Focus on Energy: Air-Sealing the Rim Joist

A highway of air leaks runs through just about every house. It collects traffic from every interior wall that holds a pipe or wire. If interior wall cavities are used as ducts, it’s rush hour whenever the furnace kicks on. The fast lane is the space between floor joists where air travels back and forth to the outside wall and leaks in and out around the rim joist. Blocking the access routes — every receptacle, pipe, and duct — may be the only option for existing homes, though it’s tedious and never totally effective. In new construction and major remodels, however, it’s worth blocking the major outlet. By sealing the rim joist, you avoid the need to seal all those