Home Insulation Costs UK 2026: Full Price Guide & Calculator

Home Insulation Costs UK 2026: The Full Breakdown

Heating accounts for roughly 60% of the average UK energy bill. A poorly insulated home leaks that heat through the roof, walls, floors, and gaps around windows and doors, and you pay for every watt of it. Insulation is worth doing, but be clear-eyed about the returns: on the Energy Saving Trust's own published costs and savings, most measures pay back over seven to eleven years, not two or three. It's a sound long-term investment in a thing that lasts decades. It is not a get-rich-quick scheme, and the sites telling you otherwise are usually quoting a saving against a cost from a different year.

This guide covers every major insulation type, what it actually costs in 2026 (including regional differences), what can go wrong, and which government schemes will pay for it.

Estimate Your Insulation Cost

Loft Insulation: £650–£1,200 Professional

What It Costs

If you're willing to do it yourself, mineral wool rolls cost £150–£400 in materials for a typical semi. The Energy Saving Trust's professional figures for Great Britain are £750 to insulate a bare loft to 270mm on a semi (£650 mid-terrace, £1,100 detached, £1,200 detached bungalow), and £600 to top up from 120mm to 270mm (£500 mid-terrace, £800 detached).

Building regulations require a minimum of 270mm. Many older UK homes have 100mm or less, so there's room to improve even if your loft was done decades ago. Note that the top-up is only about 20% cheaper than doing it from scratch, not half: you're paying for the same visit, the same access and most of the same material. That's the first hint that the two jobs are not equally worth it.

DIY or Professional?

Loft insulation is one of the few measures that's genuinely DIY-friendly. For a standard loft with boarded access:

• Materials: 6–8 rolls of 200mm mineral wool (to lay between joists) + 6–8 rolls of 100mm (to lay across joists). ~£200–£350 from B&Q or Wickes.
• Time: 4–6 hours for two people in a semi-detached loft
• What you need: Dust mask (FFP2 minimum, as mineral wool fibres are nasty), gloves, kneeling board, Stanley knife, torch. Don't stand between joists or you'll go through the ceiling.
• Common mistakes: Squashing insulation (reduces effectiveness), blocking eaves ventilation (causes condensation), burying electrical cables (fire risk; move them on top of the insulation)

If your loft is hard to access, has a flat roof, or you want to maintain a boarded storage area, get a professional. Our full loft insulation guide has a step-by-step DIY walkthrough.

Annual Savings

It depends entirely on what you're starting from, and the gap is enormous:

• Bare loft to 270mm: £140 a year on a mid-terrace, £190 on a semi, £350–£360 on a detached house or bungalow. Against £650–£1,200 professional, that's a three to five year payback, and under two years if you lay it yourself.
• 120mm to 270mm top-up: £13 a year on a mid-terrace, £17 on a semi, £35 on a detached. Against £500–£800 professional, that's 23 to 38 years.

So the folk wisdom that loft insulation is the fastest payback in the house is only true for a bare loft. If you already have a decent layer, topping it up is a comfort and heat-pump-sizing job, worth doing DIY for £200 of rolls, not worth paying a contractor £600 for on financial grounds alone. See our full loft insulation guide for the detail.

Grants

Loft insulation is widely covered by ECO4 and the Warm Homes: Local Grant. If you qualify, don't bother doing it yourself; let them pay for it and do it properly.

Cavity Wall Insulation: Around £2,200

What It Costs

The Energy Saving Trust puts a typical Great Britain installation at around £2,200, and about £1,000 in Northern Ireland. By house type: £950 a mid-floor flat, £1,100 a mid-terrace, £1,700 a detached bungalow, £2,200 a semi, £3,900 a detached house. In London and the South East, add 20–25%.

The work itself is quick. A contractor drills small holes (typically 22mm) in a pattern across the external brickwork, injects insulation under pressure, and fills and matches the holes. On an average home with easy access the Energy Saving Trust says it takes about two hours, and most homeowners can't tell afterwards.

Materials Used

Annual Savings

The Energy Saving Trust puts the saving at £110 a year on a mid-terrace or flat, £160 on a bungalow, £200 on a semi and £380 on a detached house. Set against its own cost figures, every house type lands at roughly a 9 to 11 year payback.

That's decent for something guaranteed for 25 years, and about a third of an uninsulated home's heat loss goes through the walls, so the comfort gain is real from the first winter. But it isn't the two-to-four-year payback you'll see quoted all over the web. Those numbers come from pairing a current saving with a cost from several years ago.

Is It Right for Your Home?

