Find and seal drafts around windows and doors
The Department of Energy's simple method for finding air leaks, then sealing each one with the right material.
Step by step
Pick a cool, very windy day. Close the windows, exterior doors and fireplace flue, turn off the furnace and water heater, and run exhaust fans that vent outside. This pulls outside air in through any leaks.
Carefully pass a lit incense stick (or a damp hand) along window frames, sashes and door edges. Smoke that wavers or gets pulled sideways marks a leak.
To test a door seal, close the door on a sheet of paper. If it slides out without tearing, the seal needs attention.
Use caulk for gaps between parts that don't move, and weatherstripping for parts that do, like doors and opening sashes.
Remove old caulk and loose paint, clean the joint and make sure it is completely dry.
Caulk gaps narrower than ¼ inch. Press backer rod into joints deeper than about ½ inch first. Fill larger gaps with expanding foam.
Hold the gun at a steady 45° angle and run one continuous bead that sticks to both sides. Smooth it with a tool, or with a damp finger only if the label allows.
Apply weatherstripping to clean, dry surfaces. It should compress when the door closes without making it hard to shut. Replace a worn door sweep.
Safety first. Check the caulk label for temperature limits. The Department of Energy recommends above 45°F, in dry weather, with no rain coming. Keep incense away from curtains, and turn the furnace and water heater back on when you're done. A tighter house needs adequate ventilation, so consider a professional energy assessment with a blower-door test.