered for those wavelengths should be obtained after a smoothing of the

noise.

In this International Standard, these requirements are not all treated in detail. For more information, see

reference 3 which gives comprehensive and detailed information on how to perform optical measurements.

3.3 Light transmittance

The light transmittance  of glazing shall be calculated using the following formula:

780 nm
DV 
 
 
 380 nm
 (1)
780 nm
DV
 380 nm
where
D is the relative spectral distribution of illuminant D65 (see ISO/CIE 10526),
 () is the spectral transmittance of glazing;

V() is the spectral luminous efficiency for photopic vision defining the standard observer for photometry

(see ISO/CIE 10527);
 is the wavelength interval.

Table 1 indicates the values for D V() for wavelength intervals of 10 nm. The table has been drawn up in

such a way that D V()  1.

In the case of multiple glazing, the spectral transmittance  () shall be obtained by calculation from the

spectral characteristics of the individual components. Alternatively measurements on non-diffusing multiple

units may be performed using an integrating sphere. This may be achieved after reducing the interspaces

under conditions that allow the collection of the whole transmitted beam (see 3.2).

The calculation of the spectral transmittance  () shall be performed using methods such as algebraic

manipulation, the embedding technique of reference 4 or by recursion techniques (e.g. according to

reference 5). Any algorithm that can be shown to yield consistently the correct solution is acceptable.

© ISO 2003 — All rights reserved 3
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ISO 9050:2003(E)XX

For the calculation of  () as well as for the calculation of spectral reflectance (see 3.4), the following symbols

for the spectral transmittance and spectral reflectance of the individual components are used:

 () is the spectral transmittance of the outer (first) pane;
 () is the spectral transmittance of the second pane;

 () is the spectral transmittance of the nth (inner) pane (e.g. for triple glazing n  3);

 () is the spectral reflectance of the outer (first) pane measured in the direction of incident radiation;

 () is the spectral reflectance of the outer (first) pane measured in the opposite direction of incident

radiation;

 () is the spectral reflectance of the second pane measured in the direction of incident radiation;

 () is the spectral reflectance of the second pane measured in the opposite direction of incident

radiation;

 () is the spectral reflectance of the nth (inner) pane measured in the direction of incident radiation;

 () is the spectral reflectance of the nth (inner) pane measured in the opposite direction of incident

radiation.

For the spectral transmittance  () as a function of the spectral characteristics of the individual components of

the unit, the following formulae are obtained.
a) For double glazing:
 
   
   (2)
1
b) For triple glazing:
  
 
 
12 3
  (3)
  
11 
12 2 3 2 1 3
 

For multiple glazing with more than three components, relationships similar to Equations (2) and (3) are found

to calculate  () of such glazing from the spectral characteristics of the individual components. As these

formulae become very complex, they are not given here.

As an example for calculating  () according to the procedures of this International Standard, a glazing

composed of five components may be treated as follows:

 first consider the first three components as triple glazing and calculate the spectral characteristics of this

combination;
 next, run the same procedure for the next two components as double glazing;

 then calculate  () for the five component glazing, considering it as double glazing consisting of the

preceding triple and double glazing.
4 © ISO 2003 — All rights reserved
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ISO 9050:2003(E)
3.4 Light reflectance
3.4.1 External light reflectance of glazing

The external light reflectance of glazing  shall be calculated using the following formula:

v,o
780 nm
DV
 o 
 380 nm
  (4)
v,o
780 nm
DV
 380 nm

where  () is the spectral external reflectance of glazing, and D , V(),  and the integration procedure are

o 
as defined in 3.3

For multiple glazing, the calculation of the spectral external reflectance  () shall be performed using the

same methods as given in 3.3 for the calculation of the spectral transmittance  ().

For the spectral external reflectance  () as a function of the spectral characteristics of the individual

components of the unit, the following formulae are applied.
a) For double glazing:

 (5)
 
1 
 
b) For triple glazing:
222

  1   
      
12 2 3 1 2 3
 (6)
 
11     
      
12 2 3 2 1 3
 

For multiple glazing with more than three components, relationships similar to Equations (5) and (6) are found

to calculate  () of such glazing from the spectral characteristics of the individual components. As these

formulae become very complex, they are not given here.

