New roofs are made with technology and materials that reflect more sunlight away from your home to help keep you cool during the hot summer months. A new roof will have a higher “reflectance value” than older models, meaning they don't absorb as much solar heat. A cold roof is designed to reflect more sunlight than a conventional roof, absorbing less solar energy. This lowers the temperature of the building, just as wearing light-colored clothing keeps you cool on a sunny day.
Conventional roofs can reach temperatures of 150°F or higher on a sunny summer afternoon, with sunshine. Under the same conditions, a reflective ceiling may stay more than 28°C (50°F) cooler. This can save energy and money in buildings with air conditioning, or improve comfort and safety in buildings without air conditioning, by reducing heat flow from the roof to the occupied space. Most cold roofs have high “thermal emissivity”, the ability to emit heat by emitting “thermal infrared radiation”.
Almost any type of building can benefit from a cold roof, but consider climate and other factors before you decide to install one. Talk to your roofer to ensure that all products planned for your new roof have the highest Energy Star rating. In fact, according to Energy Star, Energy Star shingles can reduce the surface temperature of a roof by up to 50 degrees, reducing the amount of heat transferred to a house or building. This decrease in roof temperature translates into a 10 to 15 percent reduction in the amount of air conditioning or heating needed to maintain a home.
However, if you want a nice and cool home during the hot summers, you can opt for one of the many cool roof options, such as metal roofing. If the roof is not well ventilated, hot air can be trapped inside the attic and cause the entire house to gradually heat up, like an oven. In warm, humid places, where roofs are exposed to algae or mold growth, dark growths may be more visible on light-colored roofs than in dark ones. In cold climates, roofs can accumulate moisture through condensation, and cold roofs may be more susceptible to accumulating moisture than dark roofs of the same design.
Requirements for cold roofs, such as minimum solar reflectance and thermal emittance values, vary depending on the standard or program, location, building type, and roof slope. A new roof is built with the latest advances in building technology, such as roofing materials with high shingle ratings and Energy Star ratings. For example, stone-clad steel roofs are lightweight and can be installed over existing roof structures, which can save money. Before hiring a roofing contractor, you can call ahead to make sure they have the energy-saving shingles and roofing materials you're looking for.
In fact, a federal study has shown that plywood under dark roofs under direct sunlight is consistently 10 to 15°F warmer than plywood boards under light-colored ceilings. There are many types of roof systems available, but the solar reflectance of the surface of the roofing product, the outermost layer of the roof exposed to the sun, also known as the roof cover, determines if the roof is cold or not. If you are building a new home, you can decide during the planning phase what type of roof to install and if it should be a cold roof. The easiest and least expensive way to cool your roof is to choose a cold cover during a new construction or when the existing roof cover needs to be replaced.
A cold roof doesn't necessarily cost more than a non-cold one, especially if you're installing a new roof or replacing an existing one. Their rugged construction also helps them withstand strong winds, improves their fire resistance (useful if lightning strikes the house) and makes them less susceptible to hail damage, reducing roof maintenance and repair costs. Green roofs are “inverted roofs”, meaning that the waterproofing membrane is located beneath plants and most roof components. .
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