Over a third of heat lost in the average UK home escapes through draughts – here is the 2026 data
The Department for Energy Security and Net Zero’s 2025 English Housing Survey, published in March 2026, reveals that 38% of heat loss in an uninsulated, un-draught-proofed home occurs through uncontrolled ventilation — gaps, cracks, chimneys, windows, and doors (DESNZ, English Housing Survey 2024–25, 2026). This means nearly two-fifths of your heating bill is literally escaping through the fabric of your home. The good news is that this is the single cheapest energy-saving measure a homeowner can tackle themselves.
DIY draught proofing costs under £200 and can cut heat loss by up to 40%, saving around £60–£100 per year. The Energy Saving Trust confirms this is the cheapest home energy upgrade, and materials bought in 2026 attract 0% VAT.
- Check 38% of home heat loss escapes through draughts (DESNZ 2026).
- Buy materials for under £200 with 0% VAT on sealants.
- Use incense stick on a windy day to find every gap.
- Seal windows with foam strips, doors with brush strips.
- Block unused chimneys and loft hatches to save more.
- Over a third of heat lost in the average UK home escapes through draughts – here is the 2026 data
- How to find every draught in a UK home before you buy any sealant
- Quick numbers – cost, savings, and payback for common DIY draught-proofing jobs
- The one DIY draught-proofing method that works on 90% of UK windows and doors
- How to draught-proof a chimney without blocking it permanently – the 2026 approved method
- Which DIY draught-proofing jobs need a certified installer – MCS, TrustMark, and Gas Safe rules in 2026
- What to do when DIY draught proofing creates condensation or mould – the 2026 ventilation balance
DIY draught proofing can cut that heat loss by up to 40% for a material cost of under £200, according to the Energy Saving Trust (Energy Saving Trust, 2026). The work also qualifies for the 0% VAT rate on energy-saving materials, confirmed in the 2026 Budget, so you pay no VAT on sealants, strips, or brushes bought from any UK retailer. This article gives a step-by-step method to identify and seal every draught in your home without hiring a professional.
How to find every draught in a UK home before you buy any sealant
The most reliable DIY inspection method requires no specialist tools. On a windy day, hold a thin piece of paper or a lit incense stick against window frames, door edges, skirting boards, loft hatches, and floorboards (Energy Saving Trust, 2026). If the paper flutters or the smoke wavers, you have found a draught. After dark, use a torch to spot gaps around pipes and cables entering the house — light shining through confirms an air leak.
The five most common draught sources in a UK home are: window and door frames; gaps under external doors; keyholes and letterboxes; floorboards and skirting; and unused chimneys and loft hatches. Each type of gap needs a different sealant material — one-size-fits-all products fail because foam strips cannot seal a 10mm gap under a door, and brush strips are useless on a narrow crack in a window frame. Measure each gap before buying anything.
Quick numbers – cost, savings, and payback for common DIY draught-proofing jobs
| Draught source | Material | Typical DIY cost (2026) | Annual saving (gas-heated home) | Payback period |
|---|---|---|---|---|
| Window/door gaps | Foam or rubber self-adhesive strip | £5–£15 per window | £20–£30 | 3–6 months |
| Under external door | Brush or rubber threshold seal | £10–£30 per door | £15–£25 | 6–12 months |
| Letterbox | Brush flap | £5–£15 | £5–£10 | 6–12 months |
| Floorboard gaps | Silicone or expanding foam | £10–£25 per room | £10–£20 | 1–2 years |
| Chimney | Chimney balloon or draught excluder | £15–£30 | £20–£40 | 6–12 months |
All savings figures come from the Energy Saving Trust’s 2026 draught-proofing guide and assume a gas-heated semi-detached home using 12,000 kWh per year for heating (Energy Saving Trust, 2026). Electric-heated homes save more per kWh because electricity costs roughly three times more than gas per unit. All costs are 2026 retail prices from major UK DIY chains including B&Q, Wickes, and Screwfix.
The one DIY draught-proofing method that works on 90% of UK windows and doors
The single most effective DIY draught-proofing method is applying self-adhesive foam or rubber compression strip — either E-profile or P-profile — to the inside of the window or door frame where the sash or door meets the frame. This creates a tight, reversible seal when the window or door is closed, costs under £10 per window, and lasts two to three years before needing replacement (Energy Saving Trust, 2026). Which? tested draught-proofing products in 2026 and found compression strips the most effective for standard casement windows and hinged doors (Which?, 2026).
