Are Cool Roofs really beneficial?
For years we have heard of all the great benefits of a light colored roof. There is a measurement for the reflectivity of a roof surface called the SRI or Solar Reflective Index. The experts at LEED (Leadership in Energy and Environmental Design) require an SRI of 78 or greater. Most white surface roofs have an SRI around 100. The surface temperature of a white roof can be up to 80 degrees cooler than a black roof. That cooler surface temperature ultimately affects the interior temperature of the building when a roof is poorly insulated. For those of us in the northern half of the country, this cooling benefit comes into play for about 3 months out of the year during the summer months. In the winter months the darker color roofs absorb more heat which can also transfer into the building in the colder months and help snow to melt off your roof.
The key to maintaining ambient temperatures in a building through all months of the year is to add more roof insulation. By adding a few more inches of insulation you can retain the hot and cold air in your building and minimize the affect s of the outside temperatures on your interior. LEED recommends an R-value of 30 for your roof insulation. This is approximately 5 inches thick. Most building codes these days suggest an R-20 which is 3.3 inches thick. Adding insulation to your roof will more than pay for itself in energy savings over the life of the roofing system no matter the color of the roof surface. Of course other factors like energy efficient windows and non-incandescent light bulbs will also come into the equation too. Spending a little extra money on the upfront costs of your roof will pay off over time.