from Patrick and Bridget in Scott, WI:
#510
We have just purchased a home that has a crawl space. The ceiling of the crawl space is insulated but some of the heat ducts run below the ceiling. Should we insulate the concrete walls of the crawl space instead of the ceiling? If so, with what? Should we remove the ceiling insulation?
Yes, it would serve you best to do both.
Yes, it would serve you best to make your crawl space unvented, air sealed, properly insulated, and protected from ground moisture. These crawl spaces are known as conditioned crawl spaces. The U.S. Department of Energy’s Energy Savers Web site has a nice video which shows the features and benefits of conditioned crawl spaces. It also depicts how to do it and the materials to use.
Yes, it would be beneficial to remove the existing insulation from the ceiling of the crawl space. In addition, we recommend you air seal the ducts that are present in the crawl space. The best material for this task is duct mastic. Mastics are carefully formulated to provide permanent, air tight, flexible, and weather resistant repairs and installations on air ducts. Sealing leaking air ducts saves energy, saves money, and improves indoor comfort and indoor air quality. Apply the duct mastic at least 1/16” thick and use reinforcing mesh for all joints wider than 1/8” or joints that may experience some movement. Aluminum foil or cloth duct tapes are not good materials for duct sealing because their adhesive often fails after a short time.
Published Thursday, October 08, 2009