Heat loss through windows is responsible for 25-30 percent of heating energy use, according to the U.S. Department of Energy. But it doesn't have to be that way, because weatherstripping is simple and probably the most cost-effective way to keep heating costs down.
Pro tip: To check if you have a draft issue, close a door or window on a strip of paper. If the paper slides easily, you need to update your weatherstripping.
https://www.housebeautiful.com/lifestyle/cleaning-tips/a22652916/fall-home-maintenance-checklist/
