Low Albedo Roof

For instance fresh snow reflects up to 95 of the incoming radiation.

Low albedo roof.

A 0 means no reflection. 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 sample cool roof. Therefore fresh snow has a high albedo of 95.

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. Fresh asphalt for example has an albedo of around 0 05 which means that only 5 percent of the light is reflected. Some are naturally reflective enough to achieve cool roof standards and surface treatments can transform tiles with low solar reflectance into cool roof tiles. This roof has a high albedo and reflects about 63 of the energy from sunlight.

In los angeles the average roof albedo is about 0 17. High albedo surfaces tend to keep the roof environment cooler than low albedo surfaces by producing a further contribution in energy efficiency improvement of the heat pumps due to the lower thermal gap they have to satisfy that is active cool roof effects pisello et al 2013b. This can and has led to a. The rest 95 percent is absorbed.

Tiles can be glazed to provide waterproofing or coated to provide customized colors and surface properties. On a sunny day a roof that strongly reflects sunlight can stay much cooler than a roof that absorbs sunlight. To determine the most efficient albedo level over building height profile two simulations were run with a base case of low density h w 0 3 and the other with high density h w 1 5 for albedo ranging from 0 3 to 0 8. A low albedo means a surface reflects a small amount of the incoming radiation and absorbs the rest.

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. In other words a 1 on the albedo scale means 100 percent reflection. A 1 means that a material reflects all of the light energy that hits it. By contrast water reflects about 10 of the incoming radiation resulting in a low albedo of 10.

Reflective roofs are more energy efficient and cooler inside and out. Figure 6 21 shows that when the level of albedo on walls increases the air temperature increases too. The surface temperature impacts of various albedo materials in the actual outdoor environment are studied by measuring the surface temperatures of a variety of materials tested on an actual roof. Albedo range in facade according to building density.

Deeply shadowed cavities can achieve an effective albedo approaching the zero of a black body when seen from a distance the ocean surface has a low albedo as do most forests whereas desert areas have some of the highest albedos among landforms. Tile roofs can be made of clay slate or concrete. We also generate an albedo database for several urban surfaces to serve as a reference for future use p p the results indicate that high albedo. Thermal balance of a roof under the sun.

Any albedo in visible light falls within a range of about 0 9 for fresh snow to about 0 04 for charcoal one of the darkest substances.