How do I stop cold air from leaking through windows?

Start with the obvious leaks. If you can feel air moving around a window, seal gaps with caulk or weatherstripping before you blame the glass itself. Draft stoppers, insulating curtains, and clear window film can help too, especially in older homes and rentals.

The Department of Energy treats air sealing as the first move because it is usually the cheapest one with the biggest payoff. Cracks around windows, doors, vents, and trim can waste more heat than people expect. Fixing those gaps often makes a room feel warmer without touching the thermostat.

If a window still feels cold after you seal the easy spots, the problem may be the frame, the sash, or the whole wall assembly. At that point, storm windows or a more serious weatherization fix may be worth the money.