Paying a professional to insulate an empty loft to 270mm costs roughly £650 to £1,200 in England, Scotland and Wales, and £950 to £1,700 in Northern Ireland. On the Energy Saving Trust's figures, that pays for itself in three to five years. Topping up a loft that already has about 120mm is a different sum. It costs £500 to £1,000 for a saving of £13 to £35 a year, so pay for that only if it's funded or you're doing it yourself.
Whether you pay anything at all may come down to where you live, because each of the four nations has its own mix of free routes, and the one covering England, Scotland and Wales closes on 31 December 2026.
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What a loft insulation job costs for your house
On loft insulation cost, the Energy Saving Trust publishes typical installed prices and yearly bill savings for four house types. It gives two starting points, a bare loft and one with 120mm already down. There's one set of figures for England, Scotland and Wales, and a separate set for Northern Ireland. We've added the column most quote pages leave out: payback, which is simply the price divided by the yearly saving.
England, Scotland and Wales: what a professional job costs and saves
| House type | Empty loft to 270mm | Saves a year | Pays back in about | Top-up from 120mm | Saves a year | Pays back in about |
|---|---|---|---|---|---|---|
| Detached house | £1,100 | £360 | 3 years | £800 | £35 | 23 years |
| Semi-detached house | £750 | £190 | 4 years | £600 | £17 | 35 years |
| Mid-terrace house | £650 | £140 | 5 years | £500 | £13 | 38 years |
| Detached bungalow | £1,200 | £350 | 3 years | £800 | £35 | 23 years |
Typical installed prices and yearly bill savings are the Energy Saving Trust's. Payback is the price divided by the yearly saving, rounded to the nearest year, with no allowance for energy prices changing.
Northern Ireland's prices are higher on every row, so the Trust publishes them on their own.
Northern Ireland: what a professional job costs and saves
| House type | Empty loft to 270mm | Saves a year | Pays back in about | Top-up from 120mm | Saves a year | Pays back in about |
|---|---|---|---|---|---|---|
| Detached house | £1,500 | £380 | 4 years | £950 | £35 | 27 years |
| Semi-detached house | £1,100 | £230 | 5 years | £700 | £20 | 35 years |
| Mid-terrace house | £950 | £210 | 5 years | £650 | £19 | 34 years |
| Detached bungalow | £1,700 | £370 | 5 years | £1,000 | £35 | 29 years |
Prices and savings are the Energy Saving Trust's Northern Ireland figures, with payback worked out the same way, to the nearest year.
Read across any row and the pattern jumps out. An empty loft pays back in three to five years. A top-up from 120mm takes somewhere between twenty-odd years and nearly forty. That second number deserves a closer look before you sign anything.
Is it worth topping up loft insulation from 120mm?
For most people paying full price, no. The Energy Saving Trust says going from around 120mm to 270mm "could save you" £17 a year in Great Britain and £20 in Northern Ireland. The same Trust expects loft insulation to last around 40 years. Set a paid top-up against those figures and it needs 23 to 38 years to earn its money back, which is most of the insulation's working life.
So we'd do one of three things instead. Do it yourself, get it funded, or fold it into a job that already has you up in the loft.
There's one caution running the other way. The Trust only publishes two starting points, a bare loft and 120mm. If your layer is thinner than that, a top-up saves more than the £17 suggests: the closer you are to bare joists, the closer you get to the empty-loft figures.
What a top-up costs if you do it yourself
DIY is the genuinely cheap loft insulation route. The Energy Saving Trust says you can tackle it if the loft is easy to get into, free of damp and not a flat roof. The method is simple. The first layer goes between the joists, and a second goes at right angles across them.
Say your loft floor is 40 square metres, purely as an illustration. Wickes sells a 170mm top-up roll covering 6.47 square metres, so 40 divided by 6.47 comes to 6.18, which means seven rolls. The roll was on offer at £27 when we checked, about £4.17 a square metre, down from £38. That makes the materials £189 on offer or £266 at full price, plus delivery. Against the Trust's £17 a year, that's about 11 years to pay back at the offer price and about 16 at full price.
That sum already includes VAT. HMRC says the sale of insulation by a retailer "is always standard-rated", while a business fitting it in your home charges 0% until 31 March 2027.
Before you unroll anything, look for wiring. The Trust warns that covering cables with insulation is a fire risk. For recessed lights, check the fitting instructions before placing insulation around or over them.
When paying someone for a top-up does make sense
Four situations change the sum, and in each of them we'd happily pay a professional.
