The specular reflected light is the light reflected from the shiny surface of a sample and diffuse reflected light is the light reflected from the rough surface of the sample. An optical device called intergrating sphere is used to measure the light reflected by the test sample. For most materials, the SRI is between 0 – 100. The total solar reflectance calculation requires taking the raw reflectance data and applying solar weighting factors for each wavelength collected. endstream endobj 237 0 obj <>/Subtype/Form/Type/XObject>>stream Up to 20 films may be entered. For non-roof materials, only solar reflectance is required. The reflection coefficient is a ratio of the amplitude of the reflected wave to the incident wave. However, for membrane materials, they shall not be too thin to be translucent. This calculator produced by Lawrence Berkeley National Labs (LBNL) allows you to compute solar reflectance index (SRI) and roof surface temperature based on solar reflectance and thermal emittance based on ASTM standard E 1980. Enter your official contact and identification details. Sure, we welcome you to visit our lab to understand our testing procedures and assess our quality system. endstream endobj 241 0 obj <>/Subtype/Form/Type/XObject>>stream The absorbed solar radiation can also be understood as dependent on the solar reflectance of the material. Y�!K��#'.V���{�TQ$aF��:7�p��v��G���W��ȅ���h�����b3��*F�*�z���_ 3&8� The reflectance varies as per the wavelength distribution of the incident radiation. H�l�� �0��L�h�h�c8����u�h�p�)�D the invisible radiation). Roofing products with high solar reflectance and thermal emittance are referred to as "Cool Roof", which refers to an outer layer or exterior surface of a roof. However, high emittance is also important. Reflectance is a fraction of electromagnetic power reflected form material or surface. Option B: use a material with the same color, but with high near-infrared reflection. The SRI calculation can be used to estimate the surface temperature of a product under prescribed conditions. However, it is troublesome to directly compare surface temperatures in material selection, as the surface temperature is dependent on many factors, such as solar radiation level and wind speed. It describes how much amount of waves can be reflected from the surface of the material or medium. 5.1 Solar reflectance and thermal emittance are important factors affecting surface and near-surface ambient air temperature. Solar Reflectance Index (SRI) 1 = 95. endstream endobj 227 0 obj <>/Subtype/Form/Type/XObject>>stream endstream endobj 232 0 obj <>/Subtype/Form/Type/XObject>>stream Solar reflectance index or solar reflectivity is the capability of a material to reflect solar energy from the surface of material back to the atmosphere. The surface temperature is determined by the following two factors: The absorbed solar radiation is dependent on the solar absorptance of the material. The equation to measure the absolute reflectance is; The reflectance is a function of the wavelength of the electromagnetic energy. Preventive Planning Framework through UV-B Resistant Material ... 25 Solar Reflectance Index (SRI) Calculation Worksheet, SRI-WS . Start a free trial now to save yourself time and money! H�2�37�402VH�*�2T0 BC3 L��2r@����������t�|]�]�$P Shown on the right is the heat transfer mechanism affecting the surface temperature under solar radiation. The SRI of a sample surface is calculated as: SRI = (temperature of the reference black surface – temperature of the sample surface) / (temperature of the reference black surface – temperature of the reference white surface) x 100. Reflectance is denoted by ρ (or p). As shown in the below figure, the light incident on a sample at an angle of θ. The instrument used by OTM for emittance measurement is Devices and Services emissometer with scaling digital voltmeter, model AE1 RD1, and small port adapter. the color we can see) and another half distributed in the near-infrared spectrum (i.e. The results in the green color box are the material properties measured in the lab: The results in the red color box are the calculated temperatures and SRI, for the medium-wind condition: Apparently, the other two columns of results in the table below are for the low-win and the high-wind conditions, respectively.