October 10, 2026
Old houses are generous with air. A sash window that rattles in a northeasterly, floorboards you can see daylight through, a chimney that pulls like a funnel: charming in June, punishing in January. The aim isn't to seal the place into a plastic box. It's to slow the air where it chills you, while leaving enough movement through the building to keep timber, plaster and stone dry.
Take it room by room, and start where you feel the cold most.
Doors: the quickest wins
Most heat leaves through the doors you use every day, so the front and back doors are worth an hour of your time. Before buying a single strip of seal, check the door still fits its frame. One that has dropped on its hinges or swollen with damp will hold a gap at a corner no matter how much foam tape you press on. Adjust the hinges or plane the edge first, then deal with the edges.
- Under the door. A brush strip or rubber squeegee blade fixed to the inside face; a fabric draught excluder works well on internal doors you only use occasionally.
- The frame. A seal carrier screwed to the doorstop with a rubber or brush gasket lasts far longer than self-adhesive foam, which flattens within a season.
- Letterbox and keyhole. A brush flap with a weather seal behind it, plus a covered keyhole plate. Small money, noticeable difference.
- The threshold. If there's a step down to the outside, a raised threshold bar with a seal closes gaps nothing else will reach.
A curtain on a rail across the front door does more than it looks, especially in a lobby or hallway. If you have the space, a porch or an inner door creates an airlock: two doors never open at once, and the draught never reaches the hall.
Windows: sash, casement and everything in between
A traditional sash window leaks in three places — where the two sashes meet in the middle, where they slide in their channels, and where the frame meets the wall. Each needs a different answer.
Sash windows
For the channels, brush or sprung-metal strips fitted into the parting beads let the sash slide but block the draught. At the meeting rails, a strip of brush seal on the inner face of the lower sash closes the gap when the window is shut and the fastener is tight. Around the frame, a bead of decorator's caulk or a low-modulus sealant handles the gap between timber and plaster — use something flexible, because both will move with the seasons.
Casement windows
Casements usually need a compression seal set into the rebate, rather than brushes. Check the handles and stays as well: if the latch doesn't pull the opening edge firmly against the frame, no seal will do its job. A few minutes with a screwdriver on a slack hinge often solves more than a trip to the shop.
Curtains and secondary glazing
Heavy curtains with a thermal lining, hung from a track that overlaps the window edges, cut the chill that radiates off cold glass. A simple pelmet or valance across the top makes a surprising difference, because warm air otherwise slips up behind the curtain and straight out through the gap. Secondary glazing — a slim pane fixed inside the reveal with magnetic tape or a light frame — is genuinely effective on single glazing and is reversible, which matters in rented flats and listed buildings. Whatever you fit, never cover a trickle vent.
Floorboards, skirting and airbricks
Gaps between floorboards in an old house can add up to an open window's worth of cold air. Fill them with something that moves. Rigid filler cracks and crumbles as the boards expand and contract; a foam backer rod pushed into the gap with a bead of flexible acrylic or low-modulus sealant over the top will last. On a visible floor, narrow slivers of matching timber glued in and planed flush look better and take stain.
Where the skirting meets the wall — and where the floor meets the skirting — run a thin bead of decorator's caulk. It's fiddly work, best done a metre at a time with a damp cloth in the other hand, but it stops the cold creep that makes a room feel restless.
One firm caution about airbricks. If your ground floor is suspended timber, the airbricks in the outside walls ventilate the void underneath and keep the joists dry. Blocking them to stop a draught is how you start a rot problem. Fit baffled airbrick covers instead: they cut the blast while keeping the air moving.
Chimneys and fireplaces
An open flue is a hole in the roof as far as warm air is concerned. If the fireplace is genuinely disused and will stay that way, a chimney balloon, a purpose-made wool draught excluder or a removable board across the opening will make an immediate difference. A cowl on the pot outside keeps rain and downdraughts out at the same time.
The rule is simple: never block the flue or the room ventilation serving a working appliance. Boilers, gas fires, wood burners and open fires all need theirs. Even a disused flue should keep a small path for air — most chimney balloons have a vent built in, and a permanent vent in a register plate does the same job. A completely sealed, cold flue gathers condensation, which stains the chimney breast and leaves a sour smell in the room.
Draught-proofing without making damp
Older British houses were built to breathe. Lime plaster and solid walls absorb and release moisture; suspended floors and open flues move air through the building. Cooking, washing, drying laundry and simply breathing add several litres of water vapour to the air every day. If every gap is sealed, that moisture has nowhere to go. It finds the nearest cold surface — a window reveal, an outside wall corner, the back of a wardrobe — and turns into condensation, then mould.
So aim for draughts, not background ventilation. Leave these alone:
- Trickle vents in windows and any fixed wall vent.
- Airbricks, particularly those serving a suspended floor or a chimney.
- Extract fans in kitchens and bathrooms, and any window relied on for ventilation there.
- Flues, air vents and grilles serving gas, oil or solid fuel appliances.
- Eaves and loft ventilation at the roof edge.
Ventilation for a gas appliance is a safety matter, not a comfort one. Gas work and flue checks belong with a Gas Safe registered engineer, and solid fuel appliances with a suitably qualified installer. If you already have mould, a musty smell or damp patches, find the cause before sealing anything else, and take advice from a qualified damp specialist if it keeps returning.
Finding the draughts, then working from the coldest room out
On a windy day, walk round with the back of your hand near frames, skirting and flues, or hold a sliver of tissue and watch it flutter. Mark what you find, then work in this order:
- Front and back doors, plus letterboxes and thresholds.
- Windows in the rooms you use most.
- Floorboards and skirting, working away from the outside walls.
- Chimneys and fireplaces, once you've confirmed nothing is in use.
- Curtains, linings and pelmets as a final layer.
Start with the cheap, reversible things — seals, excluders, a door curtain — and live with them for a fortnight before spending more. Check your work again in midwinter, when timber shrinks and rubber compresses; a ten-minute adjustment in January is often all that's needed.
And know when to stop. A house that's warm but still breathes a little is a far better result than one that's airtight and damp. If a chimney, a flue or a patch of damp leaves you guessing, get someone qualified to look — that's money well spent, and it keeps the rest of your good work from causing trouble.
Photo: falco / Pixabay