Cavity walls exist in most UK homes built between the 1920s and mid-1990s. If yours was built after ~1995, it almost certainly has insulation already (check your EPC). If it was built before the 1920s, you have solid walls, so skip to the solid wall section below.

Not sure? Look at the brickwork. If the bricks are all laid lengthways in a uniform pattern, you have a cavity wall. If you see a mix of headers (short ends) and stretchers (long sides), it's a solid wall.

When to Avoid It

Cavity wall insulation is not suitable if:

• Your walls face heavy, wind-driven rain: exposed west-facing walls in coastal areas are particularly risky. The insulation can act as a bridge for moisture.
• The cavity is under 50mm: not enough space to fill properly.
• There's existing damp: adding insulation to a damp wall makes it worse, not better. Fix the damp first.
• Previous injection has failed: removal costs £1,500–£4,000 and is messy. If a previous install has caused problems, get a specialist survey before trying again.

A proper pre-installation survey (which any reputable installer will do free of charge) should catch all of these. If an installer wants to skip the survey, find a different installer.

Grants

Cavity wall insulation is one of the most commonly grant-funded measures. ECO4, the Warm Homes: Local Grant (England), Home Energy Scotland, and the Nest scheme (Wales) can all cover the full cost for eligible households. See our full cavity wall insulation guide for detailed eligibility.

Draught Proofing: £100–£400

What It Costs

Draught proofing is the cheapest measure here. The Energy Saving Trust puts a professional job on the windows and doors of a whole house at around £250; DIY is £50–£150 in materials depending on how many doors and windows you tackle. It's also the fastest; a typical house can be draught-proofed in a day.

Where to Focus

• External doors: brush strips, foam seals, and letterbox covers. The front door is usually the worst offender.
• Windows: self-adhesive foam strips around opening sashes. Replace if crumbling.
• Skirting boards: fill gaps between skirting and floor with decorator's caulk. Takes 20 minutes per room.
• Loft hatch: strip of foam around the frame, draught excluder on the opening edge. Stops warm air leaking into the loft.
• Pipework and cables: any hole where a pipe or cable passes through a wall or floor. Fill with expanding foam or sealant.

See our best draught proofing products guide for specific recommendations, including our dedicated door draught excluder guide.

Annual Savings

The Energy Saving Trust puts draught proofing around windows, floors and doors at £55 a year in Great Britain (£80 in Northern Ireland), plus another £45 for blocking an open chimney you don't use (£60 in NI). So £55 to £100 a year depending on your fireplaces. Professional payback is four to five years; DIY is under two.

The real argument is comfort, and it compounds. A draught-free house is comfortable at a lower thermostat setting, and dropping from 22°C to 21°C saves another £120 a year on its own. That's the biggest single number on this page and it costs nothing, but you can only do it if the house isn't draughty.

Important: Don't seal everything. Every home needs ventilation. Never block air bricks, room vents (especially in rooms with gas appliances), or trickle vents in windows. If in doubt, ask an installer; sealing a gas boiler's ventilation is a safety issue, not just a comfort one.

Floor Insulation: £1,400–£2,500

What It Costs

Floor insulation applies mainly to ground floors with suspended timber construction, common in pre-1960s UK homes. The Energy Saving Trust puts a typical suspended floor installation at £1,400–£2,500 depending on house type and access to the underfloor void.

If there's a crawl space underneath, the installer can work from below without disturbing your flooring. If not, floorboards need lifting, which adds cost and disruption. Solid concrete floors can also be insulated, but that involves raising the floor level by 50–100mm, a much bigger job that's usually only done during a full renovation.

Annual Savings

The Energy Saving Trust puts floor insulation at around £55 a year in Great Britain (£70 in Northern Ireland). Against £1,400–£2,500 that's a 25 to 45 year payback, so let's be blunt: do not do this for the money. However, a cold floor is one of the biggest comfort complaints in older homes. If your floors feel cold underfoot even when the heating is on, floor insulation makes a noticeable difference to how the room feels, even if the energy savings are modest.

Material Options

• Mineral wool batts: fitted between joists, held up with netting. Cheapest option.
• Rigid PIR boards (Celotex/Kingspan): cut to fit between joists. Better thermal performance per mm. Our recommendation where access allows.
• Spray foam: quick to apply from below, but expensive and difficult to remove if problems arise. We'd avoid this for floors.

Solid Wall Insulation: £12,000–£15,000

This is the big one, and the reason many pre-1920s homeowners hesitate. Solid wall insulation is expensive and disruptive, but for a draughty Victorian or Edwardian home, it makes the single biggest difference to comfort and bills. The Energy Saving Trust's figures for a typical three-bedroom semi in Great Britain are around £12,000 internally and around £15,000 externally, for the whole house done in one go and fully redecorated afterwards in the internal case.

