Loft insulation costs between £300 and £1,500 in the UK, depending on whether you do it yourself or hire a professional installer. DIY mineral wool rolls cost from £300 for a 3-bed semi, while professional installation ranges from £400-£1,500. With energy savings of £315-£590 per year for a detached home, loft insulation is the single best-value energy upgrade available.
We have compared professional installer rates, DIY material costs, and energy savings data to produce an accurate loft insulation cost guide for 2026. All prices are based on current UK builder and installer rates for the recommended 270mm depth. We also cover grants that can make loft insulation free for qualifying households.
- DIY loft insulation costs from £300 for a 3-bed semi - mineral wool rolls from a builders’ merchant are the cheapest option, and the job takes a competent DIYer 4-6 hours
- Professional installation costs £400-£1,500 depending on home size - includes clearing the loft, fitting 270mm insulation, and boarding if requested, typically completed in one day
- Topping up from 100mm to 270mm saves £130-£200 per year - many homes installed in the 1980s-2000s only have 100mm depth, well below the current 270mm recommendation
- Free loft insulation is available through ECO4 and GBIS schemes - eligible households on qualifying benefits or in EPC band D-G properties pay nothing for professional installation
- Spray foam loft insulation costs £1,200-£3,500 but carries mortgage risks - some lenders refuse properties with spray foam, so check lender requirements before committing
How Much Does Loft Insulation Cost?
Loft insulation costs depend on the installation method, your loft size, and whether you are starting from scratch or topping up existing insulation. A new full installation costs more than a simple top-up, but both deliver strong returns through lower heating bills.
| Installation Type | DIY Cost | Professional Cost | Annual Saving |
|---|---|---|---|
| Full install (0 to 270mm) | £300-£500 | £400-£1,500 | £315-£590 |
| Top-up (100mm to 270mm) | £150-£300 | £250-£600 | £130-£200 |
| Blown-in insulation | N/A | £500-£1,200 | £315-£590 |
| Spray foam (open-cell) | N/A | £1,200-£3,500 | £315-£590 |
Energy savings figures are from the Energy Saving Trust and assume gas central heating in a detached home going from no insulation to full 270mm coverage. Smaller properties and top-up installations will see proportionally lower savings, but the lower cost also means payback is still fast.
Cost by House Type
Your loft area directly determines how much insulation material you need and how long installation takes. Larger homes cost more but also save more on heating bills, keeping the payback period broadly similar across property types.
| House Type | Approx. Loft Area | Professional Cost | Annual Saving | Payback |
|---|---|---|---|---|
| Mid-terrace | 30-40 m2 | £400-£700 | £150-£240 | 2-3 years |
| Semi-detached | 40-55 m2 | £500-£900 | £225-£380 | 2-3 years |
| Detached | 55-80 m2 | £700-£1,500 | £315-£590 | 2-3 years |
| Bungalow | 50-70 m2 | £600-£1,200 | £280-£500 | 2-3 years |
Bungalows have proportionally larger loft areas relative to their floor space, which means loft insulation has an even bigger impact on energy bills. If your bungalow has no loft insulation, this should be the first upgrade you make.
Roll vs Blown-In Insulation
Roll insulation (mineral wool batts laid between and over joists) is the standard approach for accessible lofts. Blown-in insulation uses a machine to blow loose mineral wool or cellulose fibre into the loft space, covering hard-to-reach areas that rolls cannot easily reach.
For most lofts with standard joist spacing and reasonable access, rolls are cheaper and perfectly effective. Blown-in is the better choice if your loft has irregular joist spacing, lots of pipes and cables to work around, or restricted headroom that makes laying rolls difficult.
Both methods achieve the same thermal performance when installed to 270mm depth. The main difference is cost – blown-in typically costs £500-£1,200 compared to £400-£900 for rolls in the same property. Blown-in must be professionally installed, while rolls are straightforward for a competent DIYer.
Can I Do Loft Insulation Myself?
Loft insulation is one of the few insulation types that a competent DIYer can tackle successfully. Laying mineral wool rolls between and over joists requires no specialist tools or skills, just care, patience, and proper protective equipment.
Wear a dust mask (FFP3 rated), goggles, gloves, and long sleeves when handling mineral wool. The fibres cause skin irritation and should not be inhaled. Use a board across the joists to kneel on and never step between them – the ceiling below will not support your weight.
The basic process is: clear the loft of stored items, lay the first layer of insulation between the joists (100mm), then lay the second layer across the joists at right angles (170mm) to eliminate cold bridges. Leave gaps around recessed light fittings (fire risk) and the eaves (ventilation). The total depth should reach 270mm.
DIY loft insulation costs £300-£500 for materials. Budget mineral wool rolls (100mm x 8m) cost around £6-£10 per roll from builders’ merchants, and you will need roughly 10-15 rolls for a 3-bed semi. The job takes a competent DIYer 4-6 hours.
However, DIY is not always the best choice. If you qualify for a government insulation grant, professional installation is free. Even if you do not qualify, the price difference between DIY and professional is often only £100-£400, and professionals complete the job faster with a guarantee.
Recommended Insulation Depth
The current recommended loft insulation depth is 270mm (approximately 10.5 inches), set by Building Regulations Part L. Many older homes have significantly less than this, often just 25mm or 100mm installed when the house was built.
If your existing insulation is below 270mm, topping up is one of the cheapest energy upgrades you can make. Adding 170mm on top of existing 100mm insulation costs £150-£300 for DIY or £250-£600 for professional installation, and can save £130-£200 per year on heating bills.
Check your current depth by measuring the insulation between your loft joists. If it is below the top of the joists (typically 100mm deep), you have significant scope for improvement. Even homes with insulation up to joist level benefit from a cross-layer on top to eliminate cold bridges at the timber joists.
Spray Foam Loft Insulation
Spray foam loft insulation costs £1,200-£3,500 and involves applying open-cell polyurethane foam to the underside of the roof tiles. It creates an airtight seal and effectively turns the loft into a warm space, eliminating draughts and condensation.
The main benefit over mineral wool is that spray foam fills every gap and crack, achieving a consistently airtight finish. It also does not settle or degrade over time. Some homeowners prefer spray foam because it allows the loft to be used as a warm storage space or room-in-roof conversion.
Some mortgage lenders will not lend on properties with spray foam in the loft. The concern is that spray foam prevents inspection of roof timbers for structural issues. Before committing, check with your current lender and consider future saleability. BBA-certified products installed by approved contractors reduce this risk.
Loft Insulation Grants
Free loft insulation is available through government schemes for eligible households. The two main programmes are ECO4 (Energy Company Obligation) and GBIS (Great British Insulation Scheme), both of which fund loft insulation as a priority measure.
ECO4 covers households receiving qualifying benefits including Universal Credit, Pension Credit, and Child Tax Credit. GBIS extends eligibility to owner-occupiers in council tax bands A-D with properties rated EPC band D or below, regardless of income. Both schemes fund professional installation to 270mm depth at no cost to the homeowner.
Even if you do not qualify for free insulation, topping up your loft is so affordable (£150-£300 for DIY) that it rarely makes sense to delay. The annual savings typically exceed the cost within the first year or two. For full grant details, see our insulation grants guide, our ECO4 guide, and our GBIS guide.
For a comparison of all insulation types and costs, visit our home insulation cost hub. If your home has solid walls, external wall insulation or cavity wall insulation may also be worth considering alongside loft insulation.
