Cool Roofs for Buildings | US EPA

Cool roofs are innovative roof system that reflects sunlight and absorb less solar energy to reduce the temperature within the building. Hence,  these are roof options used in buildings to reduce the heat island effect. 

Cool Roofs
Image Courtesy: GAF

Cool roofs have been widely used in commercial, industrial and residential building for more than 20 years.

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Components of Cool Roof System

Cool roofs are made of highly reflective and emission materials which would remain cooler during higher temperatures than conventional roof materials. 

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Cool roofs are selected for a project by checking their solar reflectance and thermal resistance properties.

There are multiple options for creating a cool roof. Some of the more common types include modified bitumen roofs with reflective granules, reflective coatings, and thermoplastic membranes. The manufacturing and installation processes are different, as are the life expectancies and maintenance requirements.

Also Read: What is Passive House Design?

Features of Cool Roof System

The main features of a cool roof system are:

1. Cool roofs possess higher solar reflectance. Solar reflectance is the property of the roof system to reflect the sunlight and heat away from the building, thus reducing the roof temperature. Solar reflectance is also called albedo. ( The United States Environmental Protection Agency (EPA))
2. Cool roofs compared to conventional roof system remain 28 to 33 degrees cooler during peak summer weather.
3. Cool roofs can be used on low-slope roofs or steep-sloped roofs.
4. EPA an the Department of Energy (DOE) have initiated a ENERGY STAR program to help the consumers and other purchasers to identify energy efficient roofing products. (Table-1 & Table-2). For more details visit: Roof Products Key Product Criteria | Products | ENERGY STAR

Benefits of Cool Roof System

1. Reduce Energy Consumption: Cool roofs transfer less heat to the buildings. This will help the rooms remain cooler and reduce the use of air-conditioners.
2. Reduce Air Pollution & Greenhouse Gas Emissions: As energy consumption is reduced, the production of greenhouse gases and polluted air is reduced.
3. Human Health and Comfort is Reduced: Reducing the air temperatures within the buildings without the use of air conditioning helps to prevent heat-related illnesses and deaths.

Cost of Cool Roofs

1. Cool roof coatings for low slope = $0.75 -$1.50 per square foot
2. Singly ply cool roof membrane = $1.50 -$3.00 per square foot
3. Cool roofs cost 5 to 10 % more than conventional roofs in the United States

As per a study conducted in California, cool roofs provided average yearly net savings of around 50 cents per square foot. 

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