ASTM E424-71(2015)

Standard Test Methods for Solar Energy Transmittance and Reflectance (Terrestrial) of Sheet Materials

SIGNIFICANCE AND USE
5.1 Solar-energy transmittance and reflectance are important factors in the heat admission through fenestration, most commonly through glass or plastics. (See Appendix X3.) These methods provide a means of measuring these factors under fixed conditions of incidence and viewing. While the data may be of assistance to designers in the selection and specification of glazing materials, the solar-energy transmittance and reflectance are not sufficient to define the rate of heat transfer without information on other important factors. The methods have been found practical for both transparent and translucent materials as well as for those with transmittances reduced by highly reflective coatings. Method B is particularly suitable for the measurement of transmittance of inhomogeneous, patterned, or corrugated materials since the transmittance is averaged over a large area.
SCOPE
1.1 These test methods cover the measurement of solar energy transmittance and reflectance (terrestrial) of materials in sheet form. Method A, using a spectrophotometer, is applicable for both transmittance and reflectance and is the referee method. Method B is applicable only for measurement of transmittance using a pyranometer in an enclosure and the sun as the energy source. Specimens for Method A are limited in size by the geometry of the spectrophotometer while Method B requires a specimen 0.61 m2 (2 ft2). For the materials studied by the drafting task group, both test methods give essentially equivalent results.  
1.2 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Oct-2015
• ICS: 81.040.20 - Glass in building
• ICS: 81.040.30 - Glass products
• Technical Committee: E44 - Solar, Geothermal and Other Alternative Energy Sources
• Drafting Committee: E44.20 - Optical Materials for Solar Applications

