Loft Insulation Costs: How Much Does it Cost to Insulate a Loft?

How much does loft insulation cost in the UK? Upgrading loft insulation is one of the most cost-effective ways to reduce heating bills and improve your home’s energy performance. Find out what you’ll pay with our in-depth guide to loft insulation prices and options
Chris Bates, Editor of Build It magazine
by Chris Batesmith
27th March 2024

Understanding how much it costs to insulate a loft and why this is a key investment is essential when undertaking a renovation or self build project. Insulating your loft is one of the most effective ways to reduce your energy bills. We all know heat rises, so it’s no surprise that poorly-insulated attics are among the prime culprits for unwanted heat loss.

If your home has a pitched roof and a flat ceiling on the storey below, then it should be straightforward and cost-effective to add more insulation to your loft. In fact, it should probably be the first place you look if you want to upgrade your home’s energy performance.

Here, I’m taking a look at how much it costs to insulate a loft in the UK, alongside exploring the different loft insulation options and their benefits.

What Type of Insulation Should I Use in My Loft?

There are three main types of loft insulation. These are blanket, loose fill and blown. Each approach has its own pros and cons, plus there’s a choice of materials within the different categories.

Blanket Insulation Pros & Cons

Also known as quilt insulation, this is the go-to choice for easily accessible lofts. It’s sold in easy-install rolls, suitable for either DIY or professional fitting, and comes in standardised widths to snugly fit standard loft joist spacings.

So, you simply roll the insulation out between the joists and cut to length. Depending on the height of the joists and your performance goals, you might then add a perpendicular layer on top to achieve the total insulation depth you require.

Sheeps wool insulation, such as Thermafleece, is more expensive than mineral wool – but offers a sustainable, breathable option

Mineral wool is the most common type of blanket insulation for lofts. It’s available as either glass wool (from the likes of Isover and Knauf) or stone-based fibres (such as Rockwool).

For a natural alternative, consider sheep’s wool insulation (such as Thermafleece). This is about four times the price of glass mineral wool, but offers great sustainability benefits and is better suited to older houses due to its breathability and moisture control properties.

Loose Fill Insulation Pros & Cons

If you’re dealing with uneven or awkwardly-spaced joists, loose fill might be a better and quicker option than manually cutting blanket insulation. It’s a bit more expensive per m² but has some unique benefits. It can be spread across a whole loft or used purely for smaller areas that would otherwise be hard to treat. Loose fill insulation is also popular for topping up existing loft insulation.

Manufactured by the likes of Thermafloc and Soprema, loose fill cellulose insulation (basically recycled newspaper) offers good performance in tandem with impressive sustainability credentials. Alternatives include mineral wool (such as Rockwool’s loft insulation granulate), Steico’s wood fibre insulation and Dupre’s Micafil vermiculate. With the exception of vermiculate, all of these can also be used as blown insulation.

Learn More: Home Insulation: Best Ways to Reduce Heat Loss & Stay Warm

Loose fill cellulose is eco-friendly and ideal for hard-to-reach patches or topping up existing loft insulation. Photo: ISTOCK.COM/MIRONMAX STUDIO

Check the manufacturer’s guidelines for coverage: as a rule, you’ll need around 100L per m² of loft floor to reach a 100mm depth of insulation. You or your installer may need to do some prep work to seal any gaps and protect vents before the loose fill insulation is fitted. It’s best to switch to blanket insulation to treat the loft hatch.

Blown Insulation Pros & Cons

If your loft is particularly difficult to access, it may not be possible to effectively fit either blanket or loose fill insulation by hand. That’s where blown insulation comes in: a professional installer will use specialist equipment to spray the insulation into the loft. This will be a loose-fill or spray-applied material, such as mineral wool, cellulose or a foam-based insulation. The most appropriate choice will depend on the age and characteristics of your home.

Blown insulation is more expensive to install than other types of loft insulation, but may be the best option for hard-to-access spaces with complex roof structures. Photo: ISTOCK.COM/BANKSPHOTOS

One of the downsides of blown insulation is that it’s designed to get into the nooks and crannies – which means there’s an increased risk of blocking much-needed ventilation within the loft space. A good installer will prep the loft to ensure soffit vents etc have sufficient airflow.

