Toss a Roadblock in Cold-Seeking Path With Attic Insulation

Wondering how you can shave 20% a month from your summer energy bills and collect those rebates promised by Gov. Gray Davis?

If you use air-conditioning, a big part of the answer could be right over your head--your attic’s insulation.

A typical one-story, 1,800-square-foot home with central air-conditioning and gas heat could cut about a third of its air-conditioning costs over the summer--that’s about 10% of all electrical use--by increasing attic insulation from R11 to R19, said Evan Mills of Lawrence Berkeley National Laboratory, a U.S. Department of Energy lab.

Insulation works by throwing roadblocks in the cold-seeking path normally taken by warm air. In the winter, heated air leaves living spaces and flows to unheated attics, garages and the outdoors. In summer, heat from outside heads for air-conditioned spaces, moving by conduction through walls, floors and ceilings. The R-value in insulation measures thermal resistance, the ability to slow heat transfer. So the higher the R-value, the better.

Mills use the lab’s Home Energy Saver (https://HomeEnergySaver.lbl.gov) and found the typical house also could save 13% on winter heating bills with the R19 upgrade. Although heavier insulation would save even more in the winter, it would tend to make the house too hot in the summer if ventilation is inadequate, he said. If the house needs a new roof, selecting a light color material would save an additional 11% on summer energy bills, Mills said.

To get a customized energy saving plan, check gas and electric bills for rate information, measure existing attic insulation depth, count the number of doors and windows you have, and log on. For more information on insulation, try: U.S. Department of Energy, https://www

.eren.doe.gov/consumerinfo; and Energy Guide, www.energyguide.com/info/insulation2.asp.