ASTM E972-96(2002)
(Test Method)Standard Test Method for Solar Photometric Transmittance of Sheet Materials Using Sunlight
Standard Test Method for Solar Photometric Transmittance of Sheet Materials Using Sunlight
SCOPE
1.1 This test method covers the measurement of solar photometric transmittance of materials in sheet form. Solar photometric transmittance is measured using a photometer (illuminance meter) in an enclosure with the sun and sky as the source of radiation. The enclosure and method of test is specified in Test Method E 1175 (or Test Method E 1084).
1.2 The purpose of this test method is to specify a photometric sensor to be used with the procedure for measuring the solar photometric transmittance of sheet materials containing inhomogeneities in their optical properties.
1.3 This standard does not purport to address all of the safety concerns, 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.
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Designation:E972–96 (Reapproved 2002)
Standard Test Method for
Solar Photometric Transmittance of Sheet Materials Using
Sunlight
This standard is issued under the fixed designation E 972; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.1 illuminance, n—luminous irradiance.
3.1.2 luminous (photometric), adj—referring to a radiant
1.1 This test method covers the measurement of solar
(or radiometric) quantity,indicatestheweightedaverageofthe
photometric transmittance of materials in sheet form. Solar
spectral radiometric quantity, with the photopic spectral lumi-
photometric transmittance is measured using a photometer
nous efficiency function (see Annex A1) being the weighting
(illuminance meter) in an enclosure with the sun and sky as the
function.
source of radiation. The enclosure and method of test is
3.1.3 radiant flux, F=d Q/dt[Watt (W)], n—power emit-
specified in Test Method E 1175 (or Test Method E 1084).
ted, transferred, or received in the form of electromagnetic
1.2 The purpose of this test method is to specify a photo-
waves or photons. See radiometric properties and quantities.
metric sensor to be used with the procedure for measuring the
3.1.4 reflectance, r, F /F, n—the ratio of the reflected flux
solar photometric transmittance of sheet materials containing r i
to the incident flux.
inhomogeneities in their optical properties.
3.1.5 solar irradiance at a point of a surface, E =dF/dA,
s
1.3 This standard does not purport to address all of the
n—the quotient of the solar flux incident on an element of a
safety concerns, if any, associated with its use. It is the
surface containing the point, by the area of that element,
responsibility of the user of this standard to establish appro-
measured in watts per square metre.
priate safety and health practices and determine the applica-
3.1.5.1 Discussion—Measured values of transmittance and
bility of regulatory limitations prior to use.
reflectance depend upon angle of incidence, solid angles of
2. Referenced Documents incidence and of transmission and reflection, the method of
measurement of the reflected or transmitted flux, and the
2.1 ASTM Standards:
spectral composition of the incident flux. Because of this
E 772 Terminology Relating to Solar Energy Conversion
dependence, complete information on the technique and con-
E 891 Tables for Terrestrial Direct Normal Solar Spectral
ditions of measurement should be specified.
Irradiance for Air Mass 1.5
3.1.6 solar, adj—(1) referring to a radiometric term, indi-
E 1084 Test Method for Solar Transmittance (Terrestrial) of
cates that the quantity has the sun as a source or is character-
Sheet Materials Using Sunlight
istic of the sun. (2) referring to an optical property, indicates
E 1175 Test Method for Determining Solar or Photopic
the weighted average of the spectral optical property, with the
Reflectance, Transmittance, and Absorptance of Materials
solar spectral irradiance E used as the weighting function.
Using a Large Diameter Integrating Sphere sl
3.1.7 spectral, adj—(1) for dimensionless optical proper-
2.2 CIE Standard:
ties, indicates that the property was evaluated at a specific
Standard Illuminant D65
wavelength, l, within a small wavelength interval, Dl about l,
3. Terminology
symbol wavelength in parentheses, as L (350 nm, 3500 Å), or
as a function of wavelength, symbol L (l). (2) for a radiomet-
3.1 Definitions—For definitions of other terms used in this
ric quantity, indicates the concentration of the quantity per unit
test method, refer to Terminology E 772.
wavelength or frequency, indicated by the subscript lambda, as
dL
L = ⁄dl, at a specific wavelength. The wavelength at which
l
These test methods are under the jurisdiction of ASTM Committee E44 on
the spectral concentration is evaluated may be indicated by the
Solar, Geothermal, and Other Alternative Energy Sources and is the direct
wavelength in parentheses following the symbol, L (350 nm).
l
responsibility of Subcommittee E44.05 on Solar Heating and Cooling Subsystems
3.1.8 transmittance, t = F /F, n—the ratio of the transmit-
and Systems. t i
Current edition approved April 10, 1996. Published May 1996. Originally ted flux to the incident radiant flux.
published as E 972 – 83. Last previous edition E 972 – 88 (1992).
Annual Book of ASTM Standards, Vol 12.02.
Available from Commission Internationale de l’Eclairage (International Com-
mission on Illumination), Barean Central de la CIE, 4 Av. du Recteur Poincaré,
75-Paris, France.
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959, United States.
E972
4. Summary of Test Method exception that the sensing element shall be replaced by the
sensing element described by this test method.
4.1 Using sunlight as the source and a photometer as the
6.1.1 The sensing element of this instrument shall be a
detector, the specimen is made to be the cover of an enclosure
photometer (illuminance meter) consisting of a suitable radia-
with the plane of the specimen normal to the direct component
tion detector (such as a silicon photovoltaic device), a filter,
of the incident solar radiation. Luminous transmittance is
and a diffusing element. The filter shall be designed so that the
measured as the ratio of the transmitted illuminance to the
spectral response of the photometer very closely matches that
incident illuminance.
of the standard human observer, as specified by the C.I.E.
photopic spectral luminous efficiency function tabulated in
5. Significance and Use
Annex A1. The response of the photometer at wavelength l,
5.1 Glazed apertures in buildings are generally utilized for
divided by its response at 555 nm (5550 Å), shall depart from
the controlled admission of both light and solar radiant heat
the spectral luminous efficiency of the standard human ob-
energy into the structure. Other devices may also be used to
server at wavelength l by no more than 2 % for all wave-
reflect light and solar radiant heat into a building.
lengths from 390 to 750 nm (3900 to 7500 Å). Photometer
5.2 The bulk of the solar radiant energy entering a building
response shall be essentially zero outside this range.
in this manner possesses wavelengths that lie from 300 to 2500
6.1.2 Cosine Response —Theresponseofthephotometerto
nm (3000 to 25 000 Å). Only the portion from 380 to 760 nm
uniform, collimated incident radiation at an angle u of inci-
(3800 to 7600 Å) is visible radiation, however. In daylighting
dence, divided by its response at normal incidence (u = 0°),
applications, it is therefore important to distinguish the radiant
shall depart from the cosine of u by no more than (u4 18) %,
(solar radiant energy) transmittance or reflectance of these
with u in deg.
materials from their luminous (light) transmittance or reflec-
6.1.3 The diffusing element and detector electronics shall be
tance.
designed so that the voltage (or current) output of the sensor is
5.3 For comparisons of the energy and illumination perfor-
proportionaltohemisphericalilluminanceincidentuponit.The
mances of building fenestration systems it is important that the
photometer shall be located inside the box so that its entrance
calculation or measurement, or both, of solar radiant and
aperture (the diffusing element) is centered approximately 50
luminous transmittance and reflectance of materials used in
mm (2 in.) below the plane of the rim of the box. Other
fenestration systems use the same incident solar spectral
instructions shall be closely followed.
distribution.
5.4 Solar luminous transmittance and reflectance are impor- 7. Test Specimens
tant properties in descri
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