ASTM E1918-06

Standard Test Method for Measuring Solar Reflectance of Horizontal and Low-Sloped Surfaces in the Field

SIGNIFICANCE AND USE
Solar reflectance is an important factor affecting surface and near-surface ambient air temperature. Surfaces with low solar reflectance (typically 30 % or lower), absorb a high fraction of the incoming solar energy which is either conducted into buildings or convected to air (leading to higher air temperatures). Use of materials with high solar reflectance may result in lower air-conditioning energy use and cooler cities and communities. The test method described here measures the solar reflectance of surfaces in the field.
SCOPE
1.1 This test method covers the measurement of solar reflectance of various horizontal and low-sloped surfaces and materials in the field, using a pyranometer. The test method is intended for use when the sun angle to the normal from a surface is less than 45.

General Information

• Status: Historical
• Publication Date: 14-Aug-2006
• ICS: 17.180.20 - Colours and measurement of light
• Technical Committee: D08 - Roofing and Waterproofing
• Drafting Committee: D08.18 - Nonbituminous Organic Roof Coverings

Relations

• Replaces: ASTM E1918-97 - Standard Test Method for Measuring Solar Reflectance of Horizontal and Low-Sloped Surfaces in the Field (Withdrawn 2006)
• Effective Date: 15-Aug-2006
• Replaced By: ASTM E1918-06(2015) - Standard Test Method for Measuring Solar Reflectance of Horizontal and Low-Sloped Surfaces in the Field
• Effective Date: 01-Feb-2015
• Referred By: ASTM D3794-22 - Standard Guide for Testing Coil Coatings
• Effective Date: 15-Aug-2006
• Referred By: ASTM E631-15 - Standard Terminology of Building Constructions
• Effective Date: 15-Aug-2006

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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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:E1918 −06
StandardTest Method for
Measuring Solar Reflectance of Horizontal and Low-Sloped
1
Surfaces in the Field
This standard is issued under the fixed designation E1918; 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.
1. Scope 3.1.5 solar reflectance—the fraction of solar flux reflected
by a surface.
1.1 This test method covers the measurement of solar
reflectance of various horizontal and low-sloped surfaces and 3.2 Definitions of Terms Specific to This Standard:
materials in the field, using a pyranometer. The test method is 3.2.1 solar spectrum—the solar spectrum at ground level
intended for use when the sun angle to the normal from a extending from wavelength 0.3 to 3.5 µm.
surface is less than 45°.
4. Summary of Test Method
2. Referenced Documents
4.1 A pyranometer is used to measure incoming and re-
2
2.1 ASTM Standards:
flected solar radiation for a uniform horizontal or low-sloped
E722 PracticeforCharacterizingNeutronFluenceSpectrain
surface. The solar reflectance is the ratio of the reflected
Terms of an Equivalent Monoenergetic Neutron Fluence
radiation to the incoming radiation.
for Radiation-Hardness Testing of Electronics
E903 Test Method for Solar Absorptance, Reflectance, and 5. Significance and Use
Transmittance of Materials Using Integrating Spheres
5.1 Solar reflectance is an important factor affecting surface
3
(Withdrawn 2005)
and near-surface ambient air temperature. Surfaces with low
solar reflectance (typically 30 % or lower), absorb a high
3. Terminology
fractionoftheincomingsolarenergywhichiseitherconducted
3.1 Definitions:
into buildings or convected to air (leading to higher air
3.1.1 low-sloped surfaces—surfaces with a slope smaller
temperatures).Useofmaterialswithhighsolarreflectancemay
than 9.5°. The roofing industry has widely accepted a slope of
result in lower air-conditioning energy use and cooler cities
2:12 or less as a definition of low-sloped roofs. This corre-
and communities.The test method described here measures the
sponds to a slop of approximately 9.5° (16.7 %).
solar reflectance of surfaces in the field.
3.1.2 pyranometer—an instrument (radiometer) used to
measure the total solar radiant energy incident upon a surface 6. Apparatus
per unit time and unit surface area.
6.1 Sensor—A precision spectral pyranometer (PSP) sensi-
3.1.3 solar energy—the radiant energy originating from the
tive to radiant energy in the 0.28–2.8 µm band is recom-
sun. Approximately 99 % of solar energy lies between wave-
mended. A typical pyranometer yields a linear output of
–2
lengths of 0.3 to 3.5 µm.
60.5 % between 0 and 1400W·m and a response time of one
s. Specific characteristics can be obtained based on calibration
3.1.4 solar flux—for these measurements, the direct and
by the manufacturer of the pyranometer. Other suitable pyra-
diffuse radiation from the sun received at ground level over the
4
nometers are discussed in Zerlaut. The double-dome design of
solar spectrum, expressed in watts per square metre.
the PSP minimizes the effects of internal convection resulting
fromtiltingthepyranometeratdifferentangles.Forthisreason,
1
This test method is under the jurisdiction ofASTM Committee D08 on Roofing
the PSP is especially suitable for this test, since measurement
and Waterproofing and is the direct responsibility of Subcommittee D08.18 on
Nonbituminous Organic Roof Coverings.
of solar reflectivity requires the apparatus to alternatively face
Current edition approved Aug. 15, 2006. Published September 2006. Originally
up and down.
approvedin1997.Lastpreviouseditionapprovedin1997asE1918 – 97,whichwas
withdrawn in January 2006 and reinstated inAugust 2006. DOI: 10.1520/E1918-06.
6.2 Read-Out Instrument—Theanalogoutputfromthepyra-
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
nometer is converted to digital output with a readout meter
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.
4
3
The last approved version of this historical standard is referenced on Zerlaut, G., “Solar Radiation Instrumentation,” Solar Resources, R.L.
www.astm.org. Hulstrom, ed., MIT Press, Cambridge, MA, 1989, pp. 173–308.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
E1918−06
(such as EPLAB Model 455 Instantaneous Solar Radiation betweenthehoursof9a.m.and3p.m.localstandardtime;this
Meter) that has an accuracy of better than 60.5 % and
...