Last reviewed: 16 April 2026By Eco Home Check Editorial Team
Loft insulation costs £300 to £600 for a typical three-bedroom house and cuts heating bills by around 25%. If your home has less than 100mm of insulation up there, or none at all, this is the single most cost-effective energy upgrade you can make. ECO4 funds it completely for eligible households. Here's everything you need to know before you start.
What Loft Insulation Costs in 2026
£300 to £600. That's the range for a professional mineral wool install on a typical three-bed semi, based on Energy Saving Trust figures. DIY the same job with rolls from B&Q or Wickes and you're looking at £150 to £300 in materials.
Blown fibre, where insulation gets blown into the loft through a hose, runs £500 to £800. It's faster for contractors and handles awkward joist spacing well, but you're paying for the machine time and the specialist labour. Rigid foam boards (PIR or phenolic, brand names Celotex and Kingspan) cost £800 to £1,500 but only come into play for loft conversions where you're insulating between rafters rather than on the floor.
What swings the price: house size, access, the depth of any existing insulation, and where you live. A ground-floor hatch with a pull-down ladder is a two-hour job. A loft with a scuttle hole over the stairs, three-quarters boarded and crammed with stored boxes, is closer to a full morning. London and the South East add roughly 10% to 20% on top of national averages.
One thing to factor in when you're comparing quotes: a decent installer will include disposal of the old compressed stuff, lagging for any exposed pipework, and a 25-year guarantee through a scheme like the National Insulation Association. Cheaper quotes often strip these out. Ask what's included before you judge a number.
Per square metre, you're looking at £5 to £12 installed. Here's the honest truth about DIY: mineral wool is one of the few energy upgrades that's genuinely simple to lay yourself. If you can walk around safely in your loft, you can do it. The main rules are don't compress it and don't cover the eaves.
Which Type to Choose
Right, so what's actually up there making the difference?
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Grant amounts and eligibility criteria are based on publicly available government data and may change. Always verify current terms directly with the scheme provider.
Frequently asked questions
How much does loft insulation cost in 2026?
£300 to £600 for a professional mineral wool installation on a typical three-bedroom house, based on Energy Saving Trust figures. DIY with rolls from B&Q or Wickes costs £150 to £300 in materials.
Can I get free loft insulation?
Yes, through ECO4 if someone in the household receives qualifying benefits like Universal Credit or Pension Credit and your home has an EPC rating of D or below. Warm Homes: Local Grant may also cover it depending on your council and household income (usually under £36,000). About a third of UK households meet ECO4 criteria, so it's always worth checking before you pay. ECO4 runs until December 2026 and covers the full cost including labour and materials.
How thick should loft insulation be?
270mm of mineral wool is the building regulations target for most homes.
Is loft insulation worth it?
For almost any home with less than 100mm currently up there, yes. A typical install costs £300 and saves around £250 a year, which means it pays for itself in about 14 months. No other energy upgrade comes close to that payback period. Every year after that is a return on the original outlay.
Can I install loft insulation myself?
Yes, for mineral wool rolls in a standard loft with decent hatch access. Blown fibre needs specialist equipment and rigid board in conversions needs building regs sign-off, so those are professional-only jobs.
Check if you qualify
Answer a few quick questions to see which government energy grants you're eligible for. Free, instant results.
Mineral wool (glass wool or rock wool) is what goes in 90% of UK lofts. It's cheap, effective, and any installer in the country will fit it without blinking. Knauf, Isover and Rockwool are the three big brands and they're broadly interchangeable at the performance level. It comes in 100mm and 170mm rolls, and the standard approach is 100mm between the joists with another 170mm laid across the top at right angles. Total depth: 270mm. That's what building regs are aiming at.
For a standard loft that you're not converting, mineral wool is the obvious choice. It's cheap, effective, and your surveyor won't bat an eyelid.
Blown fibre is loose cellulose or mineral wool blown in through a hose. The installer pushes the nozzle through the hatch and fills the loft until the stated depth is reached. It works well for awkward layouts: irregular joist spacing, tight eaves, chopped-up roof spaces with lots of obstacles. It's slightly more expensive than rolls (£500 to £800 installed) but faster for contractors, which is why ECO4 suppliers often fit it. Downside: once it's down, walking on it compresses it, so you can't board over the top without raising the floor level first.
Is blown fibre better than DIY mineral wool? Honestly, it depends on your loft. If you've got clear joists and decent access, rolls are cheaper and just as effective. If your loft is a cat's cradle of cables, pipes, irregular framing and low headroom, blown fibre is worth the extra money.
Rigid foam boards (Celotex, Kingspan) belong in loft conversions, not standard lofts. You fit them between the rafters rather than on the floor, because the point is to keep heat inside the new habitable room below the roof. They have a higher R-value per millimetre than mineral wool (roughly double), but they cost several times more and need careful detailing. If you're converting the loft, your builder will handle this. If you're just insulating a cold loft for the first time, skip them.
Spray foam works. That's the honest assessment. Properly installed open-cell spray foam does insulate a loft effectively. The problem is mortgage lenders: a growing number of high-street lenders now refuse to lend on houses with spray foam in the loft because of roof ventilation and moisture concerns, which makes your house harder to sell later. Read our spray foam insulation guide before you consider it. For a standard loft, don't.
