Draft-Proof Your Home for Free (Then Seal It for Cheap)

A draft is sneaky. You don't see it, but you feel it: a cool ribbon across your ankles, a chill by the window, a couch that never quite warms up. Then you nudge the thermostat up to compensate, and you're paying to heat air that's leaking right back outside.

The good news is that finding and blocking drafts is one of the cheapest home fixes there is. The first round is completely free, using things already in your closet. Once you know where the leaks are, sealing the worst ones costs a few dollars and an afternoon, and there's an optional upgrade box below if you want to go that far.

Why it's worth doing

Drafts make a room feel colder than the thermostat says. That's the real payoff of fixing them: you're comfortable at a lower setting, so the furnace runs less and the bill follows. In summer, the same gaps let hot air in and cool air out, so sealing them helps your air conditioner too.

It also makes the house quieter and less dusty, since the same cracks that let air in let noise and grit in with it. And it's one of the rare home projects that renters can do almost entirely on their own.

The free way, step by step

Step 1: Find the drafts

Pick a cold, windy day for the best results, since a strong breeze outside pushes more air through the gaps. Turn off anything that blows air around, like ceiling fans and the furnace blower, so you aren't chasing its breeze instead of a leak.

Then go on a hunt with one of these two tools:

• A lit incense stick. Hold it a few inches from an edge and watch the smoke. Smoke that rises straight up means still air. Smoke that flutters, gets sucked toward the gap or blows back at you means you've found a leak.
• A damp hand. Wet the back of your hand and run it slowly along an edge. Moving air feels noticeably cool on damp skin, so small drafts are easy to spot.

Step 2: Check the usual suspects

Drafts tend to hide in the same places in almost every home. Work through this list and jot down what you find:

• Window edges. Where the sash meets the frame, where two sashes meet in the middle, and where the frame meets the wall.
• Exterior doors. The bottom gap, the sides and the top of the frame. Check the door to the garage and the basement too.
• Outlets and switches on exterior walls. Air can travel through the wall cavity and out the cover plate.
• The attic hatch or pull-down stairs. A loose-fitting hatch in the ceiling can leak a surprising amount of warm air up and out.
• Anywhere pipes, cables or vents pass through a wall. Under sinks, behind the washer and around the dryer vent are common spots.
• The fireplace. An open damper is basically an open window straight up the chimney.

A simple list, with room names and spots, turns a vague feeling of "this house is drafty" into a short set of problems you can actually fix.

Step 3: Make a free door snake

The gap under a door is often the single biggest draft in a room, and it's the easiest to block. Roll an old bath towel tightly and lay it along the bottom of the door. Done.

For something sturdier that stays put, make a draft snake:

1. Cut a leg off an old pair of jeans, or use a long tube sock or a pillowcase cut into a strip.
2. Tie or sew one end closed.
3. Fill it with dry rice, dried beans, or old socks and fabric scraps. Rice and beans add weight so it stays in place; socks keep it light and washable.
4. Tie or sew the other end closed, and trim it to the width of your door.

Lay it across the bottom of any door that leaks, including interior doors to cold rooms. If you have pets or small kids who might chew on it, skip the rice and beans and stuff it with fabric instead.

Step 4: Work your curtains like a pro

Windows are a two-way street. By day, sun-facing windows let in free heat. At night, they give it right back. So:

• Open curtains and blinds on sun-facing windows during the day to let the sunshine warm your rooms.
• Close all curtains at dusk to add a layer between you and the cold glass.
• Close curtains on windows that never get direct sun for most of the day in deep winter.

Heavier curtains work best, and curtains that reach the floor or the sill do more than ones that stop short. If you have a spare blanket, you can even hang it over a particularly bad window at night. In summer, reverse the whole routine: see our guide to shading windows before noon.

Step 5: Close the fireplace damper

If you have a wood-burning fireplace, check that the damper is shut whenever there's no fire. Reach up inside with a flashlight and feel for the handle or chain. Only close it once the fire is completely out and the ashes are cold, never while anything is still smoldering. If your fireplace has a gas log set, follow its manual instead, since many require the damper to stay open or be fixed partly open. If the damper is missing, rusted or won't close snugly, have a chimney sweep take a look.

Step 6: Block off rooms you aren't using

Guest rooms, a storage room or a sunroom that's freezing all winter don't need to share your heat. Close their doors and lay a towel or draft snake at the bottom. The rest of the house holds its warmth better. Leave supply vents in those rooms open unless your HVAC installer says otherwise, since closing too many vents can strain some systems, and keep the room warm enough that any pipes in its walls won't freeze.

Mistakes that make it harder than it needs to be

• Guessing instead of testing. You'll waste time stuffing the wrong window. Ten minutes with an incense stick shows you exactly where to focus.
• Hunting on a calm day. With no wind, small leaks barely move the smoke. Wait for a breezy afternoon.
• Forgetting the attic hatch. It's out of sight, but warm air rises, so a leaky hatch in the ceiling is often a big loser.
• Opening curtains on a cloudy day. If there's no sun, there's no free heat to collect. Keep them closed on gray days in deep winter.
• Sealing everything shut. Homes need some fresh air. Keep bathroom and kitchen exhaust fans working, and never block combustion air for gas appliances.

Notes for renters and apartments

Almost everything in the free method works in a rental. Door snakes, curtain habits and closed doors leave no trace. If you go on to the upgrades, stick with removable options: foam weatherstripping tape, door sweeps that slide on rather than screw in, and window film kits, which come off in spring.

If a window or door is truly broken, cracked or doesn't close, that's a repair for your landlord, not a weekend project. Put the request in writing with your list of drafty spots, and ask whether they'd approve weatherstripping or caulk if you want to go further.

When the upgrade is worth it (and when it isn't)

Once you've found your leaks, sealing them is cheap and fast. Here's how to match the fix to the gap:

• Foam tape weatherstripping is the easiest. It sticks onto window sashes and door stops and compresses when you close them. Good for irregular gaps, and renter-friendly.
• V-strip (tension seal) is a folded strip of vinyl or metal that springs open to seal the sides of a double-hung window or a door jamb. It lasts longer than foam, but it's a little fussier to install.
• Door sweeps attach to the bottom of a door and brush against the threshold. They're the permanent version of your door snake.
• Window insulation film kits use double-sided tape on the window frame and a clear plastic sheet that you shrink tight with a hair dryer. The result is a still air pocket in front of the glass. It comes off in spring.
• Caulk is for gaps that don't move, like cracks where a window frame meets the wall or trim meets siding. Don't caulk anything that opens.

The upgrade is worth it for gaps you'd otherwise block with a towel every single night, for windows you never open in winter, and for any door where the draft is strong enough that you feel it from across the room.

It isn't worth it for a spot where a rolled towel already does the job and you don't mind the look, or for windows that are so damaged they really need repair or replacement. In that case, start with a conversation with your landlord or a contractor instead.

The bottom line

Drafts are the kind of problem you stop noticing until you fix them, and then you wonder why you waited. Light an incense stick this weekend, walk the house, and block what you find with a towel. When you want to take it further, a roll of foam tape and a film kit take care of most of the rest.

For a bigger-picture look at where your home loses energy, try our DIY home energy audit, then pair your sealed-up house with a programmable thermostat so the savings run on autopilot.