High Albedo Roof

In los angeles the average roof albedo is about 0 17.

High albedo roof.

In this view those coatings are usually applied over flat and low sloped roofs in general in order to avoid summer overheating. A sample cool roof this roof has a high albedo and reflects about 63 of the energy from sunlight. 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. In the morning and in the late afternoon the high albedo materials were as cool as the air itself.

Over the past three decades high albedo roofing has been promoted as a strategy to mitigate the urban heat island effect and reduce cooling energy demand and costs. A cool roof is one that has been designed to reflect more sunlight and absorb less heat than a standard roof. This implies that not only is cost of space heating increased but greenhouse gas production from combustion is driven up as well potentially exacerbating urban heat island effects. The specification of a high albedo roof may result in a requirement for added heating which otherwise would have been gathered passively through the roof.

High albedo coatings as previously mentioned are able to limit the increase of surface temperature of a roof in opposition to a high absorptive finishing. This criterion can also be met by installing a vegetated roof for at least 50 of the roof area or installing a high albedo and vegetated roof in combination that meets this formula. 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. Nearly any type of building can benefit from a cool roof but consider the climate and other factors before deciding.

On clear sunny days when the solar noon surface temperatures of conventional roofing materials were about 40 degrees c 72 degrees f warmer than air the surface temperature of high albedo coatings were only about 5degreesc warmer than air. A high thermal emittance also plays a role particularly in climates that are warm and sunny. In addition high albedo roofs can increase thermal comfort in non conditioned buildings. Cool roofs can be made of a highly reflective type of paint a sheet covering or highly reflective tiles or shingles.