Your windows or doors let in too much cool air in winter and warm air in summer.
Old, worn-out windows or patio doors are often leaky, which can result in high energy bills during peak heating and cooling months. The glass may be loose (in which case it should be re-glazed) or the seal between the sash and frame may have weakened. The cost of replacing failing windows is often dwarfed by overall household energy costs, but we recommend replacing old single-pane windows with modern windows that feature dual-pane Low-E glass for a substantial energy savings. If your windows are in decent shape but still leak, consider applying new weather stripping. It’s easy to install and available at most building supply stores