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.

Sri index roof.

Solar reflectance thermal emittance and solar reflectance index sri. So just what is sri. Minimum sri for cool roof materials. Solar reflectance index sri in the early to mid 2000s legislation and regulations were established to reinforce sustainability and combat increasing problematic energy consumption.

Solar reflectivity or reflectance is the ability of a material to reflect solar energy from its surface back into the atmosphere. 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. The sr value is a number from 0 to 1 0. A value of 0 indicates that the material absorbs all solar energy and a value of 1 0 indicates total reflectance.

Solar reflective index sri is important to understand when selecting a highly reflective roof coating that will help lower energy cooling costs. For instance the standard black has a temperature increase of. Cool roofing products are classified in many cases by their solar reflectance index sri. The sri is a measure of the roof s ability to repel solar heat as shown by a small temperature increase.

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. The standard white is 100 which is most likely to reflect heat. Ref cool roof rating council solar reflectance index calculation worksheet. 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.

Sri is a unit developed by scientists at lawrence berkeley national laboratory. Solar reflectance index sri. This practice is prevalent in california. 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.

The solar reflectance index sri is a measure of the constructed surface s ability to reflect solar heat as shown by a small temperature rise. Solar reflectivity r solar reflectance index sri by color. Sri measures the roof s ability to reject solar heat defined such that a standard black reflectance 0 05 emittance 0 90 is 0 and a standard white reflectance 0 80 emittance 0 90 is 100. That s how the three terms listed above came into prominence as these measurements are how cool roofing is determined.

The sri is a calculation method using solar reflectance and thermal emittance values to determine the roof s overall capacity to refuse solar heat. What is solar reflectance index. The selection of materials with a high sri can reduce indirect solar gain in buildings and reduce the urban heat island effect.