That is what a draught is. Not a howling gale through a broken window, but the slow, constant exchange of warm indoor air for cold outdoor air through cracks around doors, windows, floorboards, loft hatches, letterboxes and pipework. Sealing those gaps is called draught-proofing, and it is widely regarded as one of the cheapest, fastest home improvements available. Most of it can be done in a single weekend with materials that cost less than a weekly food shop, and the difference is felt the same evening: rooms warm up faster, stay warm longer, and the heating does not have to work as hard to hold its temperature.
November is the ideal month to do it. The cold has properly arrived, so draughts are easy to find with the back of your hand, but the worst of winter is still ahead, which means every fix you make now pays back for months. It also lands at exactly the moment energy costs are front of mind, with heating bills climbing and households looking for savings that do not involve sitting in a cold house.
This guide walks through the whole job room by room: how to find your draughts, what to seal with, what it costs, and just as importantly, what you must never block. Because draught-proofing done badly can cause condensation, mould, and in rare cases a genuine safety hazard. Done properly, it is one of the most satisfying weekend projects a home can offer.
Why Draughts Cost You More Than You Think
A draughty home does not just feel uncomfortable. It forces your heating system to replace warm air that is constantly escaping, which means longer boiler run times and higher bills for the same level of comfort. Energy guidance commonly cited in the UK suggests that professional draught-proofing of windows and doors for a whole house costs around £250 and saves around £55 a year, while sealing an unused chimney can save a further £45 a year. Those figures are averages for Great Britain, not promises for any particular home, but they illustrate the point: the payback period is measured in a few years, and the comfort gain is immediate.
The effect is bigger in older homes. Houses built before modern airtightness standards can have the equivalent of a small open window's worth of gaps scattered across the building, even when every window is shut. Newer homes are tighter, but they still develop gaps as frames settle, seals age and timber moves with the seasons. No home is completely draught-free, and almost every home has at least one gap worth sealing.
There is also a comfort argument that has nothing to do with money. Draughts create cold spots and uneven temperatures: the chair by the window is chilly, the hallway is cold, the bedroom above the garage never quite warms up. Sealing the gaps evens the house out, so every room feels closer to the temperature the thermostat claims. People often find they can turn the thermostat down a degree or two once the draughts are gone, and that single degree is itself worth a meaningful saving.
First, Find Your Draughts
Before buying anything, spend twenty minutes finding out where your home actually leaks. The best time is a cold, windy day, when the pressure difference between inside and outside makes draughts obvious. Walk slowly around each room with the back of your hand held near the places listed below. The back of the hand is more sensitive to moving air than the palm, and it will pick up draughts your face misses.
The candle and tissue tests
Two old-fashioned tests still work well. Hold a lit candle or a strip of lightweight tissue near a suspected gap: if the flame flickers sideways or the tissue flutters, air is moving through. Use the candle test with care, keeping the flame away from curtains, paper and other flammable materials, and never leave a lit candle unattended. The tissue test is the safer choice around soft furnishings.
The usual suspects, in order of impact
Start with the biggest leaks first. External doors are the worst offenders in most homes, particularly the gap under the door and the frame around it. Windows come next, especially older sash windows and any window whose seal has hardened or shrunk. Then check the loft hatch, which often has no seal at all and sits directly below a cold roof space. After that, look at letterboxes and keyholes, gaps in floorboards, skirting boards that have pulled away from the wall, pipework passing through external walls, and unused fireplaces and chimneys, which can act like open vents pulling warm air straight up and out of the house.
Make a simple map before you shop
Note each draught you find, room by room, with a rough size of the gap. A hairline crack and a finger-width gap need different products, and buying the right materials first time saves a second trip. Measure the length of each door and window frame you plan to seal so you know how many metres of strip to buy. This small bit of preparation is what turns draught-proofing from a vague intention into a single-afternoon job.
Doors: The Biggest Win in the House
External doors deserve your attention first, because they combine several leaks in one place: under the door, around the frame, through the letterbox and through the keyhole.
