Twenty-five percent of your home's heat can escape through cracks, crevices and leaks in and around windows and doors. One of the biggest culprits? In-window air conditioning units. Now is a good time to remove these units and put them into storage. If that isn't feasible, do the next best thing: Wrap them up. Cover the unit in insulation, wrap it in plastic sheeting and use all-weather tape to secure it in place. You can also buy air conditioner covers that are designed to fit snugly around the unit from your home improvement store.