When hot air seeps out of the house when you're trying to heat it, you're wasting energy and losing money at the same time. What many people don't realize is that your fireplace can actually be to blame. A leaky chimney can suck up to 8 percent of the warm air out of your home. If you can't replace the damper inside the fireplace, do this next best thing: Cut a piece of thick cardboard to fit snugly inside. It will block drafts and cost you nothing to do. Just remember to remove the cardboard when you do plan to use the fireplace.