Air leaks can cost you by letting heat and cool air escape. Many homes, especially older ones, have gaps in their outer shell that allow air to escape. Common air leaks happen around fireplace chimney cases, light fixtures, windows and doors, basement sills, interior cavity walls, attic hatches, plumbing, trim areas, floors and outlets and wall switches. Sealing these leaks can make your home cozier and more efficient while helping you better manage your electricity bill.