Blown insulation also significantly more expensive than blanket or loose-fill, but may be the only option for some roof voids. Switch to blanket insulation to treat the loft hatch.

Inspiring Real-Life Projects: Eco Homes: 36 Sustainable Self Builds to Inspire Your Eco House

EXPERT VIEW How to maximise attic storage without compromising loft insulation

Gareth Storey from Loft Leg shares how to maximise space inside your attic without impacting your loft insulation’s performance and efficiency.

Loft spaces offer valuable opportunities for homeowners seeking additional storage. However, it’s important to not squash your insulation as it’ll lose its effectiveness, leading to higher energy bills and a chilly home.

Loft insulation, typically composed of fiberglass or mineral wool, functions by trapping air. This air creates a thermal barrier, stopping heat transfer between your living space and the outside environment. However, the insulating effectiveness of these materials is directly tied to their thickness or depth.

Compressing insulation by placing heavy objects or installing loft boards directly on top significantly reduces the air pockets and diminishes its properties. Studies indicate that compressing 270mm of insulation down to joist level can lead to a reduction in performance by over 50%, meaning higher energy bills and wasted insulation.

The key to maximising loft storage and preserving insulation efficiency lies in creating a raised platform above the insulation. Purpose-built support systems such as Loft Leg and Loft Leg XL offer an easy and inexpensive DIY solution.

These products function as stilts that elevate the loft boards above the insulation layer. This approach allows homeowners to create a sturdy and walkable storage platform without compromising the thermal performance of their loft insulation.

Gareth Storey is the co-founder and technical director at Loft Leg Ltd.

How Much Loft Insulation Do I Need?

Look around online and you’ll typically see recommendations for loft insulation to be at least 250mm-270mm thick. In new build homes, it’s now quite common to see 300mm-400mm of loft insulation. But the optimum depth for in an existing house project depends on a range of factors.

Thermal performance varies according to the type of insulation you’re using, for instance. Here’s a rough guide to the total depth you’d need to achieve similar results with different materials (bearing in mind the thicknesses they’re commonly sold in):

  • Glass wool blanket insulation 270mm
  • Stone wool blanket insulation 250mm
  • Sheep’s wool blanket insulation 240mm
  • Cellulose loose fill insulation 220mm

Before going ahead, investigate the depth and condition of any existing insulation (60mm-120mm is quite common). If it’s been compressed or become moisture-logged, this will impede performance. So, it might be best to strip it out and start again. If it’s in good condition, however, you could save £100s by simply topping it up to the desired level.

It’s worth noting that you can mix-and-match some materials. For instance, existing mineral wool blanket insulation could be made up with an alternative such as sheep’s wool blankets or with loose fill insulation (which is also excellent for harder-to-reach areas).

Loft Leg

It’s important to avoid compressing your loft insulation as this will impact its performance. Loft Legs are an easy DIY solution, allowing you to install full-height uncompressed mineral wool insulation and board your loft for storage

You might also be limited by the height of the joists. In older homes, these may be as deep as 200m, but in newer houses they’re likely to around 100-150mm. There are two options if you want to install a greater depth of insulation. The first is to simply lay your chosen loft insulation over the top of the joists as well. However, you won’t then be able to use the attic for storage, as compressing the insulation would reduce its performance.

Alternatively, you can raise the height of the joists so you can incorporate more insulation while still using the loft for storage. Loft legs are a great option for this, enabling you to easily board out afterwards.

Loft Insulation Prices: What Does it Cost to Install Loft Insulation in the UK?

This will depend on the material you’re using, how much of it you need to reach the desired thermal performance and who’s doing the work (pro or DIY). The benchmark costs below are based on professional installation and assume you’re going from zero insulation up to 270mm (or the equivalent for different materials).

House typeAssumed loft sizeMineral wool blanket (270mm fibreglass)Sheep’s wool blanket (250mm)Loose fill insulation (220mm cellulose)

We’ve compiled these figures by researching materials prices across a wide range of suppliers. They included an allowance for treating the loft hatch, but don’t account for extras such as increasing joist height or moving electrical cables.

Labour rates for insulating a loft are currently around £200-£300 per day (depending on where you are in the country). A straightforward loft space could be insulated in just a few hours, while larger jobs might require a day. So, fitting loft insulation DIY could save you a few hundred pounds. However, DIY installation is likely to take you longer and may not be feasible on more complex projects.

