Insulate windows with film, curtains, or cellular shades

Windows account for 25-30% of residential heating energy loss. Adding insulation layers -- film kits, thermal curtains, or cellular shades -- significantly reduces heat transfer and can lower heating costs without renovation.

Steps

1. Apply window insulation film: Attach clear plastic film kits to the inside of window frames using double-sided tape, then shrink the film taut with a hairdryer. The trapped air gap reduces convective and radiative heat loss.
2. Hang thermal curtains: Use heavy, lined thermal curtains or drapes. Keep them closed at night and on cloudy days to trap heat inside, and open them during sunny days to allow passive solar warming.
3. Install cellular shades: Fit cellular (honeycomb) shades on windows that receive little direct sunlight. Their air pockets provide effective insulation without blocking light entirely.

Tips

• Combining film with thermal curtains provides the best insulation
• Ensure curtains extend below the window sill and fit snugly against the wall to minimize warm air circulating behind them
• Remove film kits in spring to avoid trapping excessive heat in summer