chapter  1
32 Pages

Evolution of Cool-Roof Standards in the US

ByHashem Akbari, Ronnen Levinson

INTRODUCTION Roofs that have high solar reflectance (high ability to reflect sunlight: spectrum 0.3-2.5µm) and high thermal emittance (high ability to emit thermal radiation: spectrum 4-80µm) stay

cool in the sun. The same is true of roofs with lower thermal emittance but exceptionally high solar reflectance. Roofs that stay cool in the sun by minimizing solar absorption and maximizing thermal emission are hereafter denoted ‘cool roofs’.