According to the United States Department of Energy, about 14 percent of total air filtration in a home enters through a fireplace chimney. Cold drafts can enter a chimney even if the flue is pulled shut, which can make your home less energy-efficient in the winter months. There are products in the marketplace called chimney balloons that you place inside the chimney that act as draft dodgers. They stop the cold drafts, but can be expensive. One DIY solution: Rip open a cardboard box and tape it inside the chimney as a draft stopper. It will do the trick and help you save up to 30 percent on your heating bill. Just remember to remove the box before starting a fire!