Cool roof
From Wikipedia, the free encyclopedia
Cool roofs are an effective alternative to bulk attic insulation under roofs in humid tropical and subtropical climates. Bulk insulation can be entirely replaced by roofing systems that both reflect incident solar radiation and provide emission to the sky. Present technology is best obtained with white paint, but U.S. energy-star awards may soon be available for "cool colors" in addition to white painted roofs. Cool roof coatings function across a broader spectrum of solar radiation than white paint, especially in the infrared where the bulk of solar energy is presented. Highly emmissive and reflective cool roof painting systems are available in Australia for a material cost, epoxy primer and highbuild coolroof, so this alternative solution should not be ignored in tropical northern Australia.
Most of the roofs in the world (including over 90% of the roofs in the United States) are dark-colored. These low-reflectance surfaces reach temperatures of 150 to 190°F (66 to 88°C) and contribute to:
- Increased cooling energy use and higher utility bills;
- Higher peak electricity demand, raised electricity production costs, and a potentially overburdened power grid;
- Reduced indoor comfort;
- Increased air pollution due to the intensification of the "heat island effect"; and
- Accelerated deterioration of roofing materials, increased roof maintenance costs, and high levels of roofing waste sent to landfills.
In contrast, cool roof systems with high reflectance and emittance stay up to 70°F (39°C) cooler than traditional materials during peak summer weather. Benefits of cool roofs include reduced building heat-gain and saving on summertime air conditioning expenditures. By minimizing energy use, cool roofs do more than save money – they reduce the demand for electric power and resulting air pollution and greenhouse gas emissions.
A reflective roof coating application can dramatically reduce roof surface temperatures.
