Draught Proofing a Home Without Cutting Off Its Fresh Air

The clocks went back in the UK on Sunday, and the US and Canada follow on 1 November. It is dark by teatime now. The heating is coming on properly, and any house with a gap under the front door is about to make that gap known.

Forecasts for heating costs this winter are mixed. In the United States, homes heated with oil are expected to spend about a fifth more than last winter and homes heated with electricity about 4 percent more, while gas-heated homes should spend about 9 percent less. Whichever group your home falls into, warm air escaping through gaps you could close in an afternoon is heat you paid for and lost.

Draught proofing (drafts, if you spell it the American way) is one of the cheapest energy jobs in a home, and one of the few a renter can usually do alone. There is a catch, though. Some of the air moving through a house is supposed to be there. A home needs fresh air to stay dry, and anything that burns fuel needs air to burn safely. So the job has two halves. Close the accidental gaps, and leave the deliberate openings alone.

Pick a windy day or a cold evening with the heating on. Move slowly round each room with the back of a slightly damp hand, or a strip of tissue held between two fingers, and you will feel or see the air move. A curtain that sways when the window behind it is shut tells you the same thing from across the room.

Start with the obvious places. Window frames leak where the opening part meets the fixed frame, and old sliding sashes leak almost everywhere they slide. Outside doors leak along their edges and across the bottom, and through the letterbox and keyhole. Then look lower and higher. Gaps between floorboards and under skirting boards let cold air up from a suspended timber floor. Pipes and cables that pass through an outside wall often leave a ragged hole behind the boxing. The loft hatch is a classic, sitting loose in its frame directly above a warm landing. An unused open fireplace is an open chute to the sky.

Do the room you sit in longest first. If you work at home, that is probably the desk. A thin stream of cold air across your ankles barely registers when you are walking through a room, and after three hours of sitting still it is all you notice. A desk under a leaky window gets the worst of it, which is one more thing to weigh when you decide where the desk should go.

Before sealing anything, find the openings that exist on purpose. Many modern windows have trickle vents, slim slotted covers along the top of the frame. Older houses often have airbricks or grilles in the outside walls. Kitchens and bathrooms have extractor fans, or should. These are the home’s planned ventilation, and taping them over trades a slightly warmer room for condensation and, over a winter, mould.

Internal doors should not be draught proofed either. The gap under a bedroom or office door lets air move between rooms, and it is meant to be there.

Be most careful with anything that burns. A room with a gas fire, an open flue or an open fire may have a fixed vent that the appliance depends on for combustion air, and it must not be blocked. If a boiler, stove or fire burns fuel inside the house, leave its air supply exactly as it is, fit a carbon monoxide alarm if there isn’t one, and ask a qualified engineer before tightening that part of the home. The same goes for chimneys. A removable excluder in an unused flue is fine, as long as it comes out before anyone lights a fire.

There is also such a thing as a home that is tight enough already. If yours has no trickle vents, no wall vents and no mechanical ventilation, and you already see condensation on cold mornings, more sealing is the wrong job. Better ventilation comes first.

Self-adhesive foam strip is the cheapest option for opening windows and door edges. It compresses and wears out within a few seasons, but it is easy to fit, easy to replace and a reasonable choice for a rented flat you may leave next year. Brush strips and rubber or plastic wiper seals cost more and last longer. On sliding sash windows foam does a poor job, because the sash rubs it away, so brush strips are the usual answer, or a specialist for a big old sash in poor condition. A window that never opens can simply be sealed with clear silicone.

At an outside door, a brush or hinged flap excluder screws to the bottom edge and closes the biggest single gap in most hallways. A letterbox brush or inner flap deals with the next one; measure the opening before buying, since sizes vary. A keyhole cover with a drop-down metal disc costs very little.

Renters should check the lease before anything goes in with screws or permanent sealant. Adhesive foam can pull paint off when it comes away, so test a small piece somewhere hidden. Most of this kit is reversible in the same way a good rental home office is, which is the point.

None of this replaces insulation, and it will not fix a single-glazed window. Sealing gaps and topping up insulation together can cut a home’s annual energy bills by up to about a tenth, and the sealing part is the cheap end of that. Pick a cold evening, take a strip of tissue round the house, and buy the materials after you know where the air is getting in.