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7 May 2021

Loft insulation costs and savings

Weigh up the costs and savings of installing loft insulation
Installing loft insulation 450367
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WhichEditorial team

Loft insulation could reduce your energy bills by up to £215 per year, depending on your home.

We’ve found out how much it costs to install and how long loft insulation will take to pay for itself. 

The payback time is short if you started out with no loft insulation. But we've found that even homes with existing loft insulation can save money by increasing the amount.

Keep reading for loft insulation prices and savings, or see different Types of loft insulation or find out if you could get free loft insulation.

How much does loft insulation cost?

We've worked with the Royal Institution of Chartered Surveyors* (RICS), which publishes average building work and repair costs, to bring you the average cost for loft insulation. 

It's split into the average costs for a terraced, semi-detached and detached house, fitted by a professional. Bear in mind that costs will vary, depending on where you live in the country. 

Only logged-in Which? members can the costs in the table below. If you're not a member, join Which? to get instant access.

Loft insulation costs

House type Price from Price to
Terraced
Semi-detached
Detached
Table notes: Glass mineral wool insulation quilt laid over and between the joists, 270mm thick.  Data copyright RICS 2020, reproduced with permission. Data is current as of October 2020.  

Of course, it’s cheaper to buy the insulation and fit it yourself. Loft insulation typically costs around £20 for a 100mm-thick roll, designed to cover 8.3m².

Some energy suppliers still offer free insulation to some households who fit certain criteria (such as being in a vulnerable situation or receiving certain benefits). 

Find out if you could get Free loft insulation from energy suppliers.

Loft insulation savings

Professionally installed loft insulation will typically take a couple of years to pay for itself through the savings you’ll make on your heating bills if you go from no insulation to the recommended amount.

The recommended thickness for loft insulation is 270mm. 

First, check whether you have any insulation at all in your loft and, if you do, how much. 

If you already have some loft insulation but less than the recommended 270mm, then you could save more on your energy bills by topping it up.

The charts below show how much loft insulation can save you each year in money and CO2. We've split the savings by whether you’re insulating from scratch or topping up.  

Log in or join Which? to see how quickly loft insulation will likely pay for itself through savings on your energy bills.

Loft or roof insulation?

Lofts are usually cheaper and easier to insulate than roofs. But if your loft has been converted into living space, you'll have to insulate the roof itself. 

See the types of Roof insulation.

Fitting loft insulation

One reason some people don’t insulate their loft is because they want to use it for storage. The required 270mm of insulation material over the joists would make it impossible to lay boards on top. 

But there is a way around this:

  • Insulate between the joists with mineral wool, lay rigid insulation boards on top and wooden floor boarding on top of that. You can buy insulation board that's been pre-bonded to floor boarding to make the job easier.
  • Alternatively, 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 its overall energy-efficiency rating. This ranges from A (the most energy-efficient) to G (the least). It also gives advice on how to cut your carbon emissions and fuel bills.

Switching gas and electricity supplier is another quick way to cut your energy bills.

Description:

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 marketing a property for rent. Like buyers, prospective tenants can ask to see it before they sign a rental contract.

Insulation is a good way of improving your home’s EPC. If your home isn’t insulated, the EPC will recommend the type and amount 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 improvements.

RICS cost calculations

*To arrive at the average prices above, RICS uses cost data from its Building Cost Information Service (BCIS) database, where costs are collated from a variety of sources and analysed. 

Materials costs are based on the best trade prices from a range of suppliers across the UK, which are then benchmarked to reveal the best national average. Labour rates are based on the current Building and Allied Trades Joint Industrial Council wage agreement. Data copyright RICS 2020, reproduced with permission. Data is current as of October 2020.