Internal Wall Insulation: Around £12,000

Insulated plasterboard is fixed to the interior face of external walls. Cost depends on how many walls, how many rooms, and how much remedial work is needed (moving radiators, extending window sills, refitting sockets and switches).

Pros: Cheaper than external. Can be done room by room over time. No planning permission needed. No scaffolding.

Cons: You lose 50–100mm of room depth on each wall. Skirting boards, coving, and sometimes flooring need refitting. It's disruptive; each room is effectively a small renovation project. There's a risk of interstitial condensation if not installed with a proper vapour barrier, which can cause hidden damp behind the insulation.

External Wall Insulation: Around £15,000

Insulation boards are fixed to the outside of the building and then rendered or clad. This is the more effective option (it wraps the house in a thermal blanket and eliminates cold bridges) but it's also the most expensive.

Pros: No loss of internal space. Better thermal performance. Eliminates cold bridges. Can completely transform the appearance of a tired-looking property. No disruption inside.

Cons: Requires scaffolding (4–6 weeks typically). Planning permission needed in conservation areas or for listed buildings. Can't easily be done on terraced houses if neighbours don't agree. Changes the external appearance; some people love it, others think it looks like a render job covering up problems.

Annual Savings and Payback

The two methods save much the same, because the wall ends up at a similar U-value either way. Energy Saving Trust figures for Great Britain: £140 a year for a mid-floor flat, £150 mid-terrace, £220 a detached bungalow, £280 a semi, £500 a detached house.

Do the division on a semi and it's stark. £12,000 internal against £280 a year is 43 years. £15,000 external is 54 years. Even a detached house at £500 a year takes about 30 years. That's longer than the insulation is guaranteed for.

This is why solid wall insulation almost always needs grant funding to make financial sense. It's a comfort-and-carbon decision more than a pure financial one, unless someone else is paying for it.

When It Makes Sense

• You qualify for ECO4 funding: this is by far the best scenario. Fully funded solid wall insulation is transformative.
• You're already renovating: if you're replastering, re-rendering, or reroofing, the marginal cost of adding insulation is much lower.
• You're planning a heat pump: solid wall insulation can reduce the size (and cost) of heat pump you need by 20–40%. It also means the heat pump runs more efficiently, cutting running costs for decades.
• Comfort matters more than payback: a solid-walled home in winter is genuinely cold, and insulation changes how the house feels. If you can afford it or get partial funding, the quality-of-life improvement is significant.

Regional Cost Differences

Every competitor on Google gives you a single UK-wide price range. In reality, what you pay varies significantly by region, mainly due to labour costs.

The Great British average row is the Energy Saving Trust's published figure; the others apply a labour adjustment to it, so treat them as indicative rather than quoted. Northern Ireland is a genuinely separate market with its own published numbers, and it's an odd one: cavity wall is far cheaper there, loft insulation is dearer. Material costs are broadly the same everywhere; it's labour that drives the difference. Our cost estimator above adjusts automatically based on your region.

What Can Go Wrong

Nobody else talks about this, but you should know before spending money:

Cavity Wall: Damp and Extraction Problems

Badly installed cavity wall insulation can cause damp, usually when the cavity is filled in a property that's exposed to driving rain (common on west-facing walls in Wales, Cornwall, and western Scotland). The insulation bridges the gap that was designed to keep water out. Signs of problems: damp patches appearing inside within 1–2 years of installation.

If this happens, the insulation needs extracting. Cost: £1,500–£4,000 depending on property size. It's covered by the CIGA 25-year guarantee if the original installer was registered, so keep your paperwork.

Internal Wall Insulation: Condensation Risk

If internal wall insulation isn't installed with a continuous vapour barrier, warm moist air from the room can reach the cold wall behind the insulation and condense there. You won't see it; it's hidden behind the plasterboard. Over years, this causes mould and rot in the wall structure.

The fix is simple: insist on a properly installed vapour control layer, and ensure the installer understands interstitial condensation. This isn't a reason to avoid internal insulation; it's a reason to use a qualified installer who knows what they're doing.

Loft Insulation: Condensation in Cold Lofts

When you insulate the loft floor, the loft space above gets colder (that's the point; you're keeping heat downstairs). A colder loft can mean more condensation on the underside of the roof. This is manageable if the loft has adequate ventilation: tile vents, soffit vents, or ridge vents. Problems occur when loft insulation is installed without checking ventilation first.

If your loft feels damp or you see black mould on the felt, get the ventilation sorted before adding more insulation.