- Someone else is paying. A funded installation makes payback irrelevant, and the free routes differ by nation.
- Your loft has well under 120mm. The thinner the layer, the more a top-up saves, heading towards the empty-loft figures.
- The old layer is spoiled. The Trust says insulation that's very old, damaged by weather or vermin, or compressed is best taken out and replaced.
- You're clearing the loft anyway. If boarding or a new hatch has you up there already, the top-up rides along with work you're paying for regardless.
Check your loft before anyone quotes
Three checks, done with a torch and a tape measure, settle most of what comes next. They tell you which row of the Trust's figures you're in. They tell you whether the job is safe to start at all. And they tell you what a fair quote has to cover, which makes a vague one easy to spot. Do them before any installer visits. It's far easier to judge a price when you already know the answers.
How much loft insulation do you need?
The Energy Saving Trust recommends at least 270mm of mineral wool. Take a tape measure up and check two things: the depth of what's there now, and the gap between the joists, which tells you what width of roll to buy. The Trust says the most common gaps are 400mm and 600mm.
Northern Ireland's Affordable Warmth Scheme goes further. The Housing Executive, which runs it, lists topping lofts up to 300mm among its first-priority measures.
If your tape reads under 100mm, you're far from alone. The English Housing Survey counts over 2.7 million households in England living with less than that. If you've got about 120mm, a 170mm top-up roll takes you past 270mm in a single layer.
Is the loft dry, and are the eaves still open?
Damp comes first. Insulation keeps heat in the rooms below, so the loft itself gets cooler. The Energy Saving Trust warns that this makes condensation more likely and can make existing damp worse. Wet timber, stains or mould need their cause fixing before anything goes down. A leak is a job for a roofer, and damp or mould on the timbers is one for a damp and mould surveyor. It also helps to know how to tell which kind of damp you have before anyone sells you a treatment.
Then look at the edges. Planning Portal's guidance for England says "care should be taken not to block any ventilation at the edges (eaves)", and the Trust says not to cover vents, grilles or airbricks. Condensation after a top-up can start right there, with new insulation pushed into the eaves until outside air can't get in.
Finally, fit an insulated hatch with draught strips round its edges, as the Trust recommends. It keeps cold air out of the rooms below.
What's already lying between the joists?
Look carefully before anything gets moved.
Loose, fluffy material that's blue-grey or whitish may be asbestos. HSE says loose-fill asbestos insulation can turn up in loft spaces, looks "similar to candyfloss", and is "probably the most dangerous asbestos-containing material". Its instruction is plain: "Do not work on this material under any circumstances unless you are an HSE-licensed contractor." If you see it, stop, come down and leave it alone.
Granular beads are likely to be vermiculite. The English Housing Survey puts 100mm of vermiculite at about 67% as effective as the same depth of mineral wool, so a loft full of it is thinner than it looks.
Cables and downlights need keeping clear. Whether insulation can sit over a downlight depends on the fitting itself, and guards keep it off the ones that can't take it. If you're unsure about any of the wiring, ask an electrician. And if there's a cold water tank, the Trust says to insulate its top and sides, never underneath.
Can you still get loft insulation free?
Possibly, but the clock is running. ECO4, the scheme that makes energy suppliers pay towards insulation for eligible households in England, Scotland and Wales, ends on 31 December 2026. The government's response to its own consultation says "there will be no successor obligation after ECO4". The Great British Insulation Scheme has already gone, and GOV.UK says its installations had to be finished by 31 March 2026.
What's left depends on which of the four nations you live in. Each runs its own schemes with its own tests, so a household that qualifies in Cardiff might not qualify in Carlisle. Scheme rules change quickly, so let the scheme's own eligibility check have the final word.
Funded routes by nation
| Nation | Route | Mainly for | Worth knowing |
|---|---|---|---|
| England, Scotland, Wales | ECO4, through energy suppliers or your council | Households on listed benefits, in owned homes rated D to G or privately rented homes rated E to G | Ends 31 December 2026, with no successor |
| England | Warm Homes: Local Grant | Privately owned homes rated D to G, household income usually £36,000 or less | Only where your council has funding |
| Scotland | Warmer Homes Scotland | Passport benefits, or someone aged 75 or over with no working heating | Support worth £10,000 or more |
| Scotland | Home Energy Scotland Grant and Loan | Any homeowner, no benefits needed | Loft grant up to £1,500; written offer before work starts |
| Wales | Nest | Means-tested benefit or low income, home rated E or lower | Free improvements, including insulation |
| Northern Ireland | Affordable Warmth Scheme | Total gross household income under £23,000 | Grants up to £7,500; being replaced |
| Northern Ireland | NISEP | Mostly vulnerable households | 2026/27 schemes open now |
The full conditions, and how to apply, follow nation by nation.
