When re-roofing, choose
Energy Star-labeled roofing materials with high solar reflectance—the percentage of the sun's energy reflected by the roof surface (commonly called a "cool roof," less commonly called "tiles of extreme hipness"). Like wearing white on a sunny day, roofs with higher reflectance absorb less solar energy, keeping your home cooler and more comfortable in hot weather. Energy Star roofing can reduce the need for air conditioning by 10 to 15 percent at peak times, and depending on your climate,
a cool roof can potentially cut your energy bill by up to half.
Roof repair might not be necessary as often with cool roofs. They can last longer before needing replacement, because high temperatures, among other factors, shorten the lifespan of roofing materials. Cool roofs also help lower the air temperature surrounding houses, which helps fight the "heat island effect"—increased air temperature (2 to 8 degrees Fahrenheit) in cities versus rural areas. Using less air conditioning and fighting the heat island effect directly decrease environmental pollution. So what are you waiting for?
Energy Star roofing materials can reduce the temperature of a roof by up to 100 degrees. The Energy Star criteria differ for low-slope roof (less than 2 inches of rise over a 12-inch span, or 2:12 inches) and high-slope roofs (2:12 inches or greater). To qualify for the Energy Star label, a low-slope roofing material must offer an initial solar reflectance of at least 0.65 (on a scale of 0 to 1); high-slope roofing material must have an initial solar reflectance of at least 0.25.
Time to cover your roof with tin foil? Not exactly. Instead, use single-ply membranes or paint-on coatings on low-slope or high-slope roofs. Other common low-slope cool-roof materials are modified bitumen (asphalt), polyurethane foam, and standing-seam metal. Other common high-slope cool-roof materials are cement or ceramic tile, and metal shingles. (Save the foil for your DIY hot dog oven.)
1. Measure to determine the slope of your roof. Remember, more than 2 inches of rise over a 12-inch span is a high-slope roof.
3. Choose the highest-reflectance material available, factoring in slope and regulations.
4. Remove the existing roofing if necessary.
5. Make sure that the surface is clean and dry.
6. Install base material, if necessary.
7.
For single-ply membrane: Cut membrane to required lengths, place over the surface, and heat-seal.
For coating: Spray, roll, or brush on coating.
For modified bitumen: Apply by heat or adhesive.
For polyurethane foam: Spray on foam and apply top coat.
For concrete or clay tiles: Lay out and fasten according to manufacturer's guidelines and local regulations.
For metal materials: Contact a professional roofing contractor. (You can
search for a contractor in your area.)
Use the recommended insulation with the roof. The amount and the insulating value (
R-value) you need depend on where you live.
Install properly for maximum benefit. Lifespan of the surface and effectiveness of reflectivity depend on proper installation. If you're unsure about installation, leave it to a professional roofing contractor.
Feeling brave? Try solar panels. If you're interested in installing rooftop photovoltaic panels while you're up there, the National Renewable Energy Laboratory lists
resources for homeowners. Financial incentives may even be available.