"This article first appeared in the Austin American Statesman. Don't Let Your Roof Take the Heat "Tips to keep your attic cool"By Marc Richmond-Powers, City of Austin Green Building Program
Picture this: It's a hot and humid Austin summer day. You head for the indoors and some relief from your trusty air conditioning (A/C) system. Three hours later, you're slightly cooler, but you're wondering why your A/C unit hasn't shut off yet.
Here's why: all day long, solar radiation has been heating up your home through the windows, walls, doors and especially the roof. Your attic temperature can easily reach over 140 degrees. That heat up there is working its way through your meager attic insulation into your home and through the A/C ductwork, located in your attic, into your cooling system. Your A/C system has to fight that added heat to change all that hot air in your home into cool air.You can install solar screens for the windows, porches around the house for shade, and plant trees around the home, but what do you do about the roof which accounts for a third of all the heat build-up of your house?
Here are a few options: Ventilate your attic with ridge and soffit vents. Vents are louvers, grills, or screen materials which allow passage or air through them. They are typically installed along the top peak (ridge) of your roof, at the top of the side wall (gable), and on the underside of your roof overhang (soffit). Ventilation moves air through your attic by force of wind or by heat rising through natural convection. This leaves cooler air sitting on top of the insulation on the attic floor. Ventilation also has the ability to remove humidity which has built up in your attic and which reduces the effectiveness of your insulation. It is often best to hire a contractor to install these.
Insulate your attic floor to R-30. R-30 is roughly a10 inch thick layer of insulation material above your ceiling. This is a job for any handy homeowner or it could be handed over to a contractor. When installing the insulation, be careful not to block your vents.
Install a radiant barrier between your roof and your attic insulation. A radiant barrier is an aluminum foil material which prevents 95 percent of the heat that radiates from your roof from reaching the insulation on your attic floor. It comes in a roll and is stapled to the underside of your roof rafters. Radiant barriers are sold in most building material supply centers and can be easily installed by a homeowner. This system can save you up to eight percent on your summer cooling bills.
copyleft 1997: You are encouraged to copy and redistribute this article provided that you acknowledge the City of Austin's Green Builder Program as the source. Please attach this statement. "
What are some other things you can do to ensure that your air is working at it's best? 1. Turn your air on early - BEFORE the heat of the day, IF you are going to be home. If you are not going to be home a thermostat that you can set is an especially good way to keep your home cool. Setting this thermostat to turn on at a very low rate while the home is unoccupied keeps the hot air from settling in the house, but still does not use too much energy. 2. Make sure to keep drapes drawn. If your home has skylights or larger windows, you might want to consider placing an outside screen or other heat reflecting material over these. 3. Set the thermostat to a comfortable setting (78 degrees if possible - this is the energy star recommended setting and will save you). If you set the degrees for as low as it will go in hopes that your house will cool faster, your unit is just going to burn out faster.
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