How much does loft insulation cost?

Loft insulation for a typical 3-bedroom semi-detached house costs around £300–£600 if you're topping up from 100mm to 270mm, or £500–£1,000 for a full installation from scratch. DIY mineral wool insulation rolls cost £5–£10 per square metre from B&Q or Wickes. Professional installation is relatively inexpensive because mineral wool loft insulation is one of the simplest and most cost-effective energy efficiency improvements. Many households can get it fitted for free or at a discount through government grants.

How much can loft insulation save on energy bills?

According to the Energy Saving Trust, insulating your loft from scratch (0mm to 270mm) in a semi-detached house could save around £355 per year. Topping up from 120mm to 270mm saves around £35 per year. Detached houses save more (up to £590/year from scratch) and mid-terrace houses save less (around £185/year). The payback period for a full installation is typically 1–3 years, making it one of the best investments in energy efficiency.

Can I get free loft insulation?

Yes — loft insulation is covered by several government and energy company schemes. The ECO4 scheme (delivered by energy companies) provides free or subsidised insulation for low-income and vulnerable households. The Great British Insulation Scheme targets less energy-efficient homes in lower council tax bands. In Scotland, Home Energy Scotland offers grants. In Wales, the Nest scheme may help. Contact your energy supplier, local council, or the relevant scheme to check eligibility.

How thick should loft insulation be?

The recommended minimum thickness for mineral wool loft insulation is 270mm (about 10.5 inches). This is usually achieved with 2 layers: one layer (usually 100mm) between the joists and a second layer (170mm) laid on top at right angles, covering the joists. Building Regulations for new builds require even greater thermal performance, but 270mm is the standard recommendation for existing homes. Going thicker (up to 300-400mm) provides marginally better insulation.

Loft Insulation Costs UK 2026 — Prices, Savings & Grants | PocketWise

Loft insulation is one of the cheapest and most effective ways to cut energy bills. Here’s what it costs and how much you’ll save.

At a Glance

Feature	Detail
Recommended thickness	270mm (mineral wool)
Average cost	£300–£1,000 (professional installation)
Average saving	£185–£590/year (depending on house type)
Payback period	1–3 years
Free scheme available?	Yes — ECO4, Great British Insulation Scheme, and others
DIY possible?	Yes for accessible lofts — mineral wool rolls
Lifespan	40+ years
EPC improvement	Can improve by 1–2 bands

Costs by Property Type

Property type	Loft area (approx)	Full installation (0 to 270mm)	Top-up (120mm to 270mm)
Mid-terrace	40 sqm	£300–£500	£200–£350
Semi-detached	50 sqm	£400–£600	£250–£400
Detached	70 sqm	£500–£1,000	£350–£600
Bungalow	60–80 sqm	£450–£900	£300–£500

DIY Costs

Material	Cost per sqm	Cost for 50 sqm (semi)
Mineral wool rolls (100mm)	£4–£7	£200–£350
Mineral wool rolls (170mm)	£6–£10	£300–£500
Total (two layers to 270mm)	£10–£17/sqm	£500–£850

Note: DIY is significantly cheaper but requires care — wear protective clothing (mask, goggles, gloves, long sleeves) as mineral wool fibres irritate the skin, eyes, and lungs.

Energy Savings

Property type	Annual saving (0mm → 270mm)	Annual saving (120mm → 270mm)
Detached	~£590	~£55
Semi-detached	~£355	~£35
Mid-terrace	~£185	~£20
Bungalow	~£400	~£40

Source: Energy Saving Trust estimates (based on current energy prices)

Payback Period

Scenario	Cost	Annual saving	Payback
Full install, semi (professional)	£500	£355	~1.4 years
Full install, detached (professional)	£750	£590	~1.3 years
Top-up, semi (professional)	£300	£35	~8.6 years
Full install, semi (DIY)	£700	£355	~2 years

Full installation from scratch offers an exceptional return. Top-ups from existing insulation offer smaller but still worthwhile savings.

Types of Loft Insulation

Type	Best for	Cost/sqm	Notes
Mineral wool rolls (glass/rock wool)	Accessible lofts with joists	£5–£10	Most common, DIY-friendly
Loose-fill (cellulose, mineral)	Awkward spaces, blown in	£8–£15	Professional installation
Spray foam	Under rafts for rooms-in-roof	£20–£50	Controversial — can affect mortgage ability
Rigid board insulation	Between and over rafters	£15–£30	Good for room-in-roof conversions
Sheep’s wool	Eco-friendly option	£10–£20	Natural, good insulation, no irritants
Multi-foil insulation	Thin profile where space is limited	£8–£15	Less effective per thickness than other options

Warning About Spray Foam

Concern	Detail
Mortgage problems	Many lenders won’t lend on properties with spray foam insulation
Survey issues	Surveyors can’t inspect timbers behind spray foam
Difficult to remove	Expensive to rectify if it causes problems
May not comply with Building Regs	Some types don’t meet regulations
Recommendation	Avoid unless you’ve had independent specialist advice — mineral wool is safer and cheaper

Available Grants

Scheme	Who qualifies	What’s covered
ECO4	Low-income households, certain benefits	Free loft insulation
Great British Insulation Scheme	Council tax bands A–D (England), or bands A–E with benefits	Free or subsidised insulation
Home Energy Scotland	Scotland residents	Grants up to £7,500 for insulation and other measures
Nest (Wales)	Wales residents on low income/benefits	Free home energy improvements
Local council schemes	Varies	Check with your local authority
Energy company obligation	Via your energy supplier	Free or subsidised insulation

How to Apply

Step	Action
1	Check your eligibility on the Simple Energy Advice website (England) or Home Energy Scotland / Nest
2	Contact your energy supplier to ask about ECO4 eligibility
3	Contact your local council for local schemes
4	If eligible, an installer will survey your home and arrange fitting

DIY vs Professional

Factor	DIY	Professional
Cost	£500–£850	£300–£1,000
Time	Half a day to a full day	Half a day
Skill needed	Basic (lay rolls between and over joists)	None — they do everything
Safety	Must wear protective gear (mask, goggles, gloves)	They handle it
Guarantee	None	Usually 25+ years
Best for	Accessible lofts, confident DIYers	Everyone else, especially grant-funded

Things to Check Before Insulating

Check	Why
Roof leaks	Fix any leaks first — wet insulation is useless
Ventilation	Don’t block eaves ventilation — causes condensation
Electrical cables	Lay on top of insulation, not underneath
Pipes and water tanks	Insulate separately — loft insulation keeps heat downstairs, making the loft colder
Loft hatch	Insulate and draught-proof the hatch too
Down-lighters	Fire risk — use loft caps over recessed lights if insulating over them
Damp	Check for condensation issues — improve ventilation if needed

Loft Insulation Costs UK 2026 — Prices, Savings & Grants