Find the gaps before you buy a thing

Draughts are sneaky. On a still day you will feel nothing at all; on a blustery evening the same room feels like a tent. Before you spend a penny, spend twenty minutes hunting for the culprits. Pick a windy day, light a candle or a stick of incense, and move it slowly around the edges of your windows and doors, watching which way the smoke bends. If you would rather not wave a flame about near old timber, wet the back of your hand and run it around the frame instead — the cold patch is where the air is getting in.

Pay particular attention to the bottom of sash windows, the hinge side of doors, the junction between a door and its threshold, and any frame that has been painted so many times the gaps have been disguised rather than filled. Old buildings do not leak evenly, and it is usually two or three small offenders causing most of the misery.

Three workhorses: brushes, seals and excluders

Almost every job in a period property can be solved with one of three things, and all of them are reversible.

• Brushes — thin strips of bristle on a carrier, screwed or slid into a groove. They are the kindest option for sash windows and sliding mechanisms, because they allow movement while still blocking air.
• Seals — self-adhesive foam, rubber or silicone strips for surfaces that close against each other, such as casement windows and door frames. Choose EPDM or silicone over cheap foam if the frame faces the weather; foam goes brittle and crumbles within a season or two.
• Excluders — the physical barriers: brush strips that screw to the bottom of a door, threshold plates, letterbox brushes, keyhole covers and chimney draught excluders. These do the heavy lifting at ground and roof level.

Keep the packaging and the offcuts. If a strip proves too thick and stops a window closing, you will want to swap it for a slimmer profile rather than force the frame.

Windows: sash, casement and the sneaky gaps

Sash windows are notorious, but they are also straightforward to improve. The main offenders are the meeting rails in the middle, the sides where the sashes slide in their staff beads, and the bottom rail where the two sashes overlap.

• Fit brush pile into the staff beads so the sashes can still run freely.
• Add a slim brush or foam seal at the meeting rail, checking that the sashes still close flush.
• For the bottom of the lower sash, a shallow sash seal or a discreet length of brush strip closes the largest single gap in many old houses.
• Check the outer frame joinery for gaps where the architrave meets the wall, and run a thin bead of decorator's caulk there rather than sealant.

Casement windows are easier still. Clean the frame, let it dry, then apply a self-adhesive seal along the closing face — not the hinge side, which will simply push the window off square. On metal frames, use a silicone seal rather than foam, as condensation will destroy anything porous.

If your home is listed, or sits within a conservation area, remember that any fixings into historic fabric may need consent. Stick-on and screw-on solutions that leave no lasting mark are your friends here; keep them neat and in keeping with the frame colour.

Doors: the biggest offenders

A gap of just a few millimetres along the bottom of a door can move a surprising volume of air. Front and back doors usually need a combination of measures.

• Bottom of the door: a screw-fixed brush strip is the standard answer. On uneven old floors, a hinged or drop-down excluder that lifts as the door opens works better.
• Sides and top: a brush or rubber seal in the rebate, or a face-fixed strip on the frame if the door is too tight to take a rebate.
• Letterbox: a brush flap inside and out, plus a slim seal around the plate.
• Keyhole: a small covered escutcheon or a magnetic cover — a tiny gap that produces a surprisingly fierce draught.
• Threshold: where there is a real gap under the door, a threshold plate or a shaped timber bar will do more than any amount of sealant.

Internal doors matter too, especially between a heated living room and a cold hallway. Soft draught excluders — the old-fashioned sausage variety — are still perfectly good, and they do no harm at all.

Let the house breathe while you seal it

Older properties are not sealed boxes; they manage moisture by breathing. If you block every gap and switch off the ventilation, you will trade draughts for condensation, damp patches and mould on cold external walls.

• Keep trickle vents open, or leave one small window on a latch in bathrooms and kitchens.
• Never seal a room that contains an open fire or a gas appliance without a permanent, unobstructed air supply.
• Keep chimney draught excluders out when a fire is lit, and use them only on unused flues.
• After a week or two, look for misted windows, damp corners or a musty smell — those are the signs to let a little air back in.

A weekend's work, room by room

Start where you sit. Draught proof the living room windows and the door to the hall first, then work through bedrooms, and finish with the front and back doors. Do one room at a time, test each window and door as you go, and you will feel the difference immediately: warmer floors, fewer chills around the ankles, and a house that holds its heat without losing any of its character.