Sealing the gap under the door
A brush strip or a flexible rubber sweep fixed to the bottom of the door closes the gap to the threshold. Many versions are self-adhesive or screw on in minutes, and some can be cut to length with scissors or a small saw. Choose a strip that brushes the floor lightly when the door closes; if it drags hard, it will wear out quickly and make the door difficult to shut. For doors over uneven floors, a flexible sweep copes better than a rigid one.
Weather strips around the frame
Self-adhesive foam or rubber strips, often called V-strip or compression seals, stick to the door frame so the door compresses them when it closes. Foam is cheapest and easiest, but it compresses permanently over time and usually needs replacing every couple of years. Rubber and silicone strips last longer and seal better, and they are worth the small extra cost on doors that get daily use. Clean the frame and let it dry before sticking anything down; dust and damp are the two reasons self-adhesive strips peel off early.
Letterboxes, keyholes and door furniture
A letterbox flap that hangs open is a surprisingly large leak. A brush-lined letterbox plate or an internal draught excluder box fitted behind the letterbox closes it while still letting post through. Keyhole covers are tiny, cheap and effective, and they also stop the thin whistle some keyholes produce on windy nights. Check the door's hinges and lock too: a door that has dropped on its hinges will not seal properly no matter what strip you fit, and adjusting or re-packing a hinge is often a ten-minute fix.
Windows: Seal the Frame, Not the Vent
Windows leak in two places: between the frame and the opening sash, and between the frame and the wall. The first is yours to fix; the second may need filler or professional attention if it is large.
Casement windows
For windows that open on hinges, self-adhesive foam or rubber strips around the opening edge work exactly as they do on doors. Close the window onto the strip and check that it latches without force. If the window will not close, the strip is too thick; if it closes with no resistance at all, the strip is too thin or has been fitted on the wrong side of the rebate. Fitting the strip to the frame rather than the sash usually gives a cleaner result.
Sash windows
Sliding sash windows are trickier because the sashes move past each other. Brush-pile strips, which are thin strips of fine bristles set in a carrier, are made for this job and fit into the grooves the sashes already slide in. They stop draughts without stopping the window from moving. Fitting them takes patience rather than skill: work one sash at a time, measure twice, and test the slide before moving on. If a sash window is painted shut or swollen with damp, deal with that first, because no seal will fix a window that cannot close squarely.
Secondary glazing and window film
If your windows are single-glazed and replacement is not on the cards, two low-cost options add a useful extra layer. Secondary glazing panels, fitted inside the existing window, create a trapped air gap that cuts both draughts and heat loss. Transparent window film, shrunk taut with a hair dryer, does a similar job for a single season at a fraction of the price, and it is a popular choice for rented homes where permanent changes are limited. Neither replaces proper double glazing, but both make a cold room noticeably more comfortable.
What never to block on a window
Modern windows have trickle vents, the small slots at the top of the frame that provide background ventilation. Do not seal them. They are there deliberately, to let a small, controlled amount of fresh air in and to reduce condensation. Blocking them trades a draught for damp, which is a worse problem. The same rule applies to any vent built into a window frame: seal the gaps the window was not designed to have, and leave the ventilation the window was designed to provide.
Floors, Skirting Boards and Pipework
Once doors and windows are done, the next tier of draughts is less obvious but still worth sealing, especially in older homes with suspended timber floors.
Gaps between floorboards
Floorboards shrink as they dry out, and the gaps between them can leak cold air from the void beneath the floor. Flexible filler designed for floorboards, or thin strips of wood glued into wider gaps, both work well. Avoid rigid filler in wide gaps, because boards move with temperature and humidity and rigid filler cracks out. If you have carpet, the draught is usually already reduced, but the gap under the skirting board may still leak.
Skirting boards and wall junctions
Skirting boards pull away from walls over time, leaving a thin slot that runs the length of a room. A bead of flexible sealant along the top edge of the skirting board closes it neatly. The same treatment works where pipework passes through an external wall: seal around the pipe with flexible sealant or expanding foam for larger holes, taking care not to block any ventilation the pipe serves.
