The "ASTM E1980-11 Standard Procedure for Calculating the Solar Reflectance Index of Horizontal and Low-Slope Opaque Surfaces," developed by the American Society for Testing and Materials (ASTM) , describes a procedure for calculating the Solar Reflectance Index (SRI) of horizontal and low-slope opaque surfaces under standard conditions . This procedure aims to calculate the solar reflectance index for surfaces with emissivity greater than 0,1.
Solar reflection and thermal dissipation are important factors affecting surface and near-surface ambient air temperature. Surfaces with low solar reflectance absorb a high fraction of incoming solar energy. Some of this absorbed energy is transmitted to the ground and buildings, some is carried into the air and leads to higher air temperatures, and some is radiated into the sky. For equivalent conditions, the lower the emissivity of a surface, the higher its steady-state temperature. Surfaces with low emissions cannot radiate effectively into the sky and therefore become warmer.
Determining the solar reflectance and thermal emission and then calculating the relative temperature of the surfaces relative to the black and white reference temperature is defined as the solar reflectance index. This value helps designers and consumers choose appropriate materials to make their buildings and communities energy efficient.
There is an increasing need to know the solar reflectance index of materials used for roofing. Especially for buildings in warm and hot climates where the main energy issue is cooling control rather than heating control. The solar reflectance index is determined from the sunlight reflection and thermal emissivity of a material.
Temperatures of opaque surfaces exposed to solar radiation are generally higher than adjacent air temperatures. In the case of roofs or walls surrounding conditioned areas, increased inward heat flow occurs. The extent to which solar radiation affects surface temperatures depends on the sunlight reflectance of the exposed surface.
A solar reflectance of 1,0 (100 percent reflected) means no effect on surface temperature, while a solar reflectance of 0 (none reflected, all absorbed) results in maximum impact.
For painted materials, both solar reflection and emissivity properties are a function of the type of paint system used as well as the pigments used to achieve the color. In some cases, solar reflectance index data for the paint system is available from paint manufacturers.
However, even matching colors may have different solar reflectance index values if sourced from different manufacturers. Any custom matching color will require special testing.
Our organization, with its trained and expert staff and advanced technological equipment, among the numerous testing, measurement, analysis and evaluation studies it carries out for businesses in various sectors, provides the following solutions defined in the "ASTM E1980-11 Standard practice for calculating the solar reflection index of horizontal and low-slope opaque surfaces" standard. It also provides testing services.
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