UK Home Insulation Guide 2026
Home Insulation UK 2026
The highest-ROI energy upgrade most UK homes can make, and the real fix for cold, damp rooms. Loft insulation pays back in 2–4 years. And if you qualify for ECO4, it could be completely free.
ECO4 closes 31 December 2026 — GBIS has already ended. ECO4 is your last chance for free insulation. Check eligibility now.
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Why Insulation Is the Best Energy Upgrade You Can Make
Around 25 million UK homes could be better insulated. Heating accounts for roughly 60% of the average energy bill — and a poorly insulated home leaks that heat through the roof, walls, floors, and gaps around windows and doors. You pay for every watt of it.
Insulation is also the essential first step before any other energy upgrade. Installing a heat pump or solar panels in a poorly insulated home is like filling a leaky bucket — you'll spend more and save less. Sort the insulation first. It's also the long-term fix for cold, damp and condensation-prone rooms: a dehumidifier or extra ventilation treats the symptom, but a consistently cold wall is usually the actual cause. We explain how the two work together in insulation, damp and condensation below.
The right order matters
Always insulate before upgrading your heating system. A well-insulated home needs a smaller heat pump, has lower running costs, and stays warmer for longer. Insulation first — everything else second.
Before you get insulation quotes, two changes cost nothing and often save more in the first year than loft insulation does: turning the boiler flow temperature down, and checking you're on the right tariff. They're the start of our energy efficiency bundle — six steps, ordered by how much you save per pound spent, using the system you already own. To see what insulation could save in your own home, try our insulation savings calculator.
Types of Home Insulation
Loft Insulation
25% of heat lost through roof · Fastest payback of any upgrade
Most UK lofts have 100mm of old fibreglass — the recommended level is 270mm. Topping up costs £400–£900 for a typical 3-bed home and saves around £250/year on heating bills. Payback in as little as 2 years. If you qualify for ECO4 it could be completely free. The simplest, cheapest, highest-return insulation upgrade available. When you top up, keep the eaves clear so air can still move through the roof, or you risk condensation in the loft.
Cavity Wall Insulation
33% of heat lost through walls · Saves up to £505/year
Homes built after the 1920s typically have a gap between inner and outer walls — the cavity. Filling it with insulation reduces heat loss by up to 33% and saves around £295/year on energy bills. The work takes a single day — contractors drill small holes, inject insulation material, and fill the holes. Most homeowners can't tell the work has been done afterwards. It isn't right for every wall, though: read what can go wrong with cavity wall insulation before you book.
Solid Wall Insulation
Older pre-1920s homes · Internal or external
Homes built before the 1920s typically have solid walls with no cavity. Insulation must be added to the inside or outside of the wall — a more expensive and disruptive process. External wall insulation changes the appearance of the property. Internal wall insulation is cheaper but reduces room sizes slightly. Saves up to £400/year. Solid-walled homes are also the most prone to cold-wall condensation and mould, so insulation often fixes a damp problem at the same time. ECO4 can fund this fully for eligible households — always seek grant funding before paying full price given the high cost.
Underfloor Insulation
10–15% of heat lost through floors
Relevant for homes with suspended timber floors — insulation is installed between the joists from below. Saves around £75–£150/year. Solid concrete floors can't be insulated from below. A useful addition after loft and wall insulation are done but not the priority for most homes.
Draught Proofing
Cheapest fix · Biggest impact per pound spent
Sealing gaps around windows, doors, letterboxes, and pipework is the cheapest energy upgrade available and delivers immediate results. Around £75–£350 professionally done — or much less DIY. Saves £75–£150/year. Should be done alongside or before any other insulation work. Don't block trickle vents, air bricks or extractor fans, though: a draught-proofed home still needs ventilation to keep condensation down.
Insulation Costs UK 2026
All costs include 0% VAT which currently applies to energy-saving insulation materials until March 2027.
| Type | Typical Cost | Annual Saving | Payback | Grant |
|---|---|---|---|---|
| Loft insulation | £400–£900 | ~£250/yr | 2–4 years | ECO4 |
| Cavity wall | £700–£3,500 | £230–£505/yr | 3–5 years | ECO4 |
| Solid wall (external) | £9,000–£22,000 | Up to £400/yr | 20–30 years | ECO4 |
| Solid wall (internal) | £8,000–£13,000 | Up to £400/yr | 15–25 years | ECO4 |
| Underfloor | £500–£2,000 | £75–£150/yr | 5–10 years | Sometimes |
| Draught proofing | £75–£350 | £75–£150/yr | 1–3 years | Rarely |
Full home insulation — 3-bed semi
A typical 3-bed semi getting loft insulation, cavity wall insulation and draught proofing costs around £2,000–£4,000 at full price and saves £450–£800/year. That's a 3–5 year payback. If you qualify for ECO4 the cost could be zero. Always check grants before paying anything.
Insulation Grants UK 2026
ECO4 Scheme
England, Scotland & Wales · Low income households
The Energy Company Obligation scheme requires large energy suppliers to fund insulation for eligible households. If you receive qualifying benefits or have a low income you can get insulation installed at zero cost. ECO4 was extended by 9 months to 31 December 2026 — there will be no ECO5. The Warm Homes Plan replaces it from 2027 but details are still emerging. Apply now while ECO4 is still guaranteed.