Loft hatches and ceiling penetrations
The loft hatch is one of the most commonly missed draughts in a house, because nobody looks at it. Fit a compression strip around the hatch frame and, if the hatch is a plain board, glue a piece of insulation to its upper face. Check too for holes in ceilings where cables, pipes or light fittings pass into the loft; these leak warm air directly into the cold roof space. Seal them with flexible sealant, keeping clear of recessed light fittings, which need air space around them for heat dissipation.
Chimneys and Unused Fireplaces
An open, unused chimney is effectively a hole in your roof that pulls warm air out of the room all day and all night. It is also one of the easiest big wins in draught-proofing, provided it is done safely.
Chimney balloons and fireplace draught excluders
A chimney balloon is an inflatable plug fitted just above the fireplace opening; inflated, it blocks the flue, and it can be deflated and removed in seconds if you ever want a fire again. Purpose-made fireplace draught excluders, which are padded covers that sit in the opening, do the same job. Either option can save a meaningful amount of heat, with published estimates putting the annual saving from sealing an unused chimney at around £45 for a typical home.
The safety rules that are not optional
Never block a chimney that is in use, and never block a flue serving a gas appliance, an open fire or a solid-fuel stove. Those appliances need their flue to carry combustion gases safely out of the house. If you are unsure whether a chimney is truly disused, have it checked before sealing it. And make the blockage visible: a balloon or excluder that someone could forget is a hazard if a fire is later lit beneath it. Attach a clear tag or note to the fireplace stating that the chimney is sealed, and remove the blockage before any fire is lit.
What You Must Never Block
This is the most important section of the whole guide, because draught-proofing has one genuine danger: sealing the ventilation a home needs to stay healthy and safe.
Deliberate ventilation stays open
Trickle vents, airbricks, wall vents, underfloor grilles and extractor fans exist to provide fresh air and to control moisture. Airbricks ventilate the void under suspended floors and prevent damp and timber decay. Wall vents supply combustion air to gas appliances. Blocking any of these can cause condensation, mould growth, and in the case of gas appliances, a dangerous build-up of combustion gases. The rule is simple: seal unwanted gaps, never deliberate openings.
Rooms that need extra caution
Do not draught-proof kitchens, bathrooms and utility rooms in the same way as living rooms and bedrooms. These rooms generate a lot of moisture, and they rely on ventilation to remove it. Internal doors to these rooms should also be left alone, so that air can circulate and extractor fans can do their job. The same applies to any room with an open fire, a flue or a gas heater: that room needs its air supply.
Watch for condensation after sealing
After draught-proofing, keep an eye on windows and cold corners for the first few weeks. A little condensation on a cold morning is normal, but persistent damp patches or mould growth mean the house is now too tightly sealed for its ventilation, and something needs to be reopened or improved. This is more likely in homes that already had damp problems, so if your home has a history of mould, tackle the ventilation first and the draught-proofing second.
What It Costs and What It Saves
Draught-proofing is unusual among home improvements because the cheapest version is also highly effective. A basic kit of self-adhesive strips, a door sweep, a letterbox brush and a tube of sealant typically costs less than a single month's heating bill for many households, and most of it can be fitted with nothing more than scissors, a screwdriver and a measuring tape.
For comparison, published Energy Saving Trust estimates for Great Britain put professional draught-proofing of windows and doors for a whole house at around £250, saving around £55 a year, and sealing an unused chimney at around £150 for the device, saving around £45 a year. Doing the work yourself cuts the cost sharply, though the saving stays roughly the same. Either way, the payback is measured in years, not decades, and the comfort improvement arrives on day one.
It is worth being honest about the limits. Draught-proofing reduces heat loss through gaps; it does not insulate walls, roofs or floors, and it will not fix a home that is cold because it has no insulation at all. Think of it as the first, cheapest layer of a warmer home, and the layer that makes every other improvement, from insulation to a new boiler, work better.
A Weekend Plan That Actually Gets Done
The job feels large until it is broken into a sequence. Here is a plan that fits a single weekend and leaves nothing half-finished.
