Loft Insulation Costs UK 2025
Complete Guide to Types, Prices, and Savings
Loft insulation is the single best value home energy improvement you can make. Around 25% of heat in an uninsulated home escapes through the roof. Proper insulation pays for itself in 2 to 3 years through lower heating bills.
This guide covers all loft insulation types from cheap mineral wool to premium spray foam, with realistic costs, pros and cons, and guidance on which option suits your situation.
Best Value Retrofit Measure
Loft insulation consistently ranks as the highest return on investment for home energy improvements. Government data shows average savings of £250 to £350 per year for previously uninsulated homes, with installation costs often recouped within 2 to 3 years.
Loft Insulation Types Compared
Each insulation type has different costs, performance, and suitability.
Costs by Loft Size
Typical costs for different loft sizes and insulation methods.
| Loft Size | Mineral Wool DIY | Mineral Wool Pro | Blown Insulation | Spray Foam |
|---|---|---|---|---|
| Small (30m²) | £150 to £250 | £300 to £450 | £500 to £700 | £1,000 to £1,500 |
| Medium (50m²) | £250 to £400 | £400 to £600 | £700 to £1,000 | £1,500 to £2,500 |
| Large (80m²) | £400 to £600 | £600 to £900 | £1,000 to £1,500 | £2,500 to £4,000 |
| Very Large (100m²+) | £500 to £800 | £800 to £1,200 | £1,300 to £2,000 | £3,500 to £5,000+ |
What Depth Do You Need?
Check your current insulation depth and see what action to take.
| Current Depth | Recommended Action | Estimated Cost | Savings Potential |
|---|---|---|---|
| None (0mm) | Install 300mm new | £400 to £800 | £250 to £350/year |
| Under 100mm | Top up to 300mm | £300 to £500 | £150 to £250/year |
| 100mm to 200mm | Top up to 300mm | £200 to £350 | £100 to £150/year |
| 270mm+ | Already adequate | £0 | Minimal improvement |
How to Check Your Depth
Go into your loft with a torch and ruler. Measure from the top of the joists to the top of the insulation. If insulation is level with joists (typically 100mm), you will benefit significantly from topping up to 300mm.
Available Grants
You may be eligible for free or subsidised loft insulation.
Great British Insulation Scheme
Eligibility: Council tax bands A to D, EPC D or below
Most accessible scheme. Apply through energy suppliers.
ECO4
Eligibility: Low income, certain benefits
Means tested. Can cover full installation.
Local Authority Grants
Eligibility: Check with local council
Some councils offer additional top up funding.
DIY Installation Tips
Mask, goggles, gloves, long sleeves. Mineral wool is itchy.
Never step between joists. Use boards to spread weight.
Leave gaps at edges for airflow to prevent condensation.
Often forgotten but significant heat loss point.
Insulate any water pipes and tanks while you are up there.
Use LED work lights. Good visibility is essential for safety.
Key Takeaways
Calculate Your Insulation Costs
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