Spray Foam: The One We'd Avoid

Spray foam insulation is heavily marketed online, but we'd recommend caution. It's difficult to remove, can mask structural problems in roofs, and many mortgage lenders won't accept properties with spray foam on the roof timbers. Several major lenders now flag it during surveys. If you ever want to sell, spray foam can complicate or delay the sale. Mineral wool is cheaper, proven, and doesn't cause lending issues.

Free Insulation Grants in 2026

ECO4 (Energy Company Obligation)

The biggest source of free insulation funding in Great Britain, and it's important to be precise about that: ECO is a Great Britain scheme, so it covers England, Scotland and Wales but not Northern Ireland. It's targeted at lower-income households receiving qualifying benefits (Universal Credit, Pension Credit, Child Tax Credit, and others). It funds the full cost of loft insulation, cavity wall insulation, and solid wall insulation, as well as heat pumps as part of a whole-house retrofit.

Ofgem's own page says ECO4 "will run until 31 December 2026, following a nine-month extension". No successor has been confirmed. If you qualify now, apply now; that's about three months away at the time of writing. Check eligibility via your energy supplier or an approved installer.

Warm Homes: Local Grant (England)

England only, and delivered through local councils. If you're eligible and your council still has funding, it arranges a survey and then organises and pays for the agreed work; you don't pay anything. Insulation, air source heat pumps, smart controls and solar can all be funded. gov.uk doesn't publish a cash cap per household, so ignore anyone quoting one, including the "up to £15,000" figure that circulates: what you get is whatever the survey recommends and your council agrees to fund.

To qualify your home must be in England, privately owned (by you or your landlord), and have an EPC of D, E, F or G. Household income must usually be £36,000 a year or less, though you may still qualify above that if you live in a designated postcode area or someone in the household receives certain benefits.

Great British Insulation Scheme (GBIS): Now Closed

GBIS was available to homeowners in council tax bands A–D in England (A–E in Scotland and Wales) with an EPC of D or below. It closed to new applications on 31 March 2026 with no direct successor announced. If you missed it, ECO4 (above) is the main remaining route to fully funded insulation until it closes on 31 December 2026, and the Warm Homes: Local Grant covers a wider income range in England. The Home Upgrade Grant (HUG2) is also closed, so ignore anyone offering that one too.

Home Energy Scotland

Scotland runs its own Home Energy Scotland Grant and Loan, open to homeowners regardless of benefits, which makes it much broader than ECO4. For energy efficiency measures such as insulation, the grant covers 75% of the combined cost up to a maximum grant of £7,500, with an optional interest-free loan for the rest.

The loan is capped per improvement, not at one big number, and the caps are lower than you might expect: £500 for loft, cavity or underfloor insulation, £1,000 for flat roof or room-in-roof, £2,500 for solid wall, £4,500 for insulated doors, £8,000 for glazing. The matching grant caps are £1,500 for loft, cavity or underfloor, £3,000 for flat roof or room-in-roof, and £7,500 for solid wall; glazing and insulated doors are loan-only. Rural and island homes get a £1,500 uplift, taking total possible grant funding to £18,000. Spray foam insulation isn't funded at all. Apply via Home Energy Scotland.

Nest (Wales)

Nest is the Welsh Government's scheme. It provides free impartial energy advice to anyone in Wales, and free home energy efficiency improvements (insulation, a heat pump, solar panels, and boiler or storage heater repairs where a home has no heating or hot water) to households that pass its eligibility check. There's no single published income threshold, so use the check rather than guessing. Start with the Nest page on gov.wales.

If you're also considering a heat pump, the Boiler Upgrade Scheme provides a separate £7,500 grant in England and Wales on top of any insulation funding, rising to £9,000 until 31 March 2027 if you're off the mains gas grid on oil or LPG. These grants stack: gov.uk confirms you're still eligible for BUS if you've already had funding to insulate the property. You can get free insulation and a subsidised heat pump.

Insulation Cost With and Without Grants

All figures are the Energy Saving Trust's for a gas-heated semi-detached house in Great Britain, with the payback worked out from those same two columns.

Read it and the strategy writes itself. Only two measures here pay back inside a decade if you fund them yourself: a bare loft and draught proofing. Everything else is either a comfort decision, a carbon decision, or a grant decision. If you qualify for ECO4 or the Warm Homes: Local Grant, all of it becomes worth doing immediately, because a 43-year payback and a free installation are very different propositions. Check eligibility before you commit to anything, and check it before 31 December 2026 when ECO4 closes.

