It can have a huge impact on your comfort and energy consumption.In the last column, we discussed having a “solar friendly” roof which faces south and is not shaded so that you can add solar water heating and photovoltaics. But did you know that your roof itself can have a huge impact on your comfort and energy consumption?
Your roof is like a giant solar collector: all day long, it sits in the sun and heats up. A lot of that heat goes into your home. Commercial building designers know this—that’s why commercial buildings have insulation. Most Maui residences could use insulation, too, or another “cool roof” measure.
What’s a “cool roof?” A cool roof not only keeps out the rain, but also blocks the sun’s heat. You end up with a more liveable and comfortable space that doesn’t need air conditioning.
Making your roof a “cool roof” is not hard. The techniques include ventilating your attic, installing insulation and/or a radiant barrier, and choosing a light-colored material for the roof itself. Did you know that by itself, a white roof will keep the roof surface 20-40 degrees cooler than a dark roof?
There are lots of ways to ventilate your attic. Among the best are a baffled ridge vent and large soffit vents. Eave vents are also common, but often are not large enough to really get the air moving. Gable vents can also work, but you need to have them on both the windward and the leeward sides of the house. You should have a total vent area of at least one square inch per square foot of attic. If you have less, that hot air will stagnate in your attic, and the heat will travel down into your living area.
Some of these techniques cost no more than their hotter alternatives. For instance, light-colored roofing is the same price as dark roofing. Other measures might cost between $.50 and $2 per square foot. However, compare this investment to the savings you’ll get by avoiding air conditioning—hundreds of dollars per year for the life of your house, in addition to the initial purchase price.
Many tips for “cool roofs” and other energy-saving measures are found in the handy pamphlet, “Hawai‘i Homeowner’s Guide to Energy, Comfort and Value.” It’s available from the state’s energy office (phone the Hilo office at (808) 933-0312) or online at www.hawaii.gov/dbedt/info/energy/efficiency/index_html.
In partnership with the state’s energy office, the Maui Weekly provides this feature to help Valley Isle homeowners reduce their utility bills and increase their environmental awareness. For more information, visit www.hawaii.gov/dbedt/info/energy.