18th Nov 2022 -

Within a house, heat is continually lost through the loft and roof of a building. Thankfully, there is a range of high quality loft insulation options, which can cut your energy bill by up to 20%. Loft insulation is installed within the joists of your loft space, offering high levels of thermal insulation. Properly insulating your loft will increase the heat retention in your house, increasing its energy efficiency and lowering your heating bills. This brings environmental benefits as well as financial ones.

In this guide from Building Materials Nationwide, we’ll talk you through the various options available in loft insulation. We’ll look at the average cost of loft insulation per metre2, and we’ll cover whether it can be installed yourself or whether you’ll need a contractor. Finally, we’ll look at whether you could be eligible for a government grant to cover the loft insulation costs in your house.

Your Options For Loft Insulation

When it comes to loft insulation, there are several options available to you that offer their benefits and disadvantages. The most common form of loft insulation historically is blanket insulation, rolls or slabs designed to be fitted between the joists in a loft. These can be made from a variety of materials including mineral wools or sheep's wool. They can be quickly installed and offer quality, long-lasting thermal insulation.

You can also install loose-fill insulation within a loft. Loose-fill insulation is poured between the joists of a loft, offering some thermal insulation. An advantage of loose-fill insulation is its cost-effectiveness. With certain loose-fill materials, you will need to use safety equipment when installing, to avoid breathing in dangerous fibres.

A different option is to use insulation boards, which are used on the sloping sides of a roof rather than on the joists. This offers higher-quality insulation for your home but comes at a premium cost. A benefit of insulation boards is that the loft space itself will be insulated and available for use. 

Blown-fibre insulation, known as spray foam insulation, involves spraying bonded loose insulation into all areas of your loft. Unlike loose-fill, this requires specialist equipment operated by a professional to install. A risk with blown fibre is that it can reduce ventilation in a loft space, which can increase humidity and dampness. Over time this can damage your roof timbers. It also can’t be decorated over, so if you are looking to use your loft for any purpose this may not be suitable.

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The Average Loft Insulation Costs per M2

For blanket insulation and loose-fill insulation, you will be looking to cover the entire floor area of your loft, fitting between the joists. For insulation boards, you will need to cover all sloping edges of the roof. Spray foam insulation covers the entire loft, including the floor and roof.

In terms of cost per m2, you will be looking at around £5 per m2 in blanket insulation, £7.50 per m2 in loose-fill insulation, £10 per m2 for insulation boards and £55 per m2 for blown-fibre insulation, which includes installation. These prices per square metre are all approximate but show the added cost that comes with using blown-fibre insulation.

Installing Yourself vs Using a Contractor 

With DIY experience, it is possible to install blankets, loose-fill and boards yourself. Blanket insulation comes in a range of widths, so you should first measure the distance between your loft joists before buying an appropriate-sized roll or slab. Blanket insulation should be cut with scissors, making sure to not stretch or tear it. The recommended height of loft insulation is 270mm, which will often be higher than the height of your loft joists. You should never compress blanket insulation, so if you wish to use boarding within your loft you should use loft legs, which can be fitted to the joists, allowing for the sturdy installation of a raised loft floor above them.

Loose-fill insulation can be poured into the spaces between joists in your loft. Depending on your choice of loose-fill insulation you may need to use safety equipment. It should be filled to a depth of about 200mm, so you should check the height of your joists before choosing this insulation method, to make sure they can support it. Loose-fill should be carefully brushed to give an even height across your loft floor, and if left uncovered should be checked on occasion to make sure it hasn’t been unsettled.

A construction worker wearing white overalls with a white face mask and gloves fitting Kingspan insulation within a floor loft space.

You have two options for fitting insulation boards under your roof, either securing them between rafters or underneath them. Securing them underneath is preferable if you have the space, as you won’t have to leave any gaps for air to circulate. Boards can be cut to size and attached to your rafters using a nail gun. If you wish to install loft insulation boards between rafters, you will have to leave a gap of 50mm between the board and your roof's membrane. You can do this by affixing wooden battens to the rafters, leaving a small gap before you attach the board.

Blown-fibre is a job for an insulation specialist, requiring professional equipment and the ability to evenly spread the insulation within your loft. You will be looking at costs of roughly £55 per square metre for insulation. 

If you wish to use a labourer to install insulation blankets, loose-fill insulation, or insulation boards, you will be looking at a day rate of around £150-£200. There could be additional costs for things like removing damaged insulation or insulating a loft hatch. If you are looking for loft insulation and boarding this will also increase the costs. In some cases, electrical wiring will have to be moved rather than installed within loft insulation. Houses insulated before the millennium will sometimes contain asbestos insulation in their lofts. If you have any concerns about the insulation in your loft, hire a professional to have it checked and removed. 

Are you Eligible for Free Loft Insulation?

Within the UK, there is a government-run scheme known as Energy Company Obligations, through which large energy suppliers can give up to £1000 towards loft insulation costs for their customers. Any energy supplier serving more than 150,000 customers is required to take part in this scheme. If you own your own home (or rent in limited cases) and are receiving certain benefits, such as universal credit, carer’s allowance, or disability living allowance, you could be eligible. Contact your energy company before paying for loft insulation, to see whether you could qualify for a grant, helping you to save money while lowering your energy bills.

Our Comprehensive Range of Loft Insulation

At Building Materials Nationwide, we stock a wide range of loft insulation. If you are looking for blanket insulation between the joists of your loft, we have a range of high-quality rolls and slabs in stock. We also offer insulation boards for use within a loft space, and loose-fill insulation. If you are looking for acoustic loft insulation, we also stock a range. We offer delivery across the UK on all of our products.

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