Loft insulation

Save energy through loft insulation

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If your loft isn’t insulated properly, you could be losing a quarter of your home’s heat through the roof.

Man insulating a loft

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Loft insulation is a bit like a woolly hat for your house, keeping the warm air in so the property is cosier and the energy bills are cheaper.

How much does it cost?

Loft insulation is usually quick and easy to install, and lasts for about 40 years. It typically costs between £300 and £400, but you could save up to £250 a year on your energy bills, so it would pay for itself after a couple of years. If you’re a DIY enthusiast, you could even tackle the job yourself, though it’s probably only a good idea if your loft is easily accessible, and your home doesn’t suffer from damp.

How does it work?

Most lofts are insulated with rolls of foil-backed felt or mineral fibre, which are a bit like blankets. The first layer is fitted between the joists and a second layer is ideally put down across the joists at right angles. The insulation basically stops the heat from your home rising up into the loft.

The recommended depth is 270mm, so if you already have some loft insulation you can simply top it up to the necessary thickness. You can buy blanket insulation from most DIY stores, and you should always follow the manufacturer’s instructions.

Loose fill insulation can be useful for topping up existing insulation or for insulating awkward spaces. Some professional firms also install blown-fibre insulation using special equipment. The process should only take a few hours, and it can be particularly useful if your loft is difficult to access.

What if I use my loft for storage?

Many people use the loft as a storage space, but you can’t put boxes on or even lay boards over the insulation or it won’t be effective. You either have to place insulation boards on top of the joists, or raise the floor level so that you can fit enough insulation beneath the new floor. Just be careful not to squash any insulation, otherwise it won’t do the job properly.

Roof insulation

If you use your loft as a living space, you will almost certainly have to insulate the roof rather than the loft floor. You can normally do this by fixing rigid insulation boards between the roof rafters. They must fit snugly, and can then be covered with plasterboard. You might even want to consider insulated plasterboard, particularly if the rafters aren't very deep.

Insulating a flat roof

It’s a bit trickier to insulate a flat roof, and you’ll need to employ a professional. A flat roof is normally insulated from above, by putting rigid insulation board either on top of the roof's weatherproof layer or on top of the timber roof and adding a new weatherproof layer on top.

Find a professional

If you need a professional to insulate your loft or roof, look for a company that’s a member of the National Insulation Association (NIA). The website ( has more information, and can help you find an NIA installer in your area.

Pipes and tanks

Don’t forget to insulate any pipes or water tanks in your loft. It’s also a good idea to fit an insulated loft hatch, or put some draught excluder around the hatch.

Help with insulation costs

Some energy companies offer free loft insulation to certain eligible households. You normally have to be receiving income-related benefits to qualify for financial help, but it’s worth finding out the details from the company’s website. You don’t always have to be a customer, either. So if your own supplier doesn’t offer help, you could contact another one.

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