Loft Insulation — One of the Simplest Ways to Cut Heat Loss
An uninsulated home loses around a quarter of its heat through the roof. Insulating the loft floor keeps more of that heat in the rooms below.
Every unit of heat that escapes through the roof has to be replaced by your boiler or heat pump. Laying insulation across the loft floor slows that loss, so rooms stay warmer for longer and the heating runs less. The Energy Saving Trust says loft insulation should last around 40 years when installed correctly, so it can pay for itself many times over.
- Yearly saving, empty loft to 270mm
- £140–£360
- Typical professional cost
- £650–£1,200
- Recommended depth of mineral wool
- 270mm
- Heat lost through an uninsulated roof
- ~25%
What Is Loft?
Loft insulation is a layer of material laid between and over the joists of the loft floor to reduce heat loss through the roof. Mineral wool rolls are the most common choice; current guidance recommends at least 270mm of mineral wool, while other materials need different depths. Rooms in the roof and flat roofs need different methods and a professional installer.
How It Works
Survey
The installer checks access, the depth of any existing insulation, ventilation, wiring and any signs of damp.
Preparation
Any damp is fixed first. Pipes and water tanks in the loft are lagged, because the loft space will be colder once the floor is insulated.
Installation
A layer is laid between the joists, then a second layer across them at right angles to reach the recommended depth, keeping eaves ventilation clear.
Finishing Touches
The loft hatch is insulated and draught-stripped. If you need storage, boards are raised above the insulation so it is not squashed.
Is It Right for My Home?
Most homes with an accessible loft can be insulated, and many already have some insulation that can be topped up. Speak to a professional if the loft is damp, is used as a living space, is hard to reach, or if you have a flat roof. The Energy Saving Trust does not recommend spraying foam onto the underside of a roof to fix leaks or damage.
Key Benefits
Lower Heating Bills
Insulating an empty loft to 270mm saves around £140 a year in a mid-terrace house and £360 in a detached house (Energy Saving Trust).
Long Lasting
Correctly installed loft insulation should last around 40 years.
Warmer Rooms
Less heat escapes through the ceiling, so rooms below stay warmer for longer.
Lower Carbon Emissions
Using less heating means lower carbon emissions from your home.
Heat Pump Ready
A well-insulated home is a better starting point if you later switch to low-carbon heating.
Top-Ups Still Help
Topping up from 120mm to 270mm saves less — around £13–£35 a year — but still keeps more heat in.
Ask for a Free Loft Quote
Typical Costs and Savings
Typical figures to help you compare, not a quote for your home. Your costs and savings depend on the property, how you heat it and how you use energy.
| Example | Typical Cost | Typical Saving a Year |
|---|---|---|
| Detached house | £1,100 | £360 |
| Semi-detached house | £750 | £190 |
| Mid-terrace house | £650 | £140 |
| Detached bungalow | £1,200 | £350 |
Energy Saving Trust estimates for insulating a gas-heated home from no loft insulation to 270mm, based on fuel prices as of July 2026. Costs are average unsubsidised professional prices; topping up from 120mm saves much less. Source: Energy Saving Trust — roof and loft insulation. Last reviewed September 2026.
Help With the Cost
Funding depends on where you live, your income and your home, and schemes change. We are not a government body — check the official scheme before relying on it.
Warm Homes: Local Grant (England)
Council-run funding for loft, wall and floor insulation in lower-income households living in homes rated EPC D–G.
Read more on our grants guide →0% VAT until 31 March 2027
Professionally installed insulation in a home is zero-rated for VAT until 31 March 2027.
Read more on our grants guide →Frequently Asked Questions
Your next step
Thinking about Loft Insulation?
It is free to ask and there is no obligation.