Weatherstripping and Draft Proofing: The Cheap Fixes That Work

Weatherstripping is the cheapest energy work there is, and the most satisfying, because you fix the draft you can actually feel.

Two things to be clear about up front. First, it works — a properly sealed door is dramatically better than a bad one. Second, doors and windows aren't where most of your air leakage is. The attic floor and rim joist move far more air, and they should get your attention first. See how to air seal a house.

Do both. Just don't expect weatherstripping alone to transform a bill.

Which weatherstripping should you use?

The commonest mistake is buying one product for every gap. Different joints move differently.

Two rules that cover most decisions:

• Compression joints (door against its stop, sash against frame) want a gasket that squashes — V-strip, bulb seal, foam.
• Sliding joints (under a door, sliding sash sides) want a sweep or brush, because a gasket would be shredded by the motion.

How do you weatherstrip a door?

An exterior door has four leakage paths, and people usually fix only one.

1. The two sides and the top — where the door meets the stop. V-strip on the jamb or a bulb seal on the stop.
2. The bottom — a sweep on the door, or a threshold with a replaceable insert, or both.
3. Around the frame itself — the gap between the door frame and the rough opening in the wall, usually hidden behind the interior trim and often loosely stuffed with fibreglass. This can leak more than the door does. Remove the trim, seal the gap with low-expansion foam or backer rod and sealant, and reinstall.
4. The hardware — worn strike plates and misaligned latches leave the door sitting proud of the stop, so no gasket can seal it.

Test it: close the door on a strip of paper and pull. It should drag noticeably. Do this at several points around the perimeter — if it pulls out freely at the top corner, that's your leak. Adjust the strike plate or hinges before adding more gasket; the fix is usually alignment, not material.

Same treatment for the garage-to-house door and any attic hatch or pull-down stair, which is one of the largest ceiling leaks in many houses and takes weatherstripping plus an insulated cover.

How do you seal a drafty window?

Operable windows (double-hung, casement, slider):

• V-strip in the sash channels on double-hungs
• Foam or bulb gasket where the sash meets the sill and header
• Seal the meeting rail on double-hungs — the joint between upper and lower sash is a classic leak
• Check and adjust the locking hardware. A sash lock isn't only security; on a double-hung it pulls the meeting rail tight. A window that doesn't lock properly can't seal.

Fixed windows and frames:

• Caulk the exterior perimeter where the frame meets the siding or trim
• Caulk the interior trim-to-wall joint
• Seal the rough opening gap behind the trim, as with doors — this is often the real leak

Windows you won't open all winter: rope caulk pressed into the sash joints, or an interior shrink-film kit. Both are removable in spring and cost very little.

If your windows are single-pane, weatherstripping plus a storm window closes much of the gap to a modern unit for a small fraction of replacement cost — see are new windows worth it.

Where are the biggest air leaks in a house?

Small individually, meaningful together, and nearly all cheap to fix:

• Electrical boxes on exterior walls. Foam gaskets behind the cover plates. There are usually a lot of them. Turn off the circuit first.
• Where pipes, wires and cables enter the house — hose bibs, dryer vents, AC line sets, cable and utility entries. Caulk or foam.
• The dryer vent flap. If it doesn't close fully, it's an open hole to outside.
• Mail slots and pet doors. Both leak; both have insulated or gasketed replacements.
• Window air conditioners left in over winter. A large permanent hole. Remove them, or cover inside and out.
• Unused fireplaces. An open damper is a chimney-sized leak. Keep it closed when not in use and consider an inflatable chimney balloon or a top-sealing damper. Never block a flue serving an active appliance. See what to do with an unused chimney.
• Recessed lights in the top-floor ceiling. Often significant leaks — see how to air seal a house.
• Whole-house fan louvres, which leak all winter unless covered — see Attic fan vs whole house fan.

How do you find drafts in a house?

• The damp hand test. Moving air feels cooler on wet skin. Run the back of a damp hand slowly around a perimeter on a cold or windy day.
• A smoke pencil or incense stick. Shows the direction and strength of flow.
• A thermal camera, even a phone attachment, in cold weather.
• A blower-door test. The professional version — the house is depressurized so every leak becomes obvious, and you get a measured number before and after.

Windy days make everything easier to find.

What will draft proofing not fix?

Be realistic about the limits:

• It won't fix a cold room caused by inadequate insulation or an undersized duct run. Sealing addresses air; insulation addresses conduction. See how to cool an upstairs room for the analogous cooling problem.
• It won't fix cold glass. Discomfort standing next to a single-pane window is radiant, not a draft.
• It won't fix duct leakage, which in many houses wastes more than every window and door combined — see ductwork problems and cost.
• It won't compensate for a stack effect driven by big attic leaks. Sealing the front door while the ceiling plane is wide open just changes where the replacement air comes from.

Don't forget ventilation

As a house gets tighter, deliberate ventilation matters more. This isn't an argument against sealing — random leaks ventilate badly and unpredictably — but after significant work:

• Make sure bath and kitchen exhaust vents outside and gets used
• Watch indoor humidity — see home humidity control
• If you have naturally drafting gas or oil appliances, have combustion draft checked after major sealing
• Consider balanced ventilation on a well-sealed house — see HRV vs ERV explained

The bottom line

Match the gasket to the gap: compression seals where surfaces press together, sweeps where things slide. On doors, fix the alignment before adding material, and don't forget the gap behind the trim — it often leaks more than the door. Do the small overlooked leaks too: outlet gaskets, penetrations, the dryer flap, the fireplace damper. It's an afternoon and a small budget, and it fixes the drafts you actually feel — just do the attic floor and rim joist as well, because that's where the bigger losses are.

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