Draught-Proofing a Rented Flat

Find the draught before buying anything for it. The window is the usual suspect and frequently innocent: cold glass chills air that then falls and crosses the floor, which feels identical to a draught and is not one. Sealing the frame does nothing for it.

A lit candle walked slowly around frames, the letterbox, the loft hatch and the skirting will tell you in ten minutes what the right purchase is. In most flats the answer is the front door.

A note on this guide: this rests on how air moves through a building and on manufacturers' stated application conditions, not on measurements taken here. See how we test.

The problem, as it appears

A room that will not hold heat. A cold band across the floor. A particular chair that is always colder than the rest of the room. And a tenancy agreement that rules out doing anything permanent about it.

The instinctive response — heavier curtains, and turning the heating up — treats the symptom at the point where it is felt rather than where it is caused.

Why the obvious fix disappoints

The obvious fix is to seal the windows, and it disappoints for two reasons.

First, the window often is not the source. Air enters a flat wherever there is a hole and a pressure difference: under the front door, through the letterbox, around the keyhole, at the loft hatch, behind skirting boards, and where pipes and cables pass through walls. Those are unglamorous and they add up to far more area than a window seal.

Second, cold glass is not a draught. Air in contact with a cold pane loses heat, becomes denser, and falls. It then travels across the floor as a cold current that behaves exactly like air coming in from outside. Tape around the frame does nothing about it, because nothing is coming in.

Distinguishing the two takes a candle and ten minutes, and it decides which product is worth buying.

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What actually matters

1. Where the air genuinely moves

Close every external window and door first, then walk the room with a lit candle or an incense stick held near every edge and joint. Where the smoke bends, air is moving. Where it rises straight, it is not.

Do the front door last, because it is usually the largest single source and it will otherwise dominate everything else you test.

2. Which gaps are faults and which are design

Do not block trickle vents or wall vents. They are there to control condensation, and where any appliance burns fuel they supply combustion air. Sealing them trades a cold room for a damp one, or for something considerably more serious.

The gaps worth closing are the ones nobody designed: a worn door seal, an unbrushed letterbox, a gap where a pipe enters the wall.

3. Whether it comes off cleanly

Everything here has to be reversible. Self-adhesive seal on old gloss paintwork is the main risk — test on a hidden section of the frame, and at the end of the tenancy remove slowly rather than pulling.

The options, and who each suits

The front door, first

The gap under it, the letterbox and the keyhole together usually move more air than every window in the flat. All three are fixable in under an hour with nothing permanent.

Self-adhesive seal on frames

For doors and casement windows that no longer close tightly, and for a draughty loft hatch. Cheap, quick, and it works on the gaps a candle actually finds.

There is a second reason to seal the same gap, and in a flat it is often the bigger one. Airborne noise from a shared hallway travels through the gap around a door rather than through the door itself, which is why a solid front door can still let in every conversation outside it.

The acoustic versions of the same seal are heavier and denser, because mass is what stops sound where a thin foam strip only stops air. Expect a noticeable improvement rather than silence: sealing the perimeter addresses the leak, not the wall.

Window insulation film

The fix for cold glass rather than for moving air, and it is the right answer to the falling-air problem that feels like a draught.

It traps a still layer against the pane, which is what double glazing does with a bigger gap. It looks slightly odd in direct light, and on single glazing the difference is noticeable.

The mistake to avoid

Sealing everything, including the vents. A flat needs air changes. Moisture from cooking, washing, drying clothes and breathing has to leave, and in a well-sealed flat with the vents blocked it condenses on the coldest surface instead — which becomes mould in the corners of external walls, usually behind furniture where it is found late.

The goal is not an airtight flat. It is closing the gaps nobody intended while leaving the ones somebody did.

The second mistake is sealing a draught that is a reportable defect. A rotten frame, a failed extractor backdraught flap or a door that no longer closes is a repair, and repairs are the landlord's. Tape over it and you have quietly taken on the problem.

Once the flat holds its heat, the floor is usually the next thing that feels wrong — covering a rental floor you cannot change deals with that, and hanging things without drilling covers heavier curtains if that is where you land.