7 Steps to an Energy-Efficient House: 1. The Basement
Insulate and air seal the basement or crawl space to bring it inside the thermal envelope
Editor's introduction: With energy prices rising again, many homeowners are planning energy-efficiency improvements to their homes. But most people are unsure of where to begin, and even seasoned builders don’t always know which priorities should rise to the top of the list. Betsy Pettit, an architect at Building Science Corporation, recommends starting where you can get the most bang for the buck.
If you can only afford one step, replacing an aging heating appliance may be the best investment. According to Pettit, "An old furnace or boiler is often the worst energy user in an old house. Many houses built prior to 1920 still have old coal-fired boilers that were converted to gas or oil. These units are workhorses, but use a lot of energy. A new furnace or boiler can save energy dollars right away. Replacing window air conditioners with a central system also can save energy right away, as long as the ductwork has been placed in the conditioned spaceInsulated, air-sealed part of a building that is actively heated and/or cooled for occupant comfort. ."
If you're planning a major retrofit involving multiple steps, however, it's probably best to start in the basement.
Step One: Bring the basement or crawl space inside the home's thermal envelope
Warm, dry basements and crawlspaces can extend living and storage space. In an old house, a wet basement is frequently the source of high levels of indoor humidity. They can also harbor mold growth that gets distributed around the house.
Closed-cell spray polyurethane foam — installed around the rim joist areas and on the basement walls — is a fast, effective way to bring these areas into the conditioned space while sealing cracks between the foundation and floor framing that let air into the house. Most building inspectors require foam installed on basement walls to be protected with a layer of gypsum drywall as an ignition barrier.
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