Selecting an Energy Efficient Roof
Per a recent homeowner’s survey conducted by IKO and CertainTeed and shared on roofingcontractor.com, the primary reason for these homeowners to go with a specific roofing contractor wasn’t necessarily price, it was information. Customer’s want to be empowered to make informed decisions on the technical aspects of their roof selection. Your roof is the single most important aspect, and first line of defense for the structural envelope.
In Florida, the number one energy concern is keeping the sub-tropical heat out. When building a new home or building, or if having a new roof put on, choosing the right material for your roofing project is essential. As an example, asphalt shingles are the most common residential roofing materials used and are also the least efficient. The asphalt material absorbs heat. Asphalt shingles can approach temperatures of 180 degrees Fahrenheit on hot sunny days. This heat radiates through the roof and into your home or business. If you are considering a new roof, Wave Energy wants to talk to you about efficiency first.
What makes a roof energy efficient?
The Material. For a roof to be more efficient, it needs to block or reflect more of the heat than it absorbs. When a roof absorbs heat, that heat is transferred into the living space through radiance (heating the air), and via conduction (through support beams, the ceiling, and other materials that act as thermal bridges). A roof that reflects more of the sunlight and absorbs less energy is going to keep the interior cooler.
Roofs that have a higher Solar Reflectance Index (SRI) such as a white or light colored TPO, PVC and Elastomeric Coatings for commercial applications or products such as Landmark Solaris® shingles for residential offer the best efficiency ratings. Metal roofs also provide strength, durability, and high emittance. One step beyond is to apply a cool roof construction with metal roof which effectively creates a small air gap between the top metal surface and the roof deck. The metal reflects sunlight, and has a high emittance which is not transferred to the deck, but rather to the air gap and atmosphere. Concrete tile roofs also provide higher than normal efficiency ratings.
Below is a quick table showing various roofing materials and their SRI ratings. Data provided by the Lawrence Berkeley National Laboratory. For more information on cool roof studies, read the following LBNL Publication (PDF)
SRI of Roof Materials Table