Is energy efficiency a concern for you? You’re not alone. Every year, Americans spend around $40 billion on air conditioning alone. That’s the equivalent of a sixth of all the electricity the United States consumes annually!
There are many ways to address energy efficiency at home, and it starts with identifying what contributes the most to your power consumption. For decades, space conditioning (heating and cooling) has been the typical US household’s largest energy expense. While appliances, electronics and lighting are slowly catching up, heating and cooling still make up a sizeable portion of the pie: about 48%, according to Energy Information Administration surveys.
The Case for Energy-Efficient Roofs
Climate is a big factor when you’re choosing a roof, but for most people, this is limited to how well the roof can protect their homes against the elements. But roofs also play a big part in making homes more energy-efficient.
Because the roof is responsible for about 20% of a home’s heat loss in winter and 5% of its heat gain in summer, any improvement in its energy performance will have a tremendous impact on the entire home’s energy efficiency. A roof system designed with energy efficiency in mind will be able to reduce the amount of power your HVAC system needs to stabilize indoor temperatures, which will in turn be a huge load off of your energy bill.
Building an Energy-Efficient Roof
Roof energy efficiency isn’t as easy to measure as, say, window energy efficiency. This is because so many factors contribute to a roof system’s overall energy performance, the biggest of which include:
Among these factors, roof and attic insulation provide the simplest pathway to setting energy performance benchmarks. In the case of insulation, energy efficiency is rated in R-value, the measure of how well a material is able to prevent heat transfer. As a general rule, the higher the R-value, the better a roof is at preventing heat loss. (Heat gain prevention is more dependent on sun control than on insulation.)
Different climate zones have different space conditioning requirements, so ideal R-values vary widely. For instance, recommended ratings for cathedral ceilings in Zone 3 (mixed-humid, hot-humid and hot-dry) are R22 to R38, while Zone 6 (cold) calls for R49 to R60.
These R-values are recommendations by the Department of Energy and the International Energy Conservation Code (IECC), the model building code for the United States.
Did You Know?
You can compute how much energy you can save through your roof using Oak Ridge National Laboratory’s Roof Savings Calculator at http://rsc.ornl.gov/.
The online tool (which is also available as a web service) also lets users compare the performance of different roofing options, which will come in handy if you’re planning a reroof.
Is there such a thing as an ideal energy-efficient roof? Stay tuned for the second part of this blog series to find out!