White Vs Black Roof Reflactance

They built test houses white roof vs black roof.

White vs black roof reflactance.

What they found was surface temprature hand to shingle was approximately 20 degrees warmer if black. White roofs are better than black roofs. And for that reason facility managers have been using light colored roofs for decades to keep their roof temperature low and reduce cooling costs during the hot summer months. Top 3 myths revealed.

Reflective surfaces are a form of geoengineering. 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. Single ply membranes are pre fabricated sheets rolled onto the roof and attached with mechanical fasteners adhered with chemical adhesives or held in place with ballast gravel stones or pavers. In fact city councils throughout the country are adopting model codes which favor white over black roof systems touting energy efficiencies without considering key factors that greatly contribute to the actual efficiency and life of a roof.

There s much more to selecting a roof membrane than color but it s not a black and white decision. Solar reflectivity or reflectance is the ability of a material to reflect solar energy from its surface back into the atmosphere. 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.

Incorporates both solar reflectance and thermal emissivity in a single value. Metal roofing black and white roofs metal roofing is easy to find in both black and white colors and may just be the future of roofing due to the decreasing cost of metal as a material. The most well known type of reflective surface is the cool roof. The environmental benefits of exposed membrane low slope roofing systems with high solar reflectance and thermal emittance have been established by the cool roof rating council crrc lawrence berkeley national laboratory and others.

Reflective surfaces can deliver high solar reflectance the ability to reflect the visible infrared and ultraviolet wavelengths of the sun reducing heat transfer to the surface and high thermal emittance the ability to radiate absorbed or non reflected solar energy. Solar reflectivity r solar reflectance index sri by color. Built up roofs consist of a base sheet fabric reinforcement layers and usually a dark protective. This principle is the same at work on a cool roof.

How they can be made cool. We ve heard this a lot lately. White metal has the highest rate of solar reflectivity than any other material and a large portion of california cool roofs are created with metal. However and here is the big kicker a properly ventilated attic space let me say that again properly ventilated was a 2 degree average difference.

The first being that white membranes are more durable than black membranes due to their lower surface temperature.