Sheep wool and recycled alternatives (hemp, recycled plastic bottles) are the eco options. Thermafleece and Termolan are the brands you'll see. Performance is broadly similar to mineral wool at roughly 10% to 20% higher cost, and they're pleasant to handle with no itchy fibres. If your budget is stretched, mineral wool does the same job. If you're set on avoiding synthetic insulation or you care about embodied carbon, they're a defensible choice.
How Thick Should Loft Insulation Be?
270mm of mineral wool. That's the target.
If you already have 100mm up there (a single layer, often laid when the house was built in the 1980s), add another 170mm roll across the top at right angles to the joists. Between-joist plus over-joist is how you get to the full depth without squashing anything. If you've got nothing up there at all, lay 100mm between the joists and 170mm over the top. Job done.
The diminishing returns matter here. Going from 0mm to 270mm saves roughly £250 a year on heating bills for a typical three-bed, according to Energy Saving Trust figures. Going from 270mm to 400mm saves around £20 a year. Don't bother. You've already captured nearly all the benefit at the building regs target.
Current depth
Action needed
Approximate cost
None
Full 270mm install
£300 to £600
Under 100mm
Top up to 270mm
£200 to £400
100mm to 150mm
Top-up layer
£150 to £300
270mm or more
Nothing, you're done
£0
Once the loft is sorted, cavity wall insulation is usually the next upgrade worth looking at if your walls have an unfilled cavity. The payback is even faster.
Grants That Fund Loft Insulation
ECO4 is the main route. If someone in the household receives qualifying benefits (Universal Credit, Pension Credit, Child Tax Credit, Income Support, JSA or ESA) and your home has an EPC rating of D or below, your energy supplier could fund the entire loft insulation job at no cost, according to GOV.UK. Mineral wool and blown fibre both qualify. The scheme covers the whole installation: contractor labour, materials and the standard 25-year guarantee. Loft insulation is one of the most commonly delivered measures under ECO4 because it's cheap for suppliers to fund and delivers a solid SAP improvement. The scheme is administered by Ofgem and delivered through the major energy suppliers. ECO4 runs until December 2026.
If there's any chance you qualify for ECO4, check before paying out of pocket. About a third of UK households meet the criteria. Most never look into it.
Warm Homes: Local Grant varies by council. Some authorities fund loft insulation directly, others focus on different measures. Household income usually needs to be under £36,000 and the property typically needs an EPC of D or below, though specific criteria differ by area. You apply through your council rather than through an energy supplier, which means the process and timing is different from ECO4.
GBIS (Great British Insulation Scheme) closed in March 2026. It previously funded loft insulation for homes in council tax bands A to D, but it's no longer accepting applications. Older guides still reference it, so worth knowing it's gone.
0% VAT applies to professional installations until March 2027. If you're paying out of pocket and using a contractor, the installation should be zero-rated rather than charged at 20%. The relief doesn't apply to rolls you buy yourself for DIY fitting.
Can You DIY Loft Insulation?
Yes. Mineral wool rolls in a standard, accessible loft are one of the few energy upgrades that's genuinely DIY-able.
What you need: mineral wool rolls (100mm and 170mm), a Stanley knife or long bread knife for cutting, an FFP2 dust mask, safety goggles, long sleeves and gloves. Boarding is optional if you want storage on top. Rolls cost £5 to £8 per square metre at B&Q, Wickes or Screwfix.
The order matters. Start at the furthest point from the hatch and work backwards, otherwise you'll end up trampling freshly laid insulation on your way out. Lay the 100mm between the joists first, tight to the edges but not compressed. Then lay the 170mm perpendicular across the top, covering the joists themselves. Don't push insulation into the eaves. You need that 50mm airflow gap at the edge of the roof so the timbers stay dry. And don't cover the loft hatch. Fit a separate insulated hatch cover if you want to seal it properly.
What you shouldn't DIY: blown fibre (needs specialist equipment), rigid boards in conversions (building regulations sign-off needed), and anything involving electrics or plumbing in the loft. If there are downlighters in the ceiling below, they need fire-rated loft caps fitted before insulation goes over them. Don't skip that step.
We see this constantly. Someone boards their loft for storage, compresses the insulation underneath, then wonders why the bills haven't dropped. Compressed insulation is bad insulation. If you're boarding, use raised loft legs (brands like LoftZone or StoreFloor) that sit on top of the joists and give you the full 270mm of clearance below the board. Keeps the insulation uncompressed. Keeps the storage usable.
What to Check Before Installing
Fix any roof leaks first. Wet insulation is worse than no insulation.
Don't block the soffit vents. The loft needs to breathe, otherwise condensation builds up on the underside of the roof. Keep a clear channel of at least 50mm at the eaves.
Insulate pipes and cold water tanks separately. An insulated loft gets colder than an uninsulated one because you're stopping warm house air from reaching them. Uninsulated pipes in an insulated loft can freeze in a hard winter.
Check for asbestos. In pre-2000 lofts, some flue pipes, old tank lagging and textured ceiling boards contain asbestos. If anything looks suspect, get a sample tested before you touch it. It's usually fine to insulate around sealed, undamaged asbestos, but don't drill it, cut it, or kick up dust.
Check the access. Once the insulation is down, you still need to be able to get into the loft safely. If the hatch is awkward or the loft floor is a maze, deal with that before the insulation turns it into a bigger problem.
Loft insulation is the fastest win in the whole insulation picture. Cheap, simple, effective. Open the eligibility checker. Two minutes. You'll see exactly which grants cover loft insulation for your home and whether you could get it fully funded.