Here are two easy and affordable ways to seal your windows: 1) Add 3/8” weather stripping under the window to close gaps at the sill. Stick the adhesive side in place, trim around sensors if needed, and peel off the backing. It might make the window harder to close, but it creates a snug seal against the cold. 2) Check for cracks near the sill. Remove the old caulk with a utility knife or a flat head, then apply silicone. Smooth it out with a wet finger or wipe for a clean finish. For extra insu