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How Much Does It Cost To Insulate A House?

With energy prices rising drastically, many UK households are starting to feel their energy bills are spiralling out of control. That’s why more and more families are looking to save money and keep their homes warm by investing in insulation.

Home insulation is a proven way to improve the energy efficiency of your home. Not only that, but insulation cuts heating costs year on year and adds greater value to a property thanks to an improved EPC rating.

In almost all cases, correctly installed home insulation is an investment that pays for itself. But naturally, there will be some upfront expenses to take into consideration. To help you get a clearer picture of what costs home insulation entails, we’re exploring the average costs of the most common home insulation projects around the UK and what you can hope to save on your energy bills.

We’ll also reveal how you can benefit from a professional home insulation audit completely free of charge. This will help you determine which home insulation materials are appropriate for your house, how much your insulation install will cost, and whether you’re eligible to receive government funding to cover part or all of your insulation expenses. Read on to find out more.

Obviously, the exact costs of any insulation project are dependent on a range of factors. These can include:

  • Which room or area of the house requires insulation
  • The quality and amount of insulation materials needs
  • Whether your house already has some insulation
  • Your home’s current EPC rating and energy efficiency
  • Whether any works or repairs need to be completed before the insulation can be installed


As so many variables will determine the final insulation costs, it’s always recommended to consult with a professional who can make recommendations based on the specific requirements of your property.

What are our all-inclusive insulation estimates based on?

For the purposes of this article, we will be considering the average costs for the most common insulation projects within a typical 3-bedroom semi-detached property. Our estimates are based on top of the range sprayfoam insulation. At Smartstone, we only recommend using the highest-quality insulation materials as these are more likely to guarantee a 25-year lifespan, meaning your investment is more than guaranteed to pay for itself in the long-run through significant energy bill savings. High quality sprayfoam is also known for its effective energy saving properties when compared to other insulation materials available on the market.

Furthermore, we are also factoring in installation and other associated costs, such as preparation of the area within the house before its ready for insulation as well as transport and labour. All in all, these all-inclusive estimates will give you a clearer understanding of the costs entailed when considering your next home insulation project

Cavity wall insulation costs

Uninsulated cavity walls could be causing you to lose around a third of your heating in your home. That’s why cavity wall insulation is considered one of the most effective measures to improve your home’s energy efficiency.

Cavity wall insulation uses materials such as spray foam or mineral wool. Small holes are drilled into the outside walls of the house and the insulation material is injecting into the gap between the inner and outer walls until it is filled. The insulation works by trapping air in the material within the cavity. This keeps cold air out and warm air in. While new builds are typically constructed with insulation already inside the walls, many houses built until the 1990s still have uninsulated cavity walls.

Here are the average costs for cavity wall insulation:

Cost per square metre: £15
Typical wall area: 85m2
Total cost: £1,275

Pitched roof insulation costs

Because heat rises, an uninsulated pitched roof can result in 25% of the heat generated in your home to escape. This is a significant amount of heat and energy being wasted, which will cause energy bills to increase even more as your heating struggles to keep the inside of your home warm.

If you’re a homeowner who only wishes to use their roof area as storage space, then cold insulation is ideal. This is when insulation material, such as glasswool or rockwool, is placed over and between the wooden joists on the floor of your loft, creating a barrier between the ceiling of your home’s top floor and the loft.

Here are the average costs for pitched roof insulation:

Cost per square metre: £35
Typical wall area: 80m2
Total cost: £2,800

Room in roof insulation costs

For homeowners looking to convert their loft space into a liveable room, insulation is a must. In order to insulate a roof to create a cosy living space, insulation material must be installed between the joists and rafters within the roof.

Mineral wool, expanded polystyrene, and spray foam are commonly used as room in roof insulation. During the winter months, this will help keep warm air in and the cold air out. Conversely, in the warmer months, insulation will help block hot air from coming into the loft space, ensuring your upper-level room will never get stiflingly hot.

Here are the average costs for room in roof insulation:

Cost per square metre: £50
Typical wall area: 80m2
Total cost: £4,000

Underfloor insulation costs

If you are living in a property with suspended floorboards, then it may be possible to install insulation in the crawlspace between your timber floors and the concrete beneath. This could reduce heat loss by up to 25%.

Typically, there is no need to insulate your upstairs floors as this will stop warm air from downstairs rising to heat your upper-level rooms. One exception to this rule is if rooms are located above an unheated space, such as garage. In these cases, underfloor insulation is recommended to keep cold and draughts from entering any rooms directly above.

Here are the average costs for underfloor insulation:

Cost per square metre: £35
Typical wall area: 125m2
Total cost: £4,375

Additional insulation costs to consider

With nearly every home insulation project, there may be some additional expenses to factor in.

If your home has damp or mould, it will be crucial to eliminate these problems before any insulation materials can be installed. This is because damp can cause rot and other serious damage to your property. This will not only damage your insulation materials, causing them to lose their effectiveness, but it will also be an extremely difficult and costly problem to solve once insulation is installed. That’s why it’s best to solve any damp and condensation issues beforehand, which will inevitably involve some extra costs.

Furthermore, when you’re planning to insulate the floor of your loft, this will reduce the temperature in this area drastically. As such, in the cold winter months, this could freeze any pipes or water tanks in the loft, which will cause great inconvenience and costly damage. That’s why it’s recommended to also invest in insulating any such pipes and amenities as part of your pitched roof insulation.

As with every insulation project, it’s always best to speak to the professionals who will be able to detect any additional works required for you to get the most out of your insulation and save on your energy bills.

How much could you save by insulating your home?

Home insulation is without a doubt the most efficient and effective way to save money on your energy bills.

Recent reports and analysis have shown that energy efficiency measures are already saving the average British household about £1,000 a year in energy bills. Significantly, experts are insisting that even more focus needs to be placed on insulation, which could “halve future bills”. That’s because many electrical appliances, such as gas boilers, are currently as efficient as they can be. However, the big area for improvement is insulation, which will help UK household move towards net zero.

Of course, exact savings will vary depending on a number of factors. However, returning to a typical 3-bedroom semi-detached house, where average energy bills amount to £1,980 a year, homeowners can look forward to the following annual and lifetime savings:

Insulation Measure Cost Annual Savings Lifetime Savings*
Cavity wall £1,275 £693 £17,325
Underfloor insulation £4,375 £495 £12,375
Pitched roof Insulation £2,800 £495 £12,375
Room in roof insulation £4,000 £495 £12,375


When considering recent energy price rises, it’s clear that insulation offers homeowners a tangible solution to help them save on their energy bills in the long run.

Can I get FREE home insulation?

To get the full picture of all costs and savings for any home insulation projects you have in mind, we recommend calling in Smartstone’s independent and certified auditors for a free home heat loss audit.

By inspecting your property, our auditors will be able to determine the best insulation for your requirements, outline all costs and benefits, as well as indicate potential savings you can look forward to.

We can also help you apply for any government schemes which may contribute towards your insulation expenses. And don’t just take our word for it. Working with industry regulators, we’ve helped Britain’s households apply for more than £3,000,000 in government funding.

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