Qualifying benefits include:
Great British Insulation Scheme (GBIS)
Closed 31 March 2026 — no longer available
GBIS closed on 31 March 2026 and was not extended. If you were hoping to apply, ECO4 and the Warm Homes Local Grant are now the only routes for free or funded insulation. ECO4 closes December 2026 — check your eligibility now before it also ends.
Warm Homes: Local Grant
England · April 2025 – March 2028
Council-administered scheme running until March 2028. Provides grants for insulation and other energy efficiency measures for low-income households. Eligibility varies by local authority — contact your council or use the government's eligibility checker. This scheme will continue after ECO4 ends in December 2026.
Scotland & Wales Schemes
Home Energy Scotland · Nest Scheme Wales
Scotland: Home Energy Scotland offers grants and interest-free loans for insulation. Warmer Homes Scotland funds full cost for eligible lower-income households. Call 0808 808 2282. Wales: The Nest scheme provides fully funded improvements for households on low incomes or with certain health conditions.
Important: ECO4 closes 31 December 2026 and there will be no direct replacement. Some suppliers have already met their targets — funding is first-come, first-served. Processing takes 4–8 weeks, so with the scheme ending in December, apply now rather than waiting until the end of the year.
How Much Will You Save?
Savings vary significantly depending on your property size, current insulation levels, heating system, and how you use your home. The figures above are based on a typical 3-bed semi-detached house with gas central heating. Larger homes, oil-heated homes, and poorly insulated properties will save more. Get a figure for your own home with our insulation savings calculator.
Insulate before heat pump = smaller system, lower bills
A well-insulated home needs a smaller heat pump — reducing both installation cost and running costs. If you're planning a heat pump, insulating first can save £1,000–£3,000 on the heat pump itself and significantly reduce your annual running costs. See our Heat Pumps guide for more.
Insulation, Damp and Condensation
Most damp in UK homes is condensation: warm, moist air from cooking, showers and drying clothes indoors settling on the coldest surfaces in the room. In a poorly insulated home, those surfaces are external walls, ceilings under the loft and window reveals. That's where you see streaming windows, damp patches and black mould.
There are two ways to tackle it. A dehumidifier removes the moisture from the air, so there's less to condense. Insulation keeps the walls and ceilings warmer, so moisture doesn't settle on them in the first place. One works tonight; the other fixes the cause.
| Dehumidifier | Insulation | |
|---|---|---|
| Upfront cost | £150–£300 | £400–£3,500 for loft and cavity (often free under ECO4) |
| Running cost | ~4–9p an hour; roughly £50–£110 over a winter at 8 hours a day | None |
| Effect on your bills | Adds a little, though the heat it gives off isn't wasted in winter | Saves £250–£505 a year per measure |
| What it fixes | Moisture already in the air, including from washing | Cold surfaces where condensation forms |
| Best for | Fast results, renters, drying clothes indoors | Homeowners who want a permanent fix |
Our advice: use both
Run a dehumidifier this winter to get humidity under 60% and stop mould spreading, and get insulation sorted as the long-term fix, ideally through ECO4 while it's still open. Once walls and ceilings are warmer, the dehumidifier has much less work to do and you'll run it less. See our best dehumidifiers UK guide for picks from about 4p an hour.
Insulation won't fix every kind of damp. Tide marks low on a wall or patches that appear after rain point to rising or penetrating damp, which need the cause repairing first. Our guide to damp patches on walls helps you tell them apart, and condensation in your home covers the everyday fixes.
What Order Should You Insulate In?
Sorted by cost-per-pound-of-saving — do these in order for maximum return.
Draught proofing — £75–£350
Cheapest, fastest payback. Seal gaps around windows, doors, letterboxes and pipework. Do this first — it makes everything else more effective.
Loft insulation — £400–£900
25% of your heat escapes through the roof. Fastest payback of any significant insulation measure. Often free under ECO4 — check before paying.
Cavity wall insulation — £700–£3,500
33% of heat lost through walls. If your home was built after 1920 you almost certainly have cavity walls. Often free under ECO4.
Heat pump or solar — after insulating
Now your home is properly insulated you'll need a smaller heat pump with lower running costs. See our Heat Pumps and Solar Panels guides.
Underfloor & solid wall — if applicable
Worth doing but lower priority than loft and cavity wall. Solid wall insulation has a long payback at full price — always seek ECO4 funding first.
Home Insulation UK — Frequently Asked Questions
Last updated: 29 September 2026. ECO4 closes 31 December 2026 — figures and eligibility correct at time of writing but always confirm current status at gov.uk. Dehumidifier running costs use the October 2026 price cap of 26.32p/kWh.
Related Guides
Grants & next steps
Damp, condensation & mould
Check If You Qualify for Free Insulation
ECO4 closes 31 December 2026 and there is no replacement. Check eligibility now — processing takes 4–8 weeks so don't leave it too late.
Up to £14,000 of free insulation for eligible households.
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