England
ECO4 runs until 31 December 2026. GOV.UK lists the benefits that qualify: Universal Credit, Pension Guarantee Credit, Pension Savings Credit, Income Support, income-based Jobseeker's Allowance, income-related Employment and Support Allowance, Child Benefit and Housing Benefit. If you own your home, it must be rated D to G for energy efficiency. If you rent privately, it must be E to G. GOV.UK suggests asking your council whether it's taking part, or going to an energy supplier directly.
The Warm Homes: Local Grant is England only. It covers privately owned homes rated D to G where household income is usually £36,000 or less, and it only works where your council has funding. When it does, the council arranges and pays for the work. From 2027/28 the government intends to fold it into a single low-income scheme delivered area by area.
Planning a heat pump as well? The Energy Saving Trust says loft insulation helps get a home ready for one, and the heat pump grant comes with its own rules.
Scotland
Scotland has two routes. Warmer Homes Scotland is for households struggling to heat their homes, with support worth £10,000 or more. You get in through a passport benefit such as Adult Disability Payment, Universal Credit or Pension Credit Guarantee, through someone aged 75 or over with no working heating, or with a DS1500 or BASRiS form from a medical professional.
The Home Energy Scotland Grant and Loan is open to any homeowner living in the property as their main home, and you don't need to be on benefits. Loft insulation carries a grant of up to £1,500, plus up to £500 as an interest-free loan. The grant covers up to 75% of the cost. The work must be recommended on your EPC, and you can't start until the offer arrives in writing.
On a £750 loft job, the 75% grant comes to £562.50, well under the £1,500 cap, and the remaining £187.50 could be taken as the interest-free loan. That shows how the percentage and the caps interact. It isn't a promise of any award. The scheme doesn't fund spray foam.
Wales
In Wales the route is Nest, the Welsh Government scheme offering free home energy improvements, insulation among them. You need to own your home or rent it privately, and either get a means-tested benefit or live on a low income. The home must be rated 54 (E) or lower, or 68 (D) or lower if someone in the household has an eligible health condition.
Nest measures income after mortgage or rent. Two of its thresholds give the scale: £23,166 a year for a couple with no children, and £15,521 for a single adult. If you're unsure, ring anyway. Nest's freephone number is 0808 808 2244, and it can also check whether you're entitled to other grants or benefits.
Northern Ireland
ECO4 doesn't cover Northern Ireland, which has two routes of its own. The Affordable Warmth Scheme, run by the Housing Executive, is for owner-occupiers and private tenants with a total gross household income under £23,000. The Housing Executive's own scheme page puts grants at up to £7,500, with loft top-ups to 300mm as a first-priority measure, and no work can start before approval arrives in writing. The Department for Communities has consulted on a Warm Healthy Homes Fund to replace it.
NISEP, the Northern Ireland Sustainable Energy Programme, is paid for by every electricity customer through their bills. Its 2026/27 schemes are live, loft insulation is among the measures, and most of the money goes to vulnerable households. Some schemes ask for a contribution, depending on your income. For both routes, start with the NI Energy Advice service on freephone 0800 111 4455.
What a fair quote should spell out
On this job, the expensive surprise usually hides in one line. A top-up lays new insulation over what's there. A strip-and-replace takes the old layer out first, which is more work, and the sources checked here don't publish a price for it. So make the quote say which one you're getting, and why.
VAT is the easiest line to check. Installed insulation in a home is zero-rated until 31 March 2027, and 5% from 1 April 2027. A quote that adds 20% to the fitted job has got it wrong.
What a fair loft insulation quote should show
- The finished depth in millimetres, and the thickness of each layer going down, so you can check it reaches at least 270mm.
- Whether your existing insulation stays. Laying new over old is normal when the old layer is dry and uncompressed.
- How the eaves will stay ventilated, and that no vents, grilles or airbricks will be covered.
- What happens around the cold water tank and pipes: insulated on top and sides, with nothing underneath the tank.
- How cables and recessed lights will be handled safely, including whether downlights need guards.
- Whether the loft hatch will be insulated and draught-stripped.
- If you want storage, boarding raised above the insulation with a ventilation gap, not boards pressed onto it.