Insulation and Heat Pumps: Why Order Matters

If you're considering a heat pump in the next few years, insulation should come first. Here's why:

• Smaller heat pump needed: a well-insulated home loses less heat, so you need a smaller (and cheaper) heat pump. Dropping a 1960s semi from a 12kW to a 7kW heat loss takes roughly £4,000–£5,000 off the installed price.
• Lower running costs: the fabric saving doesn't disappear when you change heating system. The £445 a year those three measures save a gas-heated semi becomes a slightly smaller cash saving on a heat pump, because heat pump heat currently costs less per kWh than gas heat, but the kilowatt-hours you stop needing are the same.
• Better comfort: heat pumps run at lower temperatures than gas boilers. In a poorly insulated home, this means rooms heat up slowly and may not reach target temperature on the coldest days. In a well-insulated home, the lower temperature works perfectly.
• Grants stack: you can get insulation funded through ECO4/WHLG and then claim the separate £7,500 BUS grant for the heat pump.

Read our full guide on insulating before getting a heat pump for the detailed order of operations.

Which Insulation Should You Do First?

The right order depends on your house. Here's what we'd recommend:

If You Have a 1920s–1990s Home (Cavity Walls)

This covers the majority of UK housing stock. Your priority order:

1. Loft insulation: go up with a tape measure first. Bare or under 100mm, get it to 270mm now, it's a four-year payback. Already at 120mm, the top-up is a 35-year payback, so do it yourself with £200 of rolls or leave it until you're doing something else up there.
2. Draught proofing: cheap, fast, and the comfort impact is immediate. Roughly a four-year payback on a professional job and under two on DIY, which beats everything except a bare loft. It also unlocks turning the thermostat down a degree, which is worth more than the draught proofing itself.
3. Cavity wall insulation: if not already done, this is the biggest single hole in the house, about a third of your heat loss. Around an 11-year payback if you pay for it, immediate if a grant does. Check your EPC; if it says "cavity wall: unfilled", you need this.
4. Floor insulation: if you have a suspended timber ground floor (common pre-1960s) and cold or draughty floors. Lower priority if your floors are concrete.

If You Have a Pre-1920s Home (Solid Walls)

Victorian and Edwardian homes are the hardest and most expensive to insulate, but they also have the most to gain:

1. Loft insulation: same as above. Always start here.
2. Draught proofing: older homes are typically draughtier than any other era. Original sash windows, gaps in floorboards, unused fireplaces: there's a lot to seal up.
3. Solid wall insulation: only if you can access ECO4 funding, you're already doing major renovation work, or you're planning a heat pump and need to reduce heat loss first. Without funding, the payback is simply too long for most people.
4. Floor insulation: original suspended timber floors in pre-1920s homes are often draughty. Insulating from below (if you have a crawl space) avoids lifting floorboards.

If You Have a Post-1995 Home

These should already have cavity wall and loft insulation, but it's worth checking. Your focus:

1. Check your loft insulation depth: even homes built to 1995–2005 regulations may only have 200mm. Topping up to 270mm won't pay for itself on the bill, so do it yourself with a couple of hundred pounds of rolls, or fold it into the prep if you're planning a heat pump.
2. Draught proofing: even newer homes develop gaps over time, especially around doors and windows.
3. Consider your windows: if you still have the original double glazing from the mid-1990s, it may be approaching end of life. Modern double or triple glazing is significantly better.

For all house types, don't overlook cheap wins like pipe insulation in your loft and garage (£15–£30 in materials, and mainly about not having a burst pipe in February), and thermal curtains if you have draughty or single-glazed windows.

How Long Does Insulation Last?

For the most part, insulation is a one-off investment. Loft insulation and cavity wall insulation done properly will outlast your mortgage. Draught proofing strips need occasional replacement, but they're cheap.

Summary

For most UK homeowners, the right approach is: a bare loft first (four-year payback, DIY-friendly), then draught proofing (cheap, immediate comfort, and it lets you turn the thermostat down a degree for another £120 a year), then cavity wall if applicable (about eleven years, but it's the biggest single heat loss in the house), then floors if the cold underfoot bothers you. A loft top-up from 120mm and solid wall insulation only make financial sense with grant funding, during major renovation, or as part of getting the house ready for a heat pump.

Before paying out of pocket for anything, check whether you qualify for ECO4, the Warm Homes: Local Grant, Home Energy Scotland, or Nest. Free insulation with immediate savings is the best deal in home energy.

If your windows are still single-glazed or original 1990s double glazing, replacement is a separate but related decision: it's a thermal upgrade rather than insulation strictly, with a much longer payback driven mostly by condensation, security and aesthetics. Worth costing alongside insulation, not instead of it.

Use our insulation savings calculator to model the costs and savings for your specific home, or try the estimator above to get a quick ballpark based on your house type and region.