The science behind a “cool” reflective roof is simple: Light colors reflect solar radiation and dark colors absorb solar radiation. Reflective roofs may reduce the cooling costs associated with commercial buildings and residences by reflecting photons emitted by the sun back into the environment. “Coolness” is measured by two properties: solar reflectance (SR, or reflectivity) and thermal emittance (emissivity), or a combination of the two, which is called Solar Reflectance Index (SRI). These are the terms one will run into when talking about a cool roof.
When making the decision to choose a cool roof, there are certain questions that the homeowner, or building owner, need to address: