Seal basement sill
This post is a detailed part of Home Energy 101 and is something that the average DIY can do at minimal cost to save energy and drastically cut heating bills. Did I mention warmer floors, less drafts equals warmer house? This usually makes the ladies of the house much happier
Caulking the sill plate and the rim joist stops air leaks along the foundation.
Sill plates and rim joists are usually poorly insulated (if at all) and very leaky. So if you have an unfinished basement, grab some silicone or acrylic latex caulk to seal the sill plate. If you simply have fiberglass insulation stuffed against the rim joist, pull it out. Run a bead of caulk between the edge of the sill plate and the top of the foundation wall. Use expanding spray foam anywhere there are gaps larger than 1/4 in. between the sill and the foundation. For hollow-block foundations, stuff fiberglass insulation in the holes, then seal it with expanding foam.
Caulk along the top and bottom of the rim joists and use expanding foam to seal around holes for electric, water and gas lines. Then cut rigid foam insulation to size and place it against the rim joist. Caulk around all four sides of the foam insulation.