Thermal Emittance Metal Roof

In the case of a cool metal roof a lower surface temperature translates into less heat gain into the attic space or living space below the roof.

Thermal emittance metal roof. Recycled content of berridge metal. For every 10 increase in roof reflectance heating cooling costs drop 2 cents per square foot per year. Heat is absorbed but not released. Roof thermal emittance measures the surface s ability to radiate any absorbed solar energy.

Sri measures the roof s ability to reject solar heat defined such that a standard black reflectance 0 05 emittance 0 90 is 0 and a standard white reflectance 0 80 emittance 0 90 is 100. The thermal emittance of many materials whether wood paper plaster rubber water ice marble paint clay or concrete is very high of the order 0 90. For every 1 increment in roof reflectance the surface temperature of the metal roof decreases 1 degree fahrenheit. Thermal emittance refers to the ability of a material to radiate the heat that it absorbs.

The use of area weighted averages to comply with these requirements shall be permitted. With the exception of a metallic surface most roofing materials can have emittance values above 0 85 85. However shiny bare and acrylic coated metals have a low thermal emittance and when used as a roof cover stay warmer than does a thermoplastic or painted metal roof. For example a metal roof which gets so hot in the sun that it burns to the touch has a low thermal emittance.

Scientists use a number between 0 and 1 or 0 and 100 to express emittance. Aged solar reflectance tested in accordance with astm c 1549 astm e 903 or. Incorporates both solar reflectance and thermal emissivity in a single value. A cool metal roof with high solar reflectance and high thermal emittance would have a lower surface temperature as compared to a roof with low reflectance and low emittance.

Effectiveness of cool roof coatings with ceramic particles cool roofs coating ceramic particles solar reflectance thermal emittance thermal conductivity abstract liquid applied coatings promoted as cool roof coatings including proceedings of the 2011 international roofing symposium 8 epdm 0 876 e metal 0 814 0 83 0 81 epdm 0 814 table. Ideally you ll want a roof that has equal reflectance and emittance because they complement one another. A surface with a high thermal emittance will both absorb heat and radiate back into the environment. The result is a cooler.

Materials lacking 3 year aged tested values for either solar reflectance or thermal emittance shall be assigned both a 3 year aged solar reflectance in accordance with section c402 3 1 and a 3 year aged thermal emittance of 0 90. One example is a metal wrench left. Thermal emittance is the specific term you should look for when shopping for a new roof. The higher their thermal emittance is the more rapidly roofs can cool ashrae 2011.