As an example for calculating  (), a glazing composed of five components may be treated in the same way

as described in 3.3.
3.4.2 Internal light reflectance of glazing

The internal light reflectance of glazing  shall be calculated using the following formula:

v,i
780 nm
DV 
 
i 
 380 nm
  (7)
v,i
780 nm
DV
 
 380 nm

where  () is the spectral internal reflectance of glazing, and D V(),  and the integration procedure are

i ,
as defined in 3.3.

For multiple glazing, the calculation of the spectral internal reflectance  () shall be performed using the

same methods as given in 3.3 for the calculation of the spectral transmittance  ().

© ISO 2003 — All rights reserved 5
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ISO 9050:2003(E)XX

For the spectral internal reflectance  () as a function of the spectral characteristics of the individual

components of the unit, the following formulae are applied.
a) For double glazing:

 
  (8)
 
1 
 
b) For triple glazing:
222
1  
      
32 2 1 3 2 1

 
i3 (9)
  
11  
32 2 1 2 3 1
 

For multiple glazing with more than three components, relationships similar to Equations (8) and (9) are found

to calculate  () of such glazing from the spectral characteristics of the individual components. As these

formulae are very complex, they are not given here.

As an example for calculating  (), a glazing composed of five components may be treated in the same way

as described in 3.3.
3.5 Total solar energy transmittance (solar factor)
3.5.1 General

The total solar energy transmittance g is the sum of the solar direct transmittance  and the secondary heat

transfer factor q towards the inside (see 3.5.3 and 3.5.6), the latter resulting from heat transfer by convection

and longwave IR-radiation of that part of the incident solar radiation which has been absorbed by the glazing:

g q (10)
3.5.2 Division of incident solar radiation flux

The incident solar radiant flux per unit area  is divided into the following three parts (see Figure 1):

 the transmitted part  ;
e e
 the reflected part  ;
e e
 the absorbed part  ;
e e
where
 is the solar direct transmittance (see 3.5.3);
 is the solar direct reflectance (see 3.5.4);
 is the solar direct absorptance (see 3.5.5).
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ISO 9050:2003(E)
Key
1 outer pane
2 second inner pane
3 unit incident radiant flux
  0,38; q  0,17
e e
  0,41; q  0,04; therefore g  0,45
e i
Figure 1 — Division of the incident radiant flux for a double glazing unit
The relationship between the three characteristics is
 1 (11)
ee e

The absorbed part  is subsequently divided into two parts q and q , which are energy transferred to

e e i e e e
the inside and outside respectively:
qq (12)
ei e
where
q is the secondary heat transfer factor of the glazing towards the inside;
q is the secondary heat transfer factor of the glazing towards the outside.
3.5.3 Solar direct transmittance

The solar direct transmittance  of glazing shall be calculated using the following formula:

2500nm
S 
 300 nm
  (13)
2 500 nm
S 
 
 300 nm
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ISO 9050:2003(E)XX
where
S is the relative spectral distribution of the solar radiation;
 () is the spectral transmittance of the glazing;

 and the integration procedure are the same as in 3.3 except that the data points shall be chosen at

the wavelengths given in Table 2.

The relative spectral distribution, S , used to calculate the solar direct transmittance  , is derived from the

 e

global solar irradiance given in ISO 9845-1:1992, Table 1, column 5. The corresponding values S are given

in Table 2. This table is drawn up in such a way that  S  1.

In the case of multiple glazing, the spectral transmittance  () is calculated in accordance with 3.3.

NOTE Contrary to real situations, it is always assumed, for simplification, that the solar radiation strikes the glazing

as a beam and almost at normal incidence. In the case of oblique incidence of radiation, the solar direct transmittance of

glazing and the total solar energy transmittance are both somewhat reduced. The solar control effect becomes greater in

the case of oblique incidence of radiation.
3.5.4 Solar direct reflectance

The solar direct reflectance  of the glazing shall be calculated using the following formula:

2500nm
S 
o 
 300 nm
  (14)
2500nm
S 
 
 300 nm
where
S is the relative spectral distribution of the solar radiation (see 3.5.3);
 () is the spectral external reflectance of the glazing;

 and the integration procedure are the same as in 3.3 except that the data points shall be chosen

at the wavelengths given in Table 2.

In the case of multiple glazing, the spectral external reflectance  () is calculated in accordance with 3.4.1.

