| $ | During winter, shut the windows tight and use window film to improve insulation and protect against drafts. Keep the shades/blinds open during the day to let sunlight in; close them at night. During summer, keep windows and shades closed during the hottest parts of the day to keep the sun out and open at night to let the cool breezes in. |
| $$ | Caulk the windows to prevent air leaks (DIY) |
| $$$ | Replace with more energy-efficient windows (info) |