The material on your roof itself can contribute to how energy efficient your home is. There are a number of different options when choosing a roofing material. Each type of material is designed for a particular use and comes with its distinct set of advantages and disadvantages. Roofing materials can include asphalt, metal, wood, clay, cement and fiberglass.
More than 70% of North American homes are roofed with tar composite shingles. These shingles are made of cellulose fibers or fiberglass and coated with asphalt and topped with a mineral aggregate coating for protection.
Wood shingles, also called shakes, are typically made from western red cedar and are resistant to knots and rotting. The lifespan of this type of roofing is approximately 20-25 years.
Metal roofing is constructed of either aluminum or corrugated steel panels. Metal roofs are expensive to install, but can last the life of a house. Other downsides to a metal roof are that they are noisy in rain and hail storms and they conduct heat far faster than wood, meaning they must be well insulated. On the plus side, metal roofs also reflect light, making them relatively energy efficient.
Clay tiles are also becoming more popular, especially in states such as California where the climate is relatively stable year-round. Alternatives to clay tiles are cement, slate and plastic tiles. Each is available in a variety of colors and styles to suit any decorator’s vision. Tiles can have an additional energy efficient coating applied at the factory or during the installation to help save on energy costs.
Regardless of what type of roofing you choose, there are 3 things to consider – emmissivity, reflectivity and insulation.
Emmissivity refers to how quickly the roof releases the heat it has absorbed.
Reflectivity refers to how much sunlight the roof reflects – the higher the number, the better.
Insulation refers to the level of insulation in the attic or roof, expressed as an R-Value.
The ENERGY STAR efficiency rating provides no specification for insulation, as it depends largely on the climate you live in. However, ENERGY STAR qualified roofs can lower the surface temperature by up to 100ºF and cut cooling demand by 10-15%.