Air leaking through holes and cracks account for up to 20 percent of heating and cooling costs (or up to 10 percent of total energy costs) in a typical home. Many air leaks are easy to find because they are easy to feel and are located in common areas of the house—especially around windows and doors. But hidden air leaks in attics, basements, and around chimneys are often more significant sources of energy loss. Seal these areas properly to keep your energy from slipping away.