Understanding Cool Roofs

Highly infrared emissive and solar reflective roofing surfaces can help save money in air-conditioning costs because less heat is transferred into the building. Increased insulation can also mitigate this heat transfer. This translates into less cooling to keep people comfortable. This is especially true on hot afternoons in peak energy periods, such as 3 p.m. in the middle of July on a 90ºF day. Lower peak usage helps to reduce the chance of rolling power outages, which means businesses stay up and running

The Role of Reflectivity and Emissivity in Cool Roofs

In order to help better understand the concept of cool roofs, we need to understand reflectivity and emissivity. Energy efficient material selection will impact indoor environmental comfort, which results in lower energy consumption and reduced demand during peak periods. Highly reflective and highly emissive products, such as the white membrane, combined with the proper amount of roof insulation, offers a system that significantly reduces heat gain into the building.

Reflectivity
Solar reflectivity (or reflectance) is the fraction of the solar energy that is reflected by the surface (i.e., roofing membrane) back to the sky. White membranes have the highest solar reflectivity, while black have the lowest.

Emissivity