Roof Albedo Definition

Albedo is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0 corresponding to a black body that absorbs all incident radiation to 1 corresponding to a body that reflects all incident radiation.

Roof albedo definition.

Because they can reduce surface temperatures by up to 80 f about 45 c these products also have a big impact on cooling costs. A perfect reflector would have an albedo of 1 whereas a perfect absorber would have an albedo of 0. The words albedo or solar reflectance and emittance are words that relate to energy efficiency in a roof system. The term albedo describes the proportion of incident radiation reflected by a system.

Albedo is the reflecting power of a surface. The albedo of a surface is a measure of its reflectivity to solar radiation paterson 1994. In the project definition the albedo values can be adjusted each month in order to take any possible snow cover into consideration. By preventing a majority of the heat from ever reaching the surface these roofs work to greatly reduce hvac cooling costs during the summer months.

Solar reflectance is an important characteristic in roofing as warmer climates will require the use of materials that have high reflectance so that the home will stay cool and and absorb as little heat as possible. Fresh snow has a particularly high albedo. Reflective roof coatings also known as albedo coatings are products applied to roofs to reduce solar heat especially in areas with hot sunny weather for a good part of the year. 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.

Hence the average albedo of the planet dictates the levels of solar radiation held and reflected at its surface. Epa energy star specifies an albedo of 0 65 or higher for low slope roof applications and 0 25 for sloped roofs most roofing industry experts agree that a cool roof is one the exhibits a combination of high reflectivity and high emissivity leed version 2 2 released in october 2005 is the first national specification to use a relatively. Lighter materials such as white clothing and light colored houses reflect more heat than they absorb and will have an albedo nearer to 1. The albedo effect has been proven in both natural and man made environments in recent years.

The usual value is 0 2 default in pvsyst. Albedo is sometimes used to describe the proportion of solar radiation reflected by the earth back into space and this reflectance of solar radiation is also. The value usually admitted in the urban localities is of the order of 0 14 to 0 22 and can go up till 0 8 for a snow cover. Most roof manufacturers have total reflectance and thermal emittance values listed for their various roofing colors and finishes.

The proportion reflected is not only determined by properties of the surface itself but also by the spectral and angular distribution of so.