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Loft insulation

A guide to loft insulation

published: 11 December 2019
Read time: 5 minutes

Insulating your loft will almost certainly save you a packet – often within a couple of years

Do I need loft insulation?

If you have a loft and it isn’t insulated, getting it sorted is one of the easiest and most effective ways to cut down on your household expenses. Loft insulation can save you hundreds of pounds in heating bills a year – and it might help save the planet too.

About a quarter of all the heat lost from a house escapes through the roof. Loft insulation is like a woolly hat for your house, keeping the warm air in so you need less energy for heating. That way, the property is cosier and you’ll spend less on energy.

According to the Department for Energy and Climate Change, of the 28.4 million properties in Great Britain, 24.5 million have a loft – but only 16.2 million have loft insulation. That means 34% of people with a loft could start saving serious money by getting their lofts insulated.

Savings from loft insulation Man insulating a loft

How does loft insulation work?

Most lofts are insulated with rolls of foil-backed felt or mineral fibre. These work like blankets, keeping warmer air inside your house. Sometimes polyurethane foam or mineral wool might be sprayed into tricky-to-reach areas.

Insulation is usually installed between the joists in your loft. This stops the heat from your home rising into the loft, and it’s quick and easy to install yourself if you want to try some DIY. This type is known as ‘cold loft’ insulation.

If you have a loft conversion, or if you want to keep your loft heated, insulation can also be fitted to the inside of your roof. This is known as ‘warm loft’ insulation. It’s a bit trickier to do though, and probably best left to a professional.

If your loft is difficult to access from within your house, or if it has some hard-to-reach corners, you can also use loose-fill insulation. Some loose-fill insulation – which can be made from cork granules or even recycled newspapers – is available at DIY stores, and it’s easy to install yourself. Or you might want a professional to use specialised equipment to install blown-fibre or polyurethane foam.

How much loft insulation do I need?

It’s recommended that you insulate your loft to a depth of 250 to 270 mm.

Even if you already have loft insulation, it’s worth checking to see how much you currently have, as the guidelines have increased – not so long ago, 100 mm was considered enough. If you’ve had loft insulation for a while, you might still be paying too much for energy, and adding more insulation could save you a significant amount of money.

How much does loft insulation cost?

According to the Energy Saving Trust, the typical cost of loft insulation in an average semi-detached house is £300. Depending on your home, this could be more or less: the price goes up to £395 for a detached house and down to £285 if you live on a terrace.

This might be an expense, but the savings are significant. Insulating your loft can knock around £225 a year off your energy bills in a detached house, and £135 in a semi. This means that in around two years, your insulation will have already paid for itself – and every year after, it’ll keep on saving you money.

If you’re a DIY enthusiast, you could save money by installing loft insulation yourself – but that’s probably only a good idea if your loft is easily accessible and you’re insulating between the joists, rather than the inside of the roof.

Does loft insulation cut my carbon footprint?

Loft insulation doesn’t just save you money – it can also reduce your household’s carbon emissions.

Insulating a detached house to 270 mm saves 990 kg of CO2 every year – that’s roughly the equivalent of one return flight from London to New York. If you live in a semi-detached house or on a terrace, you’ll save 550 to 580 kg of carbon dioxide a year.

Can I use my loft for storage with loft insulation?

Many people use their lofts as storage space, but you can’t put boxes on or even lay boards over the insulation – if it gets squashed, it won’t be effective.

One option is to buy insulation boards topped with a wood or polystyrene layer, which are available in some DIY stores – but even then, your insulation won’t work as well. Alternately, you could raise the floor in your loft and fit insulation underneath.

How do I insulate a loft conversion?

If you use your loft as a living space, you will have to insulate the inside of the roof rather than the loft floor. Roof or ‘warm loft’ insulation is more expensive to install than ordinary insulation, but it’ll save you even more on heating, and keep your loft snug and warm.

Roof insulation usually works by fixing rigid insulation boards between the roof’s rafters. They have to fit snugly between the rafters, otherwise warm air will still escape through the roof. This is a tougher job than ordinary loft insulation, and there’s a risk it could lead to damp, so it’s probably a good idea to spend a bit more for a professional installation.

Does a flat roof need insulation?

If you live in a house with a flat roof, heat will still escape up through the roof, and you can still save money by getting it insulated. Flat-roof insulation is usually installed from above, and requires specialised materials. As a result, it’s usually tougher and more expensive to install – but once it’s in place, you should see the same savings as with a peaked roof.

Do I need to insulate my pipes?

If you get ordinary cold-loft insulation, it’s important to make sure that any pipes in your loft are also insulated. Because insulation stops heat rising into your loft, it will get much colder in there, and this cause pipes to freeze or burst in the winter months.

Pipe insulation is cheap and easy to find, and you can easily fit it yourself. You should also make sure you insulate your water tank if you have one in your loft. Insulate the top and sides of your water tank, but never insulate underneath – without some heat coming from below, it’s more likely to freeze or burst in winter.

The only exception is if your water tank is raised 10 cm or more above your loft insulation, in which case you can insulate its underside.

Can I get loft insulation for free?

If you receive certain benefits, you may be able to get insulate your loft for free under the Energy Company Obligations (ECO) scheme. Some of the benefits that qualify you for free insulation under ECO include:

  • Universal Credit

  • Jobseeker’s Allowance

  • Disability Living Allowance

  • Income Support

  • Child Tax Credit (if you’re also below a certain income level)

Not all energy providers will offer you free insulation – but some will help insulate your loft for free even if you aren’t a customer. Depending on your circumstances and your provider, you might get insulation installed entirely for free, or you may get a partial grant to cover some of your costs.

Keep in mind that most providers will only cover some kinds of insulation. In general, you can get a grant for ordinary ‘cold loft’ insulation, but you’re less likely to get free insulation if you want warm-loft insulation or to insulate a flat roof.

The ECO scheme only operates in England, Scotland and Wales. If you’re in Northern Ireland, you may be able to get free insulation by contacting the Bryson Energy advice line.

Where can I 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.

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