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  • Improve your home's thermal efficiency
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The 5 Best Types of Loft Insulation

Spray foam insulation is very effective, but it’s also expensive

Loose fill and blanket insulation are good for lofts with suspended floors

Blown fibre insulation is a more eco-friendly alternative to spray foam 

Insulating a loft can be expensive, with the cost of spray foam insulation often going over £1,000. Luckily, it’s not the only option.

In this article, we’ll explain what the five best types of loft insulation are. We’ll assess their pros and cons, and tell you how much each of them costs.

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man wearing protective clothing spraying cellulose fibre insulation on wooden walls of loft

What are the best types of loft insulation?

The five best types of loft insulation are spray foam insulation, blown fibre insulation, blanket insulation, loose fill insulation, and sheet insulation.

Spray foam, blown fibre, and sheet insulation are all applied to the inner roof of the loft, whilst blanket and loose fill insulation are installed in the floor.

For a full breakdown of loft insulation costs, go to our page.

Spray foam insulation

Spray foam insulation is made from polyurethane, a synthetic material. It’s typically sprayed in the form of foam on the inner roof of a loft, between the beams.

There are two types of spray foam: closed-cell foam and open-cell foam. Closed-cell foam is more dense than open-cell foam, and expands then hardens after it’s applied.

Open-cell foam is less dense than closed-cell foam. It doesn’t expand as much when it’s applied and has a spongy texture when dry.

The main advantage of spray foam insulation is that it’s highly effective at keeping heat inside the loft – more so than other types of insulation.

On the downside, its airtight structure can sometimes lead to issues with damp, which has made some mortgage lenders refuse to lend money to homes that have spray foam.

Spray foam insulation costs around £20 to £50 per square metre, making it one of the more expensive types of insulation.

Pros and cons of spray foam insulation


  • More effective at keeping heat in than other types of insulation
  • Flexible, can be applied in difficult to reach areas
  • Lasts up to 80 years


  • One of the most expensive insulation types
  • Can cause issues with damp
  • Some mortgage lenders won’t lend to homes with spray foam insulation

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Blown fibre insulation

Blown fibre insulation, also called blown-in insulation, is similar to spray foam insulation in the sense that it’s sprayed onto the inner roof of a loft. What’s different are the materials it’s made of.

The main types of materials used for blown fibre insulation are fibreglass (recycled glass particles), mineral wool (stone or glass particles), and cellulose (paper fibres).

Fibreglass is typically the preferred material when it comes to blown fibre insulation since it’s less prone to mould growth.

Blown fibre is generally a little cheaper than spray foam insulation, costing £6 to £50 depending on the material. It’s made from natural materials, so it also has the advantage of being more eco-friendly than synthetic spray foam.

Pros and cons of blown fibre insulation


  • Eco-friendly options available
  • Flexible, can be applied in difficult to reach areas
  • One of the most effective types of insulation


  • Certain materials can be prone to mould
  • One of the more expensive types of insulation
  • Messy to install since fibre particles can cause dust when being applied
rolls of wool blanket insulation piled on top of one another in wooden loft

Blanket insulation

Blanket insulation is a type of floor insulation that’s very easy to install in a loft. It typically comes in thick rolls or sheets, made from materials such as fibreglass, mineral wool, plastic fibres, or sheep’s wool.

Installing it involves placing the insulating rolls between the floor joists (the beams in the floor) and securing everything with netting.

It costs around £5 per square metres, making it one of the cheapest types of insulation.

The main downside to blanket insulation is that it’s not as effective as other types of insulation. Achieving your desired levels of heat retention might require you to use several sheets of material.

Pros and cons of blanket insulation


  • One of the cheapest forms of insulation
  • Easy to install, can be a DIY project


  • Not as good at retaining heat as other forms of insulation
  • Takes up a lot of space, and not all loft floors are suitable for it

Loose fill insulation

Loose fill insulation consists of loose granules, which can be made from cork, mineral wool, or cellulose fibre. These granules are poured in between the floor joists, and can be used on their own, or in addition to existing insulation.

The advantage of loose fill insulation is that it’s relatively cheap – it costs around £20 to £30 per square metre – and easy to install. The main downside is it has a tendency to compress over time, which will reduce its thermal resistance – that is, its insulating capabilities.

It can also be prone to absorbing water, which can cause damp and mould. This is why it’s important to get loose fill insulation that’s been treated with anti-mould solutions.

Pros and cons of loose fill insulation


  • Relatively inexpensive
  • Easy to install
  • Can fit into tight, hard to access spaces


  • Can make a mess when being installed
  • Compresses over time and loses thermal resistance
  • Can be prone to absorb water and cause mould

Sheet insulation

Sheet insulation comes in the form of rigid sheets or boards, which can be made of synthetic materials such as polystyrene, or natural materials like mineral wool.

These sheets are stuck to the inner roof of the loft with a flexible sealant.

It cost around £35 per square metre, making it one of the pricier types of loft insulation.

One advantage of sheet insulation is that the sheets can be cut to size, so they fit into all the nooks and bends of the loft roof.

However, doing this correctly can be tricky, and requires a professional.

Sheet insulation is also good at controlling moisture, and sheets made from expanded polystyrene can act as a vapour barrier, stopping moisture from entering the home.

Pros and cons of sheet insulation


  • Can be cut to fit unique roof shapes
  • Good at controlling moisture


  • On the expensive side
  • Requires a professional in order to be properly fitted

What’s the best type of loft insulation?

There’s no best type of loft insulation. Finding the option that’s right for you depends on your budget, the layout of your loft, and your personal preferences.

If your main concern is having a very tightly insulated loft, then spray foam insulation or blown fibre insulation are the best options, since they’re the best at stopping heat from escaping.

However, they’re also expensive, and if your budget is limited, you might prefer a cheaper option, such as blanket insulation or loose fill insulation. Both are still great at keeping heat in, even if they don’t create quite as tight of a seal as other insulation types.

If your loft doesn’t have suspended floors, then blanket insulation or loose fill won’t be possible to install, even if you wanted them. But that doesn't mean you have to fork out more money than you’d like on blown fibre insulation. Sheet insulation – which goes on the inner roof – is a reasonably priced and effective alternative.


Insulating your loft is a great way to preserve heat in your home and keep your energy bills down.

After all, a quarter of all household heat is lost through the roof in uninsulated homes, according to the Energy Saving Trust.

If you want to get a quote for spray foam insulation, just fill in our form. We’ll pass your details onto professional installers, who’ll reach out to you with their best prices.

Best loft insulation: FAQs

The recommended thickness of insulation in a loft is 270 millimetres (mm) for optimal results, although insulation that’s 200 mm thick will still make a big difference. At the end of the day, any insulation is better than none.

If your old insulation is still in good condition, there’s no reason to remove it.

However, if you see signs of mould, pests, or notice an odd smell coming from your old loft insulation, it’s best to get it removed by a professional. Mould and damp can spread to your home and damage its structural integrity, and no-one wants pests.

It’s best not to put insulation too close to any light fixtures or other electrical wires in your loft. This can create a fire hazard, and damage the electrical wires. It’s also important to not block any vents with your insulation – they’re there for a reason, after all.
Written by:
Tatiana has written about multiple environmental topics, including heat pumps, energy-efficient household products, and solar panels. She is dedicated to demystifying green tech to make eco-friendly living more accessible.
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