Sri Index Roof

The sri is a calculation method using solar reflectance and thermal emittance values to determine the roof s overall capacity to refuse solar heat.

Sri index roof.

Sri can be calculated based on the pitch of a roof its weight its solar reflectance thermal emittance and its ageing characteristics. It is defined so that a standard black surface reflectance 0 05 emittance 0 90 is 0 and a standard white surface reflectance 0 80 emittance 0 90 is 100. Solar reflectivity or reflectance is the ability of a material to reflect solar energy from its surface back into the atmosphere. So just what is sri.

Sri is a unit developed by scientists at lawrence berkeley national laboratory. The sri is a measure of the roof s ability to repel solar heat as shown by a small temperature increase. A value of 0 indicates that the material absorbs all solar energy and a value of 1 0 indicates total reflectance. Incorporates both solar reflectance and thermal emissivity in a single value.

This practice is prevalent in california. Minimum sri for cool roof materials. Cool roofing products are classified in many cases by their solar reflectance index sri. Solar reflectance index sri.

Cool asphalt roofing shingles are characterized by 3 key values. For instance the standard black has a temperature increase of. What is solar reflectance index. The sr value is a number from 0 to 1 0.

Ref cool roof rating council solar reflectance index calculation worksheet. It defines that the standard black is 0 which is most likely to absorb heat. Solar reflectance thermal emittance and solar reflectance index sri. That s how the three terms listed above came into prominence as these measurements are how cool roofing is determined.

It stands for solar reflectance index which is a combination of two numbers a material s emissivity a measure of how effectively it rejects heat and reflectivity how much light energy it bounces back. The standard white is 100 which is most likely to reflect heat. Solar reflective index sri is important to understand when selecting a highly reflective roof coating that will help lower energy cooling costs. Leed 2 2 sustainable sites credit 7 2 states that to receive one point building owners should use a roof with a solar reflective index sri of 78 over at least 75 percent of the roof s surface for roofs with slopes less than 2 12.

In many cases asphalt roofing shingle manufacturers use a shingle s third party certified aged sri value to demonstrate compliance with cool roof energy codes. Solar reflectivity r solar reflectance index sri by color. The selection of materials with a high sri can reduce indirect solar gain in buildings and reduce the urban heat island effect.