ASTM E972-96(R2021) pdf free download

ASTM E972-96(R2021) pdf free download.Standard Test Method for Solar Photometric Transmittance of Sheet Materials Using Sunlight
1. 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 E1175 (or Test Method E1084). 1.2 The purpose of this test method is to specify a photo- metric 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 appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.4 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
3. Terminology
3.1 Definitions—For definitions of other terms used in this test method, refer to Terminology E772. 3.1.1 illuminance, n—luminous irradiance. 3.1.2 luminous (photometric), adj—referring to a radiant (orradiometric) quantity, indicates the weighted average ofthe spectral radiometric quantity, with the photopic spectral lumi- nous efficiency function (see Annex A1) being the weighting function. 3.1.3 radiant flux, Φ = d Q/dt[Watt (W)], n— power emitted, transferred, or received in the form of electromagnetic waves or photons. See radiometric properties and quantities. 3.1.4 reflectance, ρ, Φ r /Φ i , n—the ratio of the reflected flux to the incident flux. 3.1.5 solar irradiance at a point ofa surface, E s = dΦ ⁄dA, n—the quotient of the solar flux incident on an element of a surface containing the point, by the area of that element, measured in watts per square metre. 3.1.5.1 Discussion—Measured values of transmittance and reflectance depend upon angle of incidence, solid angles of incidence and of transmission and reflection, the method of measurement of the reflected or transmitted flux, and the spectral composition of the incident flux. Because of this dependence, complete information on the technique and con- ditions of measurement should be specified. 3.1.6 solar, adj—(1) referring to a radiometric term, indi- cates that the quantity has the sun as a source or is character- istic of the sun. (2) referring to an optical property, indicates the weighted average of the spectral optical property, with the solar spectral irradiance E sλ used as the weighting function.
5. Significance and Use
5.1 Glazed apertures in buildings are generally utilized for the controlled admission of both light and solar radiant heat energy into the structure. Other devices may also be used to reflect light and solar radiant heat into a building. 5.2 The bulk of the solar radiant energy entering a building in this manner possesses wavelengths that lie from 300 to 2500 nm (3000 to 25 000 Å). Only the portion from 380 to 760 nm (3800 to 7600 Å) is visible radiation, however. In daylighting applications, it is therefore important to distinguish the radiant (solar radiant energy) transmittance or reflectance of these materials from their luminous (light) transmittance or reflec- tance. 5.3 For comparisons of the energy and illumination perfor- mances of building fenestration systems it is important that the calculation or measurement, or both, of solar radiant and luminous transmittance and reflectance of materials used in fenestration systems use the same incident solar spectral distribution. 5.4 Solar luminous transmittance and reflectance are impor- tant properties in describing the performance of components of solar illumination systems including windows, clerestories, skylights, shading and reflecting devices, and other passive fenestrations that permit the passage ofdaylight as well as solar radiant heat energy into buildings. 5.5 This test method is useful for determining the solar luminous transmittance and reflectance of optically inhomoge- neous sheet materials and diffusely reflecting materials used in natural lighting systems that are used alone or in conjunction with passive or active solar heating systems, or both. This test method provides a means of measuring solar luminous trans- mittance under fixed conditions ofincidence and viewing. This test method has been found practical for both transparent and translucent materials as well as for those with transmittances reduced by reflective coatings.