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E424 − 71 (Reapproved 2015)
Standard Test Methods for
Solar Energy Transmittance and Reflectance (Terrestrial) of
1
Sheet Materials
This standard is issued under the fixed designation E424; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope E308 Practice for Computing the Colors of Objects by Using
the CIE System
1.1 These test methods cover the measurement of solar
energy transmittance and reflectance (terrestrial) of materials in
3. Definitions
sheet form. Method A, using a spectrophotometer, is applicable
for both transmittance and reflectance and is the referee
3.1 solar absorptance—the ratio of absorbed to incident
method. Method B is applicable only for measurement of
radiant solar energy (equal to unity minus the reflectance and
transmittance using a pyranometer in an enclosure and the sun
transmittance).
as the energy source. Specimens for Method A are limited in
3.2 solar admittance—solar heat transfer taking into ac-
size by the geometry of the spectrophotometer while Method B
2 2
count reradiated and convected energy.
requires a specimen 0.61 m (2 ft ). For the materials studied
by the drafting task group, both test methods give essentially
3.3 solar energy—for these methods the direct radiation
equivalent results.
from the sun at sea level over the solar spectrum as defined in
1.2 This standard does not purport to address all of the
3.2, its intensity being expressed in watts per unit area.
safety concerns, if any, associated with its use. It is the
3.4 solar reflectance—the percent of solar radiation (watts/
responsibility of the user of this standard to establish appro-
unit area) reflected by a material.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
3.5 solar spectrum—for the purposes of these methods the
1.3 This international standard was developed in accor-
solar spectrum at sea level extending from 350 to 2500 nm.
dance with internationally recognized principles on standard-
3.6 solar transmittance—the percent of solar radiation
ization established in the Decision on Principles for the
(watts/unit area) transmitted by a material.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
4. Summary of Methods
Barriers to Trade (TBT) Committee.
4.1 Method A—Measurements of spectral transmittance, or
2. Referenced Documents
reflectance versus a magnesium oxide standard, are made using
2
2.1 ASTM Standards:
an integrating sphere spectrophotometer over the spectral range
E259 Practice for Preparation of Pressed Powder White
from 350 to 2500 nm. The illumination and viewing mode shall
Reflectance Factor Transfer Standards for Hemispherical
be normal-diffuse or diffuse-normal. The solar energy trans-
and Bi-Directional Geometries
mitted or reflected is obtained by integrating over a standard
E275 Practice for Describing and Measuring Performance of
solar energy distribution curve using weighted or selected
Ultraviolet and Visible Spectrophotometers
ordinates for the appropriate solar-energy distribution. The
distribution at sea level, air mass 2, is used.
1
These test methods are under the jurisdiction of ASTM Committee E44 on 4.2 Method B—Using the sun as the source and a pyranom-
Solar, Geothermal and Other Alternative Energy Sources and is the direct respon-
eter as a detector the specimen is made the cover of an
sibility of Subcommittee E44.20 on Optical Materials for Solar Applications.
enclosure with the plane of the specimen perpendicular to the
Current edition approved Nov. 1, 2015. Published November 2015. Originally
incident radiation; transmittance is measured as the ratio of the
approved in 1971. Last previous edition approved in 2007 as E424 – 71 (2007).
DOI: 10.1520/E0424-71R15.
energy transmitted to the incident energy. (The apparatus of
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Method B has been used for the measurement of solar-energy
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
reflectance but there is insufficient experience with this tech-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. nique for standardization at present.)
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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E424 − 71 (2015)
5.
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E424 − 71 (Reapproved 2007) E424 − 71 (Reapproved 2015)
Standard Test Methods for
Solar Energy Transmittance and Reflectance (Terrestrial) of
1
Sheet Materials
This standard is issued under the fixed designation E424; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope
1.1 These test methods cover the measurement of solar energy transmittance and reflectance (terrestrial) of materials in sheet
form. Method A, using a spectrophotometer, is applicable for both transmittance and reflectance and is the referee method. Method
B is applicable only for measurement of transmittance using a pyranometer in an enclosure and the sun as the energy source.
Specimens for Method A are limited in size by the geometry of the spectrophotometer while Method B requires a specimen 0.61
2 2
m (2 ft ). For the materials studied by the drafting task group, both test methods give essentially equivalent results.
1.2 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
E259 Practice for Preparation of Pressed Powder White Reflectance Factor Transfer Standards for Hemispherical and
Bi-Directional Geometries
E275 Practice for Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers
E308 Practice for Computing the Colors of Objects by Using the CIE System
3. Definitions
3.1 solar absorptance—the ratio of absorbed to incident radiant solar energy (equal to unity minus the reflectance and
transmittance).
3.2 solar admittance—solar heat transfer taking into account reradiated and convected energy.
3.3 solar energy—for these methods the direct radiation from the sun at sea level over the solar spectrum as defined in 3.2, its
intensity being expressed in watts per unit area.
3.4 solar reflectance—the percent of solar radiation (watts/unit area) reflected by a material.
3.5 solar spectrum—for the purposes of these methods the solar spectrum at sea level extending from 350 to 2500 nm.
3.6 solar transmittance—the percent of solar radiation (watts/unit area) transmitted by a material.
4. Summary of Methods
4.1 Method A—Measurements of spectral transmittance, or reflectance versus a magnesium oxide standard, are made using an
integrating sphere spectrophotometer over the spectral range from 350 to 2500 nm. The illumination and viewing mode shall be
normal-diffuse or diffuse-normal. The solar energy transmitted or reflected is obtained by integrating over a standard solar energy
distribution curve using weighted or selected ordinates for the appropriate solar-energy distribution. The distribution at sea level,
air mass 2, is used.
1
These test methods are under the jurisdiction of ASTM Committee E44 on Solar, Geothermal and Other Alternative Energy Sources and is the direct responsibility of
Subcommittee E44.05 on Solar Heating and Cooling Systems and Materials.
Current edition approved March 1, 2007Nov. 1, 2015. Published April 2007November 2015. Originally approved in 1971. Last previous edition approved in 20012007
as E424-71(2001).E424-71(2007). DOI: 10.1520/E0424-71R07.10.1520/E0424-71R15.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
E424 − 71 (2015)
4.2 Method B—Using the sun as the source and a pyranometer as a detector the specimen is made the cover of an enclosure
with the plane of the specimen perpendicular to the incident radiation; transmittance is measured as the ratio of the energy
transmitted to the incident energy. (The apparatus of Method B has been used for the measurement of solar-energy reflectance but
there is insufficient experience with this technique for standardization at present.)
5.
...