Saturday morning: find and measure
Walk the house with the back of your hand and the tissue test, room by room, and write down every draught and its size. Measure the frames you plan to seal. Make a shopping list from those measurements, not from guesswork, and buy the strips, sweeps, sealant and any chimney device in one trip.
Saturday afternoon: doors and letterboxes
Start with external doors, because they give the biggest improvement for the least effort. Fit sweeps, frame strips, letterbox brushes and keyhole covers. Test every door after fitting: it should close and latch normally, with a slight resistance from the seal.
Sunday morning: windows
Work through the windows one room at a time, starting with the rooms you use most. Fit strips to casement windows and brush-pile strips to sash windows, leaving every trickle vent open. Test each window after fitting.
Sunday afternoon: floors, hatches and chimneys
Seal skirting-board gaps and floorboard gaps in the coldest rooms, fit a compression strip to the loft hatch, and install a chimney balloon or fireplace excluder in any genuinely unused fireplace, with a clear tag noting that the chimney is sealed. Walk the house once more with the tissue test and enjoy finding far fewer fluttering strips than you did on Saturday morning.
Seven Mistakes That Undo Good Draught-Proofing
One: sealing trickle vents, airbricks or gas appliance vents, which trades a draught for damp or danger. Two: fitting strips so thick that doors and windows will not close, which usually ends with the strip being ripped off. Three: sticking self-adhesive strips onto dusty, damp or greasy frames, so they peel off within weeks. Four: blocking a chimney that is still in use, or forgetting a chimney balloon is in place before lighting a fire. Five: draught-proofing kitchens and bathrooms as if they were living rooms, trapping moisture where it is generated. Six: filling floorboard gaps with rigid filler that cracks out as the boards move. Seven: doing the job in the wrong order, starting with the small gaps and running out of energy before reaching the doors and windows that matter most.
Frequently Asked Questions
Will draught-proofing make my home stuffy?
Not if it is done properly. Draught-proofing seals uncontrolled gaps, not deliberate ventilation. Trickle vents, airbricks and extractor fans stay open, so fresh air still circulates, just in a controlled way rather than through random cracks. If a room feels stuffy afterwards, check that a vent has not been blocked by accident.
Can I draught-proof a rented home?
Yes, and it is one of the best improvements a tenant can make, because most of it is reversible. Self-adhesive strips peel off, door sweeps unscrew, window film comes down, and chimney balloons deflate. Check your tenancy agreement first, and keep the original fittings so you can restore everything when you leave.
Is draught-proofing worth it if I already have double glazing?
Usually yes. Double glazing reduces heat loss through the glass, but draughts come through gaps in frames, doors, floors and lofts, which glazing does not address. Many double-glazed homes still have draughty front doors, unsealed loft hatches and gappy floorboards.
How long do draught-proofing materials last?
Foam strips typically last one to three years before they compress permanently. Rubber and silicone strips last considerably longer, often five years or more. Brush strips wear slowly and are easy to replace. Check your seals each autumn and replace anything flattened, torn or peeling, which is a ten-minute job once you know where everything is.
Should I hire a professional or do it myself?
Most draught-proofing is straightforward DIY, and doing it yourself saves most of the cost. Consider a professional for sash windows, which need precise fitting, for large or awkward gaps, or if you want a whole-house assessment that includes insulation advice. A professional can also confirm which vents must stay open, which is valuable in older homes with gas appliances.
Does draught-proofing help in summer too?
Yes, in a quieter way. The same gaps that leak warm air out in winter let hot air in during summer, and sealing them helps a home stay cooler on hot days, particularly when combined with shading and night-time ventilation. It also keeps out dust, pollen and insects, which is a bonus in any season.
The Bottom Line
Draught-proofing is not glamorous, and it will never be the subject of a glossy magazine spread. But few home improvements offer so much for so little: a weekend of work, a modest spend, warmer rooms from the first evening, and lower heating bills for years. November, with the cold now findable and the worst of winter still to come, is the moment to do it.
Start with the doors, work through the windows, finish with the floors, hatches and chimneys, and leave every deliberate vent exactly where it is. Do that, and the next time the heating comes on, the warmth will stay where it belongs: inside, with you.
