ASTM E1980-01
(Practice)Standard Practice for Calculating Solar Reflectance Index of Horizontal and Low-Sloped Opaque Surfaces (Withdrawn 2010)
Standard Practice for Calculating Solar Reflectance Index of Horizontal and Low-Sloped Opaque Surfaces (Withdrawn 2010)
SIGNIFICANCE AND USE
Solar reflectance and thermal emittance are important factors affecting surface and near-surface ambient air temperature. Surfaces with low solar reflectance, absorb a high fraction of the incoming solar energy. A fraction of this absorbed energy is conducted into ground and buildings, a fraction is convected to air (leading to higher air temperatures), and a fraction is radiated to the sky. For equivalent conditions, the lower the emissivity of a surface the higher its steady-state temperature. Surfaces with low emissivity cannot effectively radiate to the sky and, therefore, get hot. Determination of solar reflectance and thermal emittance, and subsequent calculation of the relative temperature of the surfaces with respect to black and white reference temperature (defined as Solar Reflectance Index, SRI), may help designers and consumers to choose the proper materials to make their buildings and communities energy efficient. The method described here gives the SRI of surfaces based on measured solar reflectances and thermal emissivities of the surfaces.
SCOPE
1.1 This practice covers the calculation of the Solar Reflectance Index (SRI) of horizontal and low-sloped opaque surfaces at standard conditions. The method is intended to calculate SRI for surfaces with emissivity greater than 0.1.
1.2 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.
WITHDRAWN RATIONALE
This practice covers the calculation of the Solar Reflectance Index (SRI) of horizontal and low-sloped opaque surfaces at standard conditions. The method is intended to calculate SRI for surfaces with emissivity greater than 0.1.
Formerly under the jurisdiction of Committee D08 on Roofing and Waterproofing, this practice was withdrawn in January 2010 in accordance with section 10.5.3.1 of the Regulations Governing ASTM Technical Committees, which requires that standards shall be updated by the end of the eighth year since the last approval date.
General Information
Relations
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: E1980 – 01
Standard Practice for
Calculating Solar Reflectance Index of Horizontal and Low-
1
Sloped Opaque Surfaces
This standard is issued under the fixed designation E1980; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The steady-state surface temperature (T ) under the sun is strongly correlated to solar reflectivity
s
andthermalemissivityofthesurface.Forequivalentconditions,the T ofdarksurfaces(withlowsolar
s
reflectance) is higher than light-colored surfaces (with high solar reflectance); and surfaces with low
thermal emissivity have higher T ’s than surfaces with high thermal emissivity. The procedure
s
recommended in this standard will allow a direct comparison of T of surfaces under the sun. The
s
procedure defines a Solar Reflectance Index (SRI) that measures the relative T of a surface with
s
respect to the standard white (SRI = 100) and standard black (SRI =0) under the standard solar and
ambient conditions.
1. Scope E1918 Test Method for Measuring Solar Reflectance of
Horizontal and Low-Sloped Surfaces in the Field
1.1 This practice covers the calculation of the Solar Reflec-
tance Index (SRI) of horizontal and low-sloped opaque sur-
3. Terminology
faces at standard conditions. The method is intended to
3.1 Definitions:
calculate SRI for surfaces with emissivity greater than 0.1.
3.1.1 convective coeffıcient (h )—the rate of heat transfer
c
1.2 This standard does not purport to address all of the
fromthesurfacetoairinducedbytheairmovement,expressed
safety concerns, if any, associated with its use. It is the
–2 –1
in watts per square metre per degree Kelvin, W·m ·K .
responsibility of the user of this standard to establish appro-
3.1.2 low-sloped surfaces—surfaces with a slope smaller
priate safety and health practices and determine the applica-
than 9.5° from the horizontal.
bility of regulatory limitations prior to use.
3.1.3 reference black surface temperature (T )—is the
b
2. Referenced Documents steady-state temperature of a black surface with solar reflec-
2
tance of 0.05 and thermal emissivity of 0.9, under the standard
2.1 ASTM Standards:
solar and ambient conditions.
E408 Test Methods forTotal Normal Emittance of Surfaces
3.1.4 reference white surface temperature (T )—is the
w
Using Inspection-Meter Techniques
steady-state temperature of a white surface with solar reflec-
E772 Terminology Relating to Solar Energy Conversion
tance of 0.80 and thermal emissivity of 0.9, under the standard
E891 Tables for Terrestrial Direct Normal Solar Irradiance
3
solar and ambient conditions.
for Air Mass 1.5
3.1.5 sky temperature (T )—is the temperature of a black
E903 Test Method for Solar Absorptance, Reflectance, and sky
4
body that would radiate the same power toward the earth as
Transmittance of Materials Using Integrating Spheres
does the sky.
3.1.6 solar absorptance (a)—the fraction of solar flux
1
ThistestmethodisunderthejurisdictionofASTMCommitteeD08onRoofing
absorbed by a surface. For an opaque surface a=1−a.
and Waterproofing and is the direct responsibility of Subcommittee D08.18 on
3.1.7 solar flux (I)—is the direct and diffuse radiant power
Nonbituminous Organic Roof Coverings.
from the sun received at ground level over the solar spectrum,
Current edition approved April 10, 2001. Published April 2001. Originally
´1 –2
published as E1980–98. Last previous edition E1980–98 . DOI: 10.1520/E1980-
expressed in watts per square metre, W·m .
01.
3.1.8 solar reflectance (a)—the fraction of solar flux re-
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
flected by a surface.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
3
Withdrawn.
4
Withdrawn. The last approved version of this historical standard is referenced
on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1
---------------------- Page: 1 ----------------------
E1980 – 01
2
3.1.9 solar reflectance index (SRI)—is the relative T of a
SRI 5123.97–141.35x19.655x (4)
s
surface with respect to the standard white (SRI = 100) and
where:
standard black (SRI = 0) under the standard solar and ambient
~a–0.029´!~8.797 1 h !
c
conditions.
x5 (5)
9.5205´1 h
c
3.1.10 solar spectrum—spectral distribution of typical ter-
For a greater than 0.1, and excluding collector surfaces
restrial sunlight at air mass 1.5 as defined in Tables E891.
(surface with high solar absorptance and low thermal emit-
3.1.11 standard
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.