Professional loft insulation costs £300 to £600 for a typical 3-bed semi in 2026. DIY materials cost £150 to £400. The price depends on your loft size, how much insulation you're adding, and whether you're starting from nothing or topping up existing insulation.
Professional installation costs
| House type | Loft area | Professional cost |
|---|---|---|
| Mid-terrace | 30-35 m² | £300-£450 |
| Semi-detached | 40-50 m² | £400-£600 |
| Detached | 60-80 m² | £800-£1,200 |
This includes materials, labour, and clearing old insulation if needed. Installation takes 3 to 5 hours for most houses.
DIY material costs
If you install it yourself, you only pay for materials. Mineral wool rolls cost £5 to £8 per square metre for 270mm depth.
For a typical 40m² loft (semi-detached house):
- Mineral wool rolls (270mm): £200-£320
- Loft hatch insulation: £20-£30
- Pipe lagging: £15-£25
- Protective gear (mask, gloves, goggles): £20
- Total DIY cost: £255-£395
Installation takes a full day if you've never done it before, half a day if you have. You'll need a dust mask, gloves, goggles, and old clothes. Mineral wool is itchy to handle.
What affects the cost
Loft size
Larger lofts need more material and take longer to insulate. A detached house costs roughly double a mid-terrace.
Starting depth
If you're topping up from 100mm to 270mm, you need less material than starting from bare joists. Topping up costs about 60% of a full install.
Clearing old insulation
If your existing insulation is damp, compressed, or contaminated with debris, it needs removing first. Adds £100 to £200 to the cost for labour and disposal.
Access and clutter
If your loft is full of stored items, the installer will charge more to work around them or you'll need to clear it yourself before they start. Difficult access (small hatch, no boarding) also adds time and cost.
Type of insulation
Mineral wool is cheapest (£5-£8/m²). Sheep's wool costs more (£10-£15/m²) but is easier to handle and performs slightly better. Blown insulation (cellulose or mineral fibre) costs similar to mineral wool once you factor in the specialist equipment and labour.
Hidden costs to watch for
Some installers quote a low price then add extras. Check if the quote includes:
- Loft hatch insulation
- Pipe and tank lagging
- Boarding around the hatch for access
- Clearing old insulation
- Waste disposal
A proper quote should list what's included. If it's just "loft insulation £400", ask what that covers.
Is DIY worth it?
DIY saves £150 to £300 in labour, but you'll spend a day doing it and it's uncomfortable work. Worth it if:
- You're confident working in a loft
- Your loft is clear and easy to access
- You have the time and don't mind the itchiness
Hire a professional if your loft is cluttered, you're not comfortable at height, or you'd rather pay someone to deal with it. The cost difference is small relative to the long-term savings on heating bills.
Getting quotes
Get at least two quotes. Make sure they're for the same spec:
- Same insulation depth (270mm is the current recommendation)
- Same extras included (hatch insulation, pipe lagging)
- Clear on what happens to old insulation
Ask if they're TrustMark registered. TrustMark installers meet government quality standards. Not essential, but it's a safer bet.
Sources
- Energy Saving Trust (2025), "Loft insulation costs and savings", energysavingtrust.org.uk