How to buy loft insulation Loft insulation costs and savings

Thermal imaging shows how little heat escapes from the roofs of two houses with loft insulation. Image courtesy of Horton Levi Ltd. Thermal imaging shows how little heat escapes from the roofs of houses with loft insulation

Installing loft insulation could slash your energy bills by up to £240 a year. The payback time (how long loft insulation takes to pay for itself through savings on your energy bills) is also very quick if you didn't have any before.

The thermal image on the right shows two houses which have had loft insulation installed. The dark colour on the roof means hardly any heat is escaping. The house on the right also has cavity wall insulation fitted, whereas the one on the left doesn't. The yellow-red colour means heat is escaping through the walls.

As well as loft insulation prices and savings, we also explain the types of loft insulation - and we reveal the best free and cheap insulation deals.

Loft insulation costs and savings

Professionally installed loft insulation for a typical three-bedroom, semi-detached house with gas central heating costs around £300. It will take around two years to pay for itself through the savings you’ll make on your heating bills.

The recommended thickness for loft insulation is 270mm. The first thing to do is check whether you have any insulation at all in your loft and, if you do, how much. If you already have some insulation in your loft but it falls short of the recommended 270mm, then you could make further savings on your energy bills by topping it up.

In the tables below, which are separated according to whether you're insulating from scratch or just topping up, you can see how much it costs to install loft insulation, how much you'll save per year in money and CO2, and how quickly you'll make your cash back in bill savings. Of course, it's much cheaper to buy the insulation and fit it yourself - by doing that you'd greatly reduce your payback time. Loft insulation typically costs around £20 for a 100mm roll designed to cover 8.3m².

Loft insulation (0-270mm)
Type of propertyInstallation costSavings per yearCO2 savings per year (kg)Payback time
Detached house (four bedrooms)£395£2409901-2 years
Semi-detached house (three bedrooms)£300£1405802 years
Mid-terrace house (three bedrooms)£285£1355502 years
Detached bungalow (two bedrooms)£375£2008201-2 years

Table notes: figures based on a typical gas-heated home. All data obtained from the Energy Saving Trust (EST).

Loft insulation (120-270mm)
Type of propertyInstallation costSavings per yearCO2 savings per year (kg)Payback time
Detached house (four bedrooms)£310£259510-11 years
Semi-detached house (three bedrooms)£250£155514-15 years
Mid-terrace house (three bedrooms)£240£155014-15 years
Detached bungalow (two bedrooms)£295£208010-11 years

Table notes: figures based on a typical gas-heated home. All data obtained from the Energy Saving Trust (EST).

Until the end of 2012, a government-backed scheme called Cert ensured that most people were eligible to receive free or discounted insulation. Though most of these offers have now ended, some suppliers still offer free insulation to householders who fit certain criteria (such as being a member of a vulnerable group or those who receive certain benefits). Check which free offers are available in our guide to free insulation.
A man installing loft insulation

Loft insulation can save you up to £250 a year and pay back in less than two years

Loft or roof insulation?

Lofts are usually cheaper and easier to insulate than roofs. But if your loft is being used as a living space, you would have to insulate the roof. Our guide to roof insulation shows you the options available.

Fitting loft insulation

One reason some people don't insulate their loft is because they want it for storage - the new minimum 270mm required thickness of insulation would go over the joists, making it impossible to lay boards on top. 

But there is a way around this, enabling you to both have 270mm of insulation and use your loft for storage:

  • Insulate between the joists with mineral wool and then lay rigid insulation boards on top, with wooden boarding on top of that. You can buy insulation board pre-bonded to floor boarding to make the job easier.
  • You could also raise the level of the floor so you can fit enough mineral wool beneath the new floor level. 

Either way, make sure you don't squash the mineral wool when you fit the boards on top. If you do, this will reduce its insulation properties. 

Improve your home's energy-efficiency rating

The energy performance certificate (EPC) you get when you buy a home shows an overall energy-efficiency rating for your home from A (the most energy efficient) to G (the worst). It also contains advice on how to cut carbon emissions and fuel bills by making home improvements.

If you're selling a property in England or Wales, you must get an EPC. You'll also need one if you're a landlord looking to market a property for rent - like buyers, prospective tenants can ask to view this before they sign a rental contract.

Fitting insulation is an effective way of raising your home’s energy-efficiency rating. If your home isn't insulated, the EPC will recommend the type and level of insulation required for maximum efficiency.

If you do have loft insulation but it’s deemed to be old, inadequate or inefficient, the EPC may also recommend necessary improvements.

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