ASTM E1175 is a standard test method for determining the absolute total solar or photopic reflectance, transmittance, or absorptance of materials or surfaces. Conventional test parameters apply only to flat, homogeneous, isotropic structures and do not work for non-uniform surfaces. This protocol provides a clear testing structure to reliably assess nonhomogeneous, textured, patterned, or proportionally different articles without repeatedly performing multi-point experimental readings.
The scope of ASTM E1175 includes:
- Materials: Nonhomogeneous, patterned, textured, corrugated, specular, diffuse, opaque, and semitransparent specimens.
- Purpose: Optical values of nonhomogeneous materials are not uniform, so an appropriate technique is needed to measure them reliably.
- Properties measured: Absolute total solar reflectance, photopic reflectance, solar transmittance, photopic transmittance, and solar absorptance.
- Methods: Use of a specially designed large-diameter integrating sphere for dealing with large radiation beams.
- Result: Absolute numerical values of directional-hemispherical reflectance, transmittance, and calculated absorptance values.
- Test Limitation: Only very special specimen shapes and configurations can be accommodated with a large-diameter integrating sphere.
- Environmental Conditions: Standardized laboratory conditions with terrestrial spectrum standard solar radiation or the photopic vision response curve.
- Applications: Commercial Shading Devices, Draperies, Woven Woods, Corrugated Plastics, and Textured Solar Collectors.
What are the Uses of ASTM E1175 Testing?
This standard is used in industrial material analysis to calculate solar performance ratings for materials that reflect or absorb solar energy unevenly. This process ensures building materials meet performance requirements under natural sunlight. This standard,
- Enables designers to precisely measure the solar heat gain coefficient of composite window treatments.
- Provides a basis for engineering groups to consider solar absorptance of corrugated roofing material.
- Allows the manufacturers to validate the industrial plastic barriers’ photopic transparency profiles.
- Provides laboratories with the ability to provide repeatable optical information on non-standard parts.
What material can be tested under ASTM E1175?
Testing is directly applicable to the nonhomogeneous, nonisotropic, corrugated, patterned, or textured profile of complex materials. Typical materials include woven wood panels, thick drapes, patterned architectural glass, corrugated polymers, louvered windows, and a solar collector surface with mixed specular/diffuse scattering properties. Current spectrophotometers cannot accurately measure these irregular surfaces because the light is severely dispersed and the surface profile varies across the area. With a wider testing beam pathway over a large integrating area, the overall optical properties of these irregular materials, whether they are partially transparent or completely opaque, are fully captured and averaged into a single valid data determination.
Why is ASTM E1175 Important?
This standard matters because conventional optical evaluation devices cannot accurately capture the properties of textured or uneven materials and therefore cannot accurately calculate energy consumption. This standard establishes an explicit methodology that uses large integrating spheres, removing measurement variations caused by structural patterns and component corrugation. It gives developers, architects, and environmental compliance agencies reliable information on the characteristics of solar heat transmission and light reflection. In the end, this precise data helps optimize building energy management systems, remains compliant with current green building standards, and avoids unforeseen thermal issues in unique structural endeavors.
