Common locations for air leaks in basements are along the top of the basement wall where the cement or block foundation comes in contact with the wood frame. These leaks can be easily sealed in the parts of the basement that are unfinished. Also, look out for and seal around all plumbing, furnace flues, and duct runs that go through the basement ceiling to the floors above. Visit Seal and Insulate with ENERGY STAR for more information.