Draught-proofing on a budget: which cheap fixes make the biggest difference?

The cheapest draught-proofing fixes, such as sealing gaps around doors, windows, floorboards and the letterbox, are DIY jobs that most people can finish in an afternoon. They stop warm air leaking out and cold air coming in, so your heating has less work to do.

The biggest difference usually comes from the gaps you can feel or see daylight through. Start there, and leave the ventilation you need alone. I'll cover both below, with a worked saving at today's gas price so you can see what a job like this is worth.

Find the draughts first

Before you buy anything, spend ten minutes finding where the air is getting in. It stops you spending money on the wrong job.

1. Pick a cold, breezy day and shut all the windows and doors.
2. Hold your hand near the edges of windows and doors, the letterbox, keyholes, and where skirting boards meet the floor. Cold moving air is easy to feel.
3. Use a candle or incense stick held near the same spots (carefully, away from curtains). If the smoke or flame flickers sideways, there's a gap.
4. Look from outside at night with a light on inside. Daylight or lamplight showing through a door edge is a gap.

Write the worst spots down. That's your shopping list.

The cheap fixes, in the order I'd do them

These are all DIY, and none needs a tradesperson.

1. Door and window seals. Self-adhesive foam or rubber strip along the frame, where the door or window closes, is cheap and quick. Measure first, and clean the surface so it sticks.
2. A draught excluder at the bottom of external doors. A brush or rubber strip fixed to the base of the door, or a fabric excluder on the floor, blocks the gap you can often see under the door.
3. Letterbox and keyhole covers. A brush or flap on the letterbox and a cover on the keyhole deal with two small gaps that let in a surprising amount of cold air.
4. Gaps between floorboards and skirting. Flexible filler or sealant along the skirting edge, and strips or filler for gaps in floorboards, stop air coming up from underneath.
5. Sealant around window frames. Where the frame meets the wall, a bead of caulk or sealant fills small cracks.

I haven't quoted prices because they vary by shop and by size. Look at the price on the shelf before you decide, and buy for the worst spots first.

What it might save you: a worked example

I don't have a trustworthy, up-to-date source for what a typical draught-proofing job saves in pounds, and the figures online date from different price levels. So here's a worked example you can redo with your own numbers, and the assumptions are mine.

On 24 October 2026, the Flexible Octopus gas rate in London was about 8.1p per kWh including VAT (from the Octopus Energy API). Your region will be close, and your bill has your exact rate.

Say your home uses 10,000kWh of gas a year for heating. That's about £815 at 8.1p. If draught-proofing cuts your heating use by 5% to 10%, which is my assumption for a draughty home and not a measured figure, the saving looks like this:

Gas used for heating in a year	Heating cost at 8.1p	Saving at 5%	Saving at 10%
6,000kWh (small flat)	about £489	about £24	about £49
10,000kWh (typical house)	about £815	about £41	about £82
14,000kWh (larger or leakier home)	about £1,141	about £57	about £114

Treat these as an illustration. A home with big gaps could save more, and a home that's already snug will save less. Even so, a few pounds of seal and an afternoon is a good return if you land anywhere near the low end.

The same thinking applies to turning the dial down: I did a similar sum in does turning your thermostat down by 1°C really save money. Doing both stacks the effect, because a home that holds its heat is also easier to keep comfortable at a slightly lower setting.

Don't seal up the ventilation you need

This is the part not to skip. Some gaps are there on purpose. Your home needs fresh air so that gas boilers, fires and cookers burn safely, and so damp and mould don't build up.

The NHS says carbon monoxide can come from appliances that are faulty, badly installed or poorly maintained, and advises you to keep rooms well ventilated and make sure chimneys and flues are clean and well maintained. So:

• Leave trickle vents, air bricks and extractor fans alone. Don't block or seal them.
• Don't seal around a chimney or flue for an open fire or a gas appliance that draws air from the room.
• Keep a carbon monoxide alarm in rooms with a gas or solid fuel appliance, and have boilers and heaters serviced regularly by a qualified, registered engineer.
• Watch for damp. If you start getting condensation or mould after sealing up, you've probably cut off ventilation somewhere, so open a window for a few minutes a day or run the bathroom and kitchen extractors.

If you're not sure whether a gap is there for ventilation, leave it and ask a heating engineer.

Where to start this weekend

If you want a short plan:

1. Do the hand and candle test and write down the five worst gaps.
2. Seal the external doors first (bottom strip, letterbox, keyhole).
3. Move on to window edges and skirting boards.
4. Leave vents, flues and extractor fans exactly as they are.

Then see how the house feels, and keep an eye on your gas use over the next few weeks. The Gas or electric? tool lets you put in your own prices and heating use, so you can see what each unit of heat costs you and what a few percent is worth.

The short version

• Find the draughts first with the hand and candle test, then fix the worst ones.
• Door, letterbox, window and skirting seals are cheap DIY jobs that need no tradesperson.
• At 8.1p per kWh, a typical house using 10,000kWh for heating might save roughly £41 to £82 a year if draught-proofing cuts use by 5% to 10% (my assumption, not a measurement).
• Never block vents, flues or extractor fans, and keep a carbon monoxide alarm.

This weekend, spend ten minutes on the hand test. You'll probably find the worst gap before you've finished your tea.