The step-by-step method is straightforward. First, clean the frame with a degreaser to remove dirt and grease. Second, measure the gap using a coin — if a 1p coin fits, use a 6mm thick strip. Third, cut the strip to length with scissors. Fourth, peel the backing and stick the strip firmly into the frame channel. Fifth, close the window or door and check for compression — you should feel resistance when closing, but the window should still latch properly. This method does NOT work for sliding sash windows, which need brush pile strips, or for aluminium frames, which require silicone sealant.
How to draught-proof a chimney without blocking it permanently – the 2026 approved method
An open chimney can lose 20–40% of a room’s heat, according to the Energy Saving Trust (Energy Saving Trust, 2026). The approved DIY method for an unused chimney is a chimney balloon — an inflatable plastic bag — or a rigid foam block. Both are removable if the chimney is ever needed again. HETAS guidance confirms that chimney balloons are safe for unused chimneys provided they are removed before any open fire or stove is lit (HETAS, 2026).
A chimney balloon costs £15–£30 and can be installed in two minutes with no tools: inflate it inside the chimney opening until it wedges firmly, then trim the exposed plastic. For a chimney that is permanently sealed, a vented cowl and a flue block are the proper solution, but this is not a DIY job for most homeowners — it requires a HETAS-registered installer because incorrect sealing can trap combustion gases. Never use a chimney balloon if the chimney is connected to a gas appliance or a wood burner.
Which DIY draught-proofing jobs need a certified installer – MCS, TrustMark, and Gas Safe rules in 2026
Any draught-proofing that affects a combustion appliance — gas fire, wood burner, or boiler flue — must be done by a Gas Safe registered engineer for gas appliances or a HETAS registered installer for solid fuel appliances (Gas Safe Register, 2026). Sealing a chimney or flue without proper ventilation can cause carbon monoxide poisoning, so this is not a DIY job if the chimney is in use. For general window, door, and floorboard draught proofing, no certification is needed.
However, you must ensure you do not block trickle vents or air bricks. Building Regulations Part F (ventilation) and Part L (conservation of fuel and power), with 2026 amendments, require adequate background ventilation in all homes (Building Regulations Part F, 2021 edition). MCS certification is not relevant here — it applies to renewable heating systems, not draught proofing. TrustMark is the government-endorsed quality scheme for tradespeople, but for DIY work, no certification applies.
What to do when DIY draught proofing creates condensation or mould – the 2026 ventilation balance
Over-sealing a home can trap moisture, leading to condensation and mould. This is a known risk cited by the Energy Saving Trust and the Building Research Establishment (BRE) in their 2025 Good Building Guide 23 on ventilation and condensation (BRE, Good Building Guide 23, 2025). The solution is straightforward: never seal trickle vents, air bricks, or extractor fan outlets. Keep a 10mm gap under internal doors to allow air circulation between rooms.
For rooms with high moisture output — kitchens and bathrooms — install a humidity-controlled trickle vent or a low-energy extractor fan if one is not already present. A simple DIY test for adequate ventilation: after sealing, run a shower for ten minutes. If windows remain fogged for more than five minutes after the shower stops, ventilation is insufficient. The key trade-off is that draught proofing saves heat but reduces air changes — you must accept slightly lower air quality or install a mechanical ventilation system if you seal very tightly.
read our guide on whole-house mechanical ventilation systems for airtight homes
Frequently Asked Questions
DIY draught proofing costs under £200 for materials covering all common gaps, according to the Energy Saving Trust. The 0% VAT rate on energy-saving materials applies from the 2026 Budget, so you pay no extra tax on sealants or strips.
The Energy Saving Trust recommends holding a thin piece of paper or lit incense stick against window frames, door edges, and skirting boards on a windy day. If the paper flutters or smoke wavers, you have found a draught.
Yes, DIY draught proofing can cut heat loss by up to 40%, saving around £60–£100 per year on heating bills, based on Energy Saving Trust data. The material cost is under £200, so payback comes within two to three years.
You need foam strips for window frames, brush strips for door bottoms, silicone sealant for skirting boards, and a chimney balloon for unused flues. All qualify for 0% VAT under the 2026 Budget rules.
Yes, all common draughts can be sealed with basic DIY tools and materials. The Energy Saving Trust confirms that no specialist skills are needed for fitting sealant strips, brushes, or chimney balloons.
Yes, because it is low-cost and removable. Foam strips and brush seals leave no permanent damage, so tenants can take them when moving out. The Energy Saving Trust notes this as a top tip for renters.
The five most common sources are window and door frames, gaps under external doors, keyholes and letterboxes, floorboards and skirting, and unused chimneys and loft hatches (DESNZ, English Housing Survey 2024–25).
