Roof Albedo Definition

Standard or dark roofs can reach temperatures of 150 f or more in the summer sun.

Roof albedo definition.

Cool roofs can be made of a highly reflective type of paint a sheet covering or highly reflective tiles or shingles. The former also called normal reflectance is a measure of a surface s relative brightness when illuminated and observed vertically. Investigators frequently rely on observations of normal albedo to determine. The normal albedo of snow for example is nearly 1 0 whereas that of charcoal is about 0 04.

These values usually are listed in decimals with 0 99 being the best and 0 000 being the worst. Normal albedo and bond albedo. Something that appears white reflects most of the light that hits it and has a high albedo while something that looks dark absorbs most of the light that hits it indicating a low albedo. The proportion reflected is not only determined by properties of the surface itself but also by the spectral and angular distribution of so.

Albedo in the built environment the term albedo describes the proportion of incident radiation reflected by a system. A high thermal emittance also plays a role particularly in climates that are warm and sunny. A high solar reflectance or albedo is the most important characteristic of a cool roof as it helps to reflect sunlight and heat away from a building reducing roof temperatures. One of the more recent advancements in the field of green commercial construction are what are known as cool or albedo roofs.

In los angeles the average roof albedo is about 0 17. A cool roof under the same conditions could stay more than 50 f cooler and save energy and money by using less air conditioning. It is measured on a scale of 0 to 1 where higher numbers indicate greater reflectance. Most roof manufacturers have total reflectance and thermal emittance values listed for their various roofing colors and finishes.

Albedo is the fraction of sunlight that is reflected from a surface. In contrast to conventional roofs these kind are specifically designed to reduce internal building temperature by reflecting the sun s uv rays. As one would expect albedo roofs are formulated with special high eminence materials that keep project a high level of thermal energy back into the atmosphere. A perfect reflector would have an albedo of 1 whereas a perfect absorber would have an albedo of 0.

Albedo al bee doh is a measure of how much light that hits a surface is reflected without being absorbed. Albedo is usually differentiated into two general types. Reflective roofs are more energy efficient and cooler inside and out. Surface albedo is defined as the ratio of radiosity to the irradiance received by a surface.

A sample cool roof.