ASTM E1585-93

Standard Test Method for Measuring and Calculating Emittance of Architectural Flat Glass Products Using Spectrometric Measurements (Withdrawn 2002)

SCOPE
1.1 This test method covers determination of the normal and hemispherical emittance of a specular surface. This test method describes the spectrometric measurement of the near-normal specular reflectance in the mid-infrared range from 5 to at least 25 [mu]m. It includes the calculation procedures required to determine the normal and hemispherical emittance of said object.
1.2 This test method includes calibration instructions for the spectrometer and procedures for selecting reflectance-reference standards.
1.3 This test method is generally suitable for any flat, specular-reflecting specimen. It is recommended for measuring emittance of architectural glazing materials such as glass (coated and uncoated), etc. This test method is not suitable for determining the emittance of an object that is transparent in the specified range of infrared radiation.
1.4 This test method is suitable for determining the emittance of an object based on blackbody weighting at a specified temperature (typically 23°C (73°F)), as would be needed to determine the thermal performance (U-Value/ SC/SHGC) of a window assembly.
1.5 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for information only.
1.6 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.

General Information

• Status: Withdrawn
• Publication Date: 31-Dec-1992
• Withdrawal Date: 09-May-2002
• ICS: 17.180.30 - Optical measuring instruments
• ICS: 81.040.30 - Glass products
• Technical Committee: E44 - Solar, Geothermal and Other Alternative Energy Sources