3.5.5 Solar direct absorptance
The solar direct absorptance  shall be calculated from Equation (11).
3.5.6 Secondary heat transfer factor towards the inside
3.5.6.1 Boundary conditions

For the calculation of the secondary heat transfer factor towards the inside, q , the heat transfer coefficients of

the glazing towards the outside, h , and towards the inside, h, are needed. These values mainly depend on

e i

the position of the glazing, wind velocity, inside and outside temperatures and, furthermore, on the

temperature of the two external glazing surfaces.
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ISO 9050:2003(E)

As the purpose of this International Standard is to provide basic information on the performance of glazing, the

following conventional conditions have been stated for simplicity:
 position of the glazing: vertical;

 outside surface: wind velocity approximately 4 m/s; corrected emissivity 0,837;

 inside surface: natural convection; emissivity optional;
 air spaces are unventilated.

Under these conventional, average conditions, standard values for h and h are obtained:

e i
h  23 W/(m ·K)
4,4
i 2
h3,6 W/(mK)
0,837

where  is the corrected emissivity of the inside surface [for soda lime glass,   0,837 and h  8 W/(mK)].

i i i
The corrected emissivity is defined and measured according to ISO 10292.

If other boundary conditions are used to meet special requirements they shall be stated in the test report.

Values for  lower than 0,837 (due to surface coatings with higher reflectance in the far infrared) should only

to be taken into account if condensation on the coated surface can be excluded.
3.5.6.2 Single glazing

The secondary heat transfer factor towards the inside, q, of single glazing shall be calculated using the

following formula:
q  (15)
hh
where
 is the solar direct absorptance in accordance with 3.5.2;

h , h are the heat transfer coefficients towards the outside and inside, respectively, in accordance with

e i
3.5.6.1.
3.5.6.3 Double glazing

The secondary heat transfer factor towards the inside, q, of double glazing shall be calculated using the

following formula:
 
e1 e2 e2
h 
e
q  (16)
11 1
hh 
ie
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ISO 9050:2003(E)XX
where

 is the solar direct absorptance of the outer (first) pane within the double glazing;

 is the solar direct absorptance of the second pane within the double glazing;

 is the thermal conductance between the outer surface and the innermost surface of the double

glazing (see Figure 2), in watts per square metre kelvin (W/mK);

h , h are the heat transfer coefficients towards the outside and the inside respectively in accordance

e i
with 3.5.6.1.
Key
1 pane 1
2 pane 2
3 outside
4 inside
Figure 2 — Illustration of the meaning of thermal conductance 
Characteristics  and  are calculated as follows:
e1 e2
2500nm
   
  
11 2
S
 1 
1
12
 300 nm
  (17)
2500nm
S 
 300 nm
2500nm

 
S 
 
1 
 
12
 300 nm
  (18)
2500nm
S 
 300 nm
where  (), (),  (),  (),  () are as defined in 3.3.
1 2 1 1 2
10 © ISO 2003 — All rights reserved
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ISO 9050:2003(E)

 () is the spectral direct absorptance of the outer pane, measured in the direction of the incident radiation,

given by the relationship
1  (19)
  
11 1

 () is the spectral direct absorptance of the outer pane, measured in the opposite direction to the incident

radiation, given by the relationship
 (20)
1 
11 1

 () is the spectral direct absorptance of the second pane, measured in the direction of the incident radiation,

given by the relationship
1  (21)
22 2

 and the integration procedure are the same as in 3.3 except that the data points shall be chosen at the

wavelengths given in Table 2.

The thermal conductance  shall be determined for a temperature difference of T  15 °C across the sample

and a mean temperature of the sample of 10 °C by the calculation method given in ISO 10292, or by

measuring methods using the guarded hot-plate method ISO 10291, or the heat flow meter method

ISO 10293. The recommended procedure is the calculation procedure.

If another temperature difference T across the sample and/or another mean temperature of the sample is

 to meet special requirements, this shall be stated in
used for the determination of the thermal conductance
the test report (see Clause 4).
3.5.6.4 Multiple glazing with n  2 components

The secondary heat transfer factor towards the inside, q , of a multiple glazing with more than two components

shall be calculated using the following formula:
        
e1 e2 e3 enne2 e3 e e3 en en
 
h  
e12 23 (nn1)
q  (22)
11 1 1 1
  
hh  
ie 12 23 (nn1)
where

 is the solar direct absorptance of the outer (first) pane within the n-fold glazing;

 is the solar direct absorptance of the second pane within the n-fold glazing;
 is the solar direct absorptance of the nth (inner) pane of the n-fold glazing;
h , h are the heat transfer coefficients towards the outside and towards the
...