Every material can reflect light and heat to a certain extent and in a certain manner. Further, colours also have these unique properties.
Solar reflective index or SRI is a unique value that incorporates the solar reflectance and combines thermal emissivity into a single value.
SRI is extremely important as it is the main parameter used in cool roof calculations to demonstrate compliance with various environmental certifications, including LEED.
The higher the solar reflectance index, the better is the ability to reflect heat and light. Thus it is vital that in order to achieve a successful cool roof installation, a material with high SRI needs to be used.
The values for SRI of cool roofs are below
|Cool Roof requirements as per ECBC norms:
(Reflective tiles or Heat Resistant tiles) (ASTM E 1980-11, EN 673:2011 and EN 410:2011)
|abc Value||How much weathering course is required for cool roof?|
|Solar Reflectance Index||>78||96|| A building receives most of the heat through roof by radiation. Heat moves in and out of your home (or about any other structure) in four ways: by conduction (which R-Value measures), and by convection, radiation (which S.R.I value measures) and air infiltration.
Hence a minimum R value of 2.1 or 3.5 is specified by ECBC.
Combination of S.R.I and R value will give the best & everlasting terrace.
abc offers solution for R value also (T&C).
|Solar Direct Reflectance||0.70||0.77|
|Energy Conservation Building Code (section 4.3.1 & 188.8.131.52)
Bureau of Energy Efficiency
(Govt. of India, Ministry of Power)
Note: Cool Roof requirements are mandatory: Additional parameters are optional