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: E 1585 – 93
Standard Test Method for
Measuring and Calculating Emittance of Architectural Flat
Glass Products Using Spectrometric Measurements
This standard is issued under the fixed designation E 1585; 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 Measurement of Reflection and Transmission Properties of
Materials
1.1 This test method covers determination of the normal and
E 284 Terminology of Appearance
hemispherical emittance of a specular surface. This test method
E 932 Practice for Describing and Measuring Performance
describes the spectrometric measurement of the near-normal
of Dispersive Infrared Spectrophotometers
specular reflectance in the mid-infrared range from 5 to at least
25 μm. It includes the calculation procedures required to
3. Terminology
determine the normal and hemispherical emittance of said
3.1 Definitions:
object.
3.1.1 The definitions contained in Terminology E 284 are
1.2 This test method includes calibration instructions for the
applicable to this test method.
spectrometer and procedures for selecting reflectance-reference
3.2 Definitions of Terms Specific to This Standard:
standards.
3.2.1 blackbody—a perfect emitter and absorber of thermal
1.3 This test method is generally suitable for any flat,
radiation. A blackbody emits radiant energy at each wavelength
specular-reflecting specimen. It is recommended for measuring
at the maximum rate possible as a consequence of its tempera-
emittance of architectural glazing materials such as glass
ture and absorbs all incident radiant flux.
(coated and uncoated), etc. This test method is not suitable for
3.2.2 emissivity, E—a term reserved for the emittance for
determining the emittance of an object that is transparent in the
the restricted case of an opaque and homogeneous material.
specified range of infrared radiation.
3.2.3 emittance, e—a term that describes the ability of a
1.4 This test method is suitable for determining the emit-
body to emit radiation. It is defined as the ratio of the rate of
tance of an object based on blackbody weighting at a specified
radiant emission of the body, as a consequence of temperature
temperature (typically 23°C (73°F)), as would be needed to
only, to the corresponding emission of a perfect emitter
determine the thermal performance (U-Value/SC/SHGC) of a
(blackbody) at the same temperature.
window assembly.
3.2.4 hemispherical emittance, e — emittance of a source
h
1.5 The values stated in SI units are to be regarded as the
averaged over all the radial directions of the overspreading
standard. The inch-pound units given in parentheses are for
hemisphere.
information only.
3.2.5 normal emittance, e —emittance of a source into the
n
1.6 This standard does not purport to address all of the
direction normal to its surface.
safety concerns, if any, associated with its use. It is the
3.2.6 spectral emittance, e e —emittance based on the
n,l h,l
responsibility of the user of this standard to establish appro-
radiant energy per unit wavelength band.
priate safety and health practices and determine the applica-
3.2.7 specular reflectance—reflection in a sharply defined
bility of regulatory limitations prior to use.
direction equal to the angle of incidence from a smooth
2. Referenced Documents interface between homogeneous materials, that is, obeying the
law of reflection.
2.1 ASTM Standards:
C 1164 Practice for Evaluation of Limestone or Lime Uni-
4. Significance and Use
formity from a Single Source
4.1 The thermal performance of glazing materials utilized in
E 179 Guide for Selection of Geometric Conditions for
building facades plays a major role in the consumption and
conservation of energy. Emittance is one of the important
attributes used to calculate the thermal performance or U-value
These test methods are under the jurisdiction of ASTM Committee E44 on
of glazing materials.
Solar, Geothermal, and Other Alternative Energy Sources and is the direct
responsibility of Subcommittee E44.05 on Solar Heating and Cooling Subsystems
and Systems.
Current edition approved Dec. 15, 1993. Published March 1994. Annual Book of ASTM Standards, Vol 06.01.
2 4
Annual Book of ASTM Standards, Vol 04.01. Annual Book of ASTM Standards, Vol 03.06.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 1585
4.2 The hemispherical emittance, based on weighting with 7.1.1 Aluminum, copper, gold, and silver mirrors may all
the radiation of a blackbody at 23°C (73°F), is the accepted have a reflectance of more than 98.5 % at 10 μm. Aluminum
criterion for assessing the thermal performance of glazing coatings, however, are the least susceptible to both mechanical
assemblies. Kirchhoff’s law states that spectral emittance is and chemical degradation. Therefore, aluminum is the material
equal to spectral absorptance under equilibrium; therefore, of choice for both transfer and working standards of high
spectral absorptance may be considered to be synonymous with reflectance.
spectral emittance. Because the sum of absorptance or emit- 7.1.2 The recommended secondary (or transfer) reflectance
tance, reflectance and transmittance is equal to unity (Law of standard is an undamaged, front-surface aluminum mirror on
Energy Conservation), the reflectance of an opaque object may glass in good condition (free of surface scratches and other
also be considered equivalent to its emittance (glass is opaque contamination). Calibrate the transfer standard from 5 to $25
between 5.0 and > 50 μm). Hence, spectral emittance can be μm against a primary standard. If no calibration data is
derived from spectral reflectance data. available for a specific aluminum mirror the data given in Table
4.3 This test method recognizes that there are other uses of 1 may be used. The accuracy of a measurement using calibra-
surface emittance, for example, heat transfer during glass tion data from Table 1 is 60.5 %.
tempering, for which this test method is not applicable. 7.1.3 Working reflectance standards should be front surface
4.4 This test method is not intended for measurement of aluminum mirrors on glass from a reputable manufacturer.
substrates that are transparent to infrared radiation, such as Calibrate the working standards against the transfer standard at
certain plastics, etc. least once per month or whenever a change in the condition of
the working standard is suspected. The working standard may
5. Apparatus
have a protective overcoat of SiO, SiO,Al O , or other
2 2 3
5.1 Spectrometer and specular reflectance accessory(s) de- noninterfering material.
signed for the measurement of specular reflectance in the range
7.2 Baseline Settings/Recording—Set the baseline for the
−1 −1
of 5 (2000 cm )to $25 μm (400 cm ) at 1 μm intervals (17 reflectance scale of the spectrometer by following the instruc-
−1
cm at 25 μm).
tions provided by the instrument manufacturer. These instruc-
5.2 Spectrometer must have purge capability to eliminate tions may only cover the case of transmission and will vary
absorption due to moisture and carbon dioxide in the atmo-
sphere.
5.3 The specular reflectance accessory used for the mea-
Gold has a flatter and higher reflectance in the infrared (99 %) compared to
surement is an all-reflective optical system in which the
aluminum, but it needs to be handled with very extreme care, which makes it an
impractical choice.
calibration mirror(s) or samples(s) are located at a 1:1 optical
Calibrated primary standards are available from: National Physical Laboratory,
conjugate of the monochromator entrance slits. The angle of
Teddington, Middlesex, TW11 0LW Great Britain. The cost of calibration (at the
incidence with respect to the normal of the sample must be 10°
time of this writing, December 1992) from 5 to 55 μm is £ 580 for the first mirror
or less to minimize the effects of polarization (see Guide and £ 420 for each subsequent mirror plus the cost of the mirror. The uncertainty of
measurement is 60.3 % absolute value. The cost of NPL uncalibrated mirrors is £
E 179).
65 for an aluminum mirror, and £ 200 for an aluminum mirror with an aluminum
5.4 For double-beam spectrometers a reflectance accessory
oxide coating which can be cleaned. Calibration is also available for mirrors not
identical to the one placed in the sample beam can be placed in
supplied by NPL. At this time NIST does not have the capability to provide or
the reference beam to reduce the increased noise due to the calibrate reference mirrors in the thermal infrared. An instrument for measuring
absolute reflectivity is under development.
different path length.
6. Specimen Selection
TABLE 1 Absolute Reflectance Versus Wavelength of an Aged
A
Evaporated Aluminum Mirror
6.1 For highest precision and bias, select specimens with the
Wavelength, Absolute Wavelength, Absolute Wavelength, Absolute
following properties:
Reflectance μm Reflectance μm Reflectance
6.1.1 High material uniformity and freedom from blemishes
μm
in the area to be measured. However, blemishes observed
0.4 0.9076 1.5 0.9658 24 0.9861
under visible illumination mig
...