- VAT at 0% on installed insulation until 31 March 2027, and 5% from 1 April 2027.
When someone offers you a free loft check
Some offers to look at your loft are genuine scheme work. Others use the mineral-wool and spray-foam pitches the Trust warns about below.
The Energy Saving Trust has heard from people told their mineral wool had to come out because it "no longer complied with regulations". Its verdict: "Some installers have used this misinformation to try and increase sales." The Trust also rates spraying vapour-impermeable foam onto the underside of an old, poorly maintained roof as "one of the highest risk insulation options there is", while mineral wool at joist level is one of the lowest.
GOV.UK says installers or agents might contact you directly, and if you're unsure an offer is genuine, check with your council or the energy supplier they say they represent. Home Energy Scotland is plainer still: "we never cold call". If the pitch includes a certificate said to help with your EPC, a valuation or equity release, ask which body issues it and check that body yourself. It's worth knowing how to check an installer is registered before anyone reaches your landing.
Signs a loft check is a sales pitch:
- A call or knock you didn't ask for. Check the offer with your council or the energy supplier they claim to represent before anyone goes up the ladder.
- Being told your mineral wool no longer meets regulations and has to come out. Ask for that in writing, then get a second opinion.
- Spray foam on the underside of the roof offered as the fix, especially for a leak. Get the roof repaired first and ask about mineral wool at joist level.
- A price far above the Energy Saving Trust's typical figure for your house type. Get two more quotes before you sign anything.
- A discount that ends today, or a deposit taken on the doorstep. Take the paperwork away and decide tomorrow.
The safest order is the one you control. Measure your depth, find your house type's row in the Trust's figures, and only then ask for prices, from insulation installers near you that you contacted yourself.
Loft insulation questions people ask
How long does loft insulation last?
Around 40 years, if it's installed correctly, according to the Energy Saving Trust. That's why an empty loft is such an easy call: it pays for itself within about five years and keeps working for decades after. Replace it sooner if it's very old, has been damaged by weather or vermin, or has been squashed flat, because compressed insulation keeps less heat in.
Can you put new loft insulation over old?
Yes, as long as the old layer is in good condition. The Energy Saving Trust says you can just add a layer on top, laid at right angles across the joists. Take out anything that's damp, damaged by weather or vermin, or compressed before you start. If someone tells you sound mineral wool no longer complies with regulations, the Trust calls that misinformation used to sell replacements.
Do you need building regulations approval for loft insulation?
The work has to meet building regulations standards, but planning permission isn't normally needed. For England, Planning Portal says loft insulation must meet the minimum energy efficiency values in the Approved Documents, and a renovation renewing more than 25 per cent of the roof must meet the full standard. Keep the eaves ventilation clear, and ask your planning authority first if the building is listed or in a conservation area. Welsh policy may differ. In Northern Ireland, the Energy Saving Trust says building regulations require adequate ventilation, so check with building control.
Can you board over loft insulation?
Yes, but don't lay boards straight onto it. The Energy Saving Trust's method is to raise the floor slightly, add a second layer of insulation across the joists, then fit the boards on top with a small gap for ventilation. That gap stops condensation. Never squash mineral wool to make the boards fit, because compressed insulation stops doing its job.
Is loft insulation VAT free?
Yes, when a business installs it in your home, until 31 March 2027. From 1 April 2027 the rate becomes 5%. Rolls you buy from a shop to fit yourself are different. HMRC's VAT Notice 708/6 says the sale of energy-saving materials by a retailer is always standard-rated, so the shelf price carries the full 20%. If an installer's quote adds 20% to a fitted job, query it.
Can you get free loft insulation on Universal Credit or PIP?
Universal Credit can qualify you for ECO4 until 31 December 2026. It's on GOV.UK's benefits list, as long as your home meets the energy-rating conditions. PIP isn't on that list. In Scotland, Adult Disability Payment is a passport benefit for Warmer Homes Scotland. In Wales, Nest can take a D-rated home where someone has an eligible health condition. Northern Ireland's Affordable Warmth Scheme goes on income. GOV.UK also suggests asking your council whether it's taking part in ECO4.
Should you insulate the roof slope instead of the loft floor?
Not if the loft floor is an option. The Energy Saving Trust says insulating at rafter level is much more expensive than standard loft insulation and much less energy-efficient, partly because you end up heating the loft air too. The installer also has to insulate any gable walls, party walls and chimneys in the loft. It isn't a DIY job. If you use your loft as a living space, the Trust says to speak to a professional installer.