High Albedo Roof

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.

High albedo roof.

Nearly any type of building can benefit from a cool roof but consider the climate and other factors before deciding. A high thermal emittance also plays a role particularly in climates that are warm and sunny. 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. A sample cool roof this roof has a high albedo and reflects about 63 of the energy from sunlight.

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. 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. In this view those coatings are usually applied over flat and low sloped roofs in general in order to avoid summer overheating. 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.

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. In the morning and in the late afternoon the high albedo materials were as cool as the air itself. 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. Area of roof meeting minimum sri roof 0 75 area of vegetated roof 0 5 total roof area.

In los angeles the average roof albedo is about 0 17. 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. On a sunny day a roof that strongly reflects sunlight can stay much cooler than a roof that absorbs sunlight. In addition high albedo roofs can increase thermal comfort in non conditioned buildings.