I put my hand near the bottom of my front door one cold January evening. Cold air was streaming in like the door was open a crack. It was not. The gap under the door was maybe half an inch. Invisible unless you looked. But it was letting heated air out and cold air in twenty-four hours a day.

A twelve-dollar draft stopper closed that gap. My heating bill dropped by about fifteen percent the following month. The house felt warmer. The thermostat did not cycle on as often. Twelve dollars paid for itself in two weeks.

Where Drafts Actually Come From

Exterior doors are the biggest offenders. Over time, the weather stripping along the sides and bottom compresses and loses its seal. The door itself can warp slightly with humidity changes. Even a gap you cannot see with your eyes is big enough for air to flow through.

Windows are the second source. Single-pane windows especially lose heat through the glass itself, but even double-pane windows can have drafty frames if the caulk around them has dried and cracked.

Types of Door Draft Stoppers

Twin draft stoppers — the kind that slide under the door with a foam tube on each side — work the best. They stay in place when the door opens and closes. You do not have to reposition them. I installed one on my front door in about three minutes. No tools. It slides on and stays.

Fabric tube stoppers — the kind you lay against the door — are fine for interior doors or rooms you do not use often. They slide around on hard floors and you have to put them back every time you open the door. Annoying for a front door you use multiple times a day.

Adhesive weather stripping works for the sides and top of the door frame. It comes in foam or rubber rolls. Peel and stick. If the existing weather stripping is flattened or cracking, replace it. The materials cost under ten dollars.

How to Find All Your Drafts

Wait for a cold day. Light a candle or incense stick. Hold it near every door frame and window edge. If the flame flickers or the smoke blows sideways, you have a draft. Mark the spot with painter’s tape. Fix them all in one afternoon.

I found four drafts I did not know about — the front door, the back door, one living room window, and the gap under the garage door leading into the house. Four draft stoppers and a roll of weather stripping cost me under forty dollars total. The heating bill dropped noticeably the next month.