Installing blown insulation is significantly more expensive due to the need for specialist labour and equipment. Expect to pay at least £55 per m² for blown-in loft insulation (including installation).

Our Guide to DIYing Your Loft Insulation: How to Insulate Your Loft

How Much Money Can I Save by Insulating My Loft?

According to the Energy Saving Trust (EST), upgrading a totally uninsulated loft in a detached house with a 270mm thickness of new mineral wool insulation could save you as much as £415 per annum (based on fuel prices in October 2023).

The EST assumes a cost of around £1,200 for professionally-installed loft insulation in a detached home. That seems a little steep in comparison to other price databases, but still means you can expect payback in under three years.

In practice, most existing homes already have at least some loft insulation already. There’s a law of diminishing returns when it comes to topping this up, so the savings are likely to be much smaller.

“A little insulation goes a long way, whereas it takes a lot more of it to do just a little more work,” says Nigel Griffiths, Build It’s sustainability expert. “It might not be worth topping up loft insulation if you already have, say, 150mm of mineral wool in place.”

Rockwool offers a range of stone wool loft insulation rolls delivering both thermal and acoustic performance benefits

Indeed, the Energy Saving Trust suggests savings of £40 per year when taking a detached house from 120mm to 270mm of loft insulation, against an installed cost of £930 – meaning it would take over 20 years to recoup your investment.

So, the trick is finding the right balance between installed cost and potential savings. Adding an extra 75mm-100mm of loft insulation, for instance, could do most of the work at less than half the cost of going all the way to 270mm.

Are There Currently Any Free Loft Insulation Grants in the UK?

There are currently two schemes operating across England, Scotland and Wales that offer free or reduced-cost loft insulation: the Energy Company Obligation (ECO) and the new Great British Insulation scheme. In both cases, you can apply through your existing energy supplier.

The Energy Company Obligation is designed for low-income households and you can apply for multiple energy efficiency improvements, including loft insulation. There are various eligibility criteria to meet for ECO, such as total household income, whether anyone in the house qualifies for benefits etc. The property must also have an EPC (energy performance certificate) rating of D or below if you own the house, or an EPC E or below if you’re renting.

Qualifying criteria are similar for The Great British Insulation Scheme, but the house must also be in council tax band A to D in England, or A to E in Scotland and Wales. As the name suggests, this scheme is focussed on insulation measures.

Unlike ECO, you can only apply for a single upgrade under the Great British Insulation Scheme – so you can’t get support for both cavity wall and loft insulation, for instance. In some circumstances, you may be expected to pay a proportion of the costs. The government has produced an online eligibility checker for the Great British Insulation Scheme.

Funding is also available via more localised schemes, including:

  • The Home Upgrade Grant is available to households in England that do not use a gas boiler as their main heating system. Primarily aimed at low-income households.
  • Warmer Homes Scotland is a programme for those struggling with energy bills offering funding and support for a range of measures, including loft insulation, draughtproofing, central heating upgrades and renewables.
  • Nest in Wales is a similar warm homes scheme, offering a package of free home energy efficiency improvements to eligible households, such as new boilers, central heating, insulation, solar panels and heat pumps.
  • The Northern Ireland Sustainable Energy Programme supports a range of eco improvements, including loft insulation. There’s also an Affordable Warmth Scheme aimed at low-income households.

More Useful Advice: Insulating a Self Build Home: How Sustainable are the Options?

Do I Have to Pay VAT on Loft Insulation?

Under energy saving materials rules introduced in 2022, if you engage a professional to supply and install insulation in your home, the work should be zero-rated for VAT.

You’ll still have to pay the standard VAT rate (20%) if you buy the insulation yourself from, say, a builder’s merchant. But if you then contract someone to fit it, they can zero-rate their installation service.

The 0% VAT rule for energy saving materials applies across Great Britan and Northern Ireland, and is due to run until 31st March 2027 (after which it will switch to a 5% reduced rate).

Main image: Roll-out blanket insulation is the go-to option for upgrading a loft, as it’s simple and cost-effective to install. Photo: ISTOCK.COM/STURTI

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