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Why get insulation?

  • Improve your home's thermal efficiency
  • Save on your energy bills
  • Slash your carbon footprint

The ultimate guide to loft and roof insulation

Loft insulation will typically save you £355 per year

It can cut more than a tonne of CO2 from your carbon footprint

The insulation will typically be effective for at least 40 years

We understand why you’d be interested in loft and roof insulation – after all, a quarter of your home’s heat is lost through the roof (source: Energy Saving Trust).  

As well as retaining heat, loft insulation will also typically save you £355 per year and cut your annual CO2 emissions by 0.6 tonnes.

There’s never a better time than now to get insulation that typically lasts for 40 years – at least.

Let’s see which type of insulation suits your loft and roof, and how you can go about making your home warmer while cutting your energy bills – and if you’d like to see how much spray foam insulation will set you back, just fill in this quick form.

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woman installs loft insulation

What is loft insulation?

Loft insulation is a shield you can install between the loft and the rest of your home – to keep the warmth in the rooms below – and on the underside of the roof, to retain your loft’s heat.

The insulating material you use will usually be made of mineral wool, organic foam, or rigid insulation boards.

You or a professional will fit this material between your rafters – which are the beams on your roof – or your joists, which are the beams on your loft floor.

Types of loft insulation

There are a few different types of loft insulation, but finding the one for your space is relatively easy.

You can make the decision based on your roof’s shape, the shape and condition of your loft, and the loft’s intended use. Let’s run through the options.

Storage space

If you see your loft as a place to keep your suitcases, children’s baby clothes, or old family memorabilia, you’ll want to rest these useful or precious items on a flat surface.

For this, you need to lay down some boards, after fitting some mineral wool insulation between your joists.

Unfortunately, your joists won’t be high enough for you to install a sufficient amount of insulation (unless you also have warm loft insulation – more on that later).

To solve this problem, you can buy wooden battens to lay across your joists, or plastic legs that can stand on your joists. Either of these will create more space for insulation between your joists and boards.

Make sure you don’t push your insulation material down when you fit the boards, as this can make it less effective, and leave a ventilated air gap above your insulation.

If you don’t, condensation could gather on the bottom of the boards and leave you with a damp problem.

If you’re not comfortable carrying out any of these steps, hire a professional.

Warm loft

Instead of going above the rafters, you could get a professional to fit some insulation between or below them.

They will either use rigid insulation boards that have been cut to fill the spaces between your rafters, or spray foam insulation in those gaps instead.

This will stop heat getting out of your home through the roof, plus it’s more effective than the standard loft insulation outlined above – meaning you can stop worrying about your pipes and water tanks freezing over.

Because of this extra warmth, you’ll also be able to board over your loft floor insulation without having to buy wooden battens or plastic legs to fit in more insulating material.

The downside is that this method is typically more expensive, both because of the benefits, and because any chimneys, gable walls, or party walls need to be insulated at the same time for it to be effective – which can be a lot of work.


Maybe you want some privacy from the kids. Maybe you want the kids to have some privacy from you. Maybe you’re Rochester from Jane Eyre.

In any case, getting your loft insulated is a quick way to turn it into an extra bedroom.

Because lofts are external facing on all sides, you’ll need a professional to insulate all the walls and the ceiling, so that it’s warm enough to live in.

If you have a sloped roof, your chosen expert will use the warm loft method described above, but add a layer of plasterboard to the inside, so you can decorate the room to your taste. Vertical walls can be insulated in the same way.

If you have a flat roof, scroll down to see what that insulation installation will entail.

Your professional installer should create enough ventilation to prevent any damp and insulate all areas around any dormer windows, but you’ll need to make sure the window itself has double glazing. You can find out how much this will set you back by visiting our Double Glazing Costs page. 

Inaccessible space

No-one aspires to have an inaccessible loft space, but sometimes you don’t get a choice.

In this case, you can hire a professional who will use tubes to blow insulation into the loft, thus keeping the warmth where you need it – in accessible spaces.

The insulation will typically consist of mineral wool, organic foam, or treated cellulose – but most importantly, it’ll retain more heat while cutting your energy bills and emissions.

Flat roof

Let’s emphasise the most important point first: don’t attempt to insulate a flat roof yourself.

Flat roofs should be insulated from above, meaning the installation would require you to stand on your home – a dangerous act for an amateur.

It also calls for a high level of expertise, to ensure it’s both effective and compliant with the latest regulations.

The expert you hire will either lay a rigid insulation board on top of your roof’s weatherproof layer, or directly onto the rafters below it.

The invasive nature of this installation means you should probably save it for when your roof covering needs to be replaced for other reasons.

insulation on a loft floor

Things to consider when choosing loft and roof insulation

If the above section left you with more questions than answers, here are some points to bear in mind.

They should help you to come to a decision – and if you’re still not sure, consult a professional.

What is your loft’s purpose?

We know this is a heavy question, but it’s also the most important one.

After all, as outlined above, the type of insulation you choose depends entirely on what you want your loft to be.

Do you want it to be a storage space, a bedroom, or simply a barrier between your home and the cold winds of the outside world?

You might want to cut down on energy wastage, install another bathroom, or create a livable space where your teenager can feel comfortable, but independent. It’s up to you.

Sometimes, insulation makes a space colder

Insulating the floor of your loft is a double-edged sword: it’ll keep the rest of your home warm, but your loft will be colder.

This means any pipes or water tanks you have in the loft could freeze – so make sure to insulate them.

If you’re interested in making the space comfortable to be in, insulating your roof should achieve this, as long as your loft is heated.

Don’t let your loft become a damp squib

Planning to embark on a DIY installation? Get a professional assessment to check for damp.

Insulating your loft could introduce or exacerbate damp, which is the last thing you want. An expert will be able to tell you how to ensure your loft has enough ventilation to avoid disaster.

And if you’re worried about how much this could cost, we have good news for you in the next section.

Loft and roof insulation grants

If you can get a helping hand when making home improvements, that’s always a plus.

Thankfully, there’s a grant which can chop hundreds of pounds off the cost of roof and loft insulation: the Energy Companies Obligation scheme.

Energy Companies Obligation scheme (ECO)

Since 2013, ECO has compelled large UK companies to provide low-income homes and people on certain benefits with heat-saving methods – including loft and roof insulation.

You may qualify for the scheme if you’re on one of a range of benefits, including the Pension Guarantee Credit, Tax Credits, and Universal Credit. The full list is available here.

It’s also worth mentioning the Affordable Warmth Obligation scheme (AWO), which you may see while you’re looking for government grants. Don’t be confused – it’s now exactly the same as the ECO scheme.

Green Homes Grant

Unfortunately, the Green Homes Grant was closed on 31 March 2021.

The £2 billion government scheme was intended to provide 600,000 homes with vouchers of at least £5,000 towards eco-friendly home improvements, but fell short of this target by a mind-boggling 93.5%.

Roof and loft insulation cost

Roof and loft insulation costs tend to vary, depending on a number of factors. Overall, it’s usually much cheaper than many other home improvements, typically costing between £455 and £640, according to the EST.

You can expect savings of £355 per year, meaning you should recoup your initial expense in less than two years.

Roof and loft insulation savings

Insulating the upper reaches of your home will save a semi-detached household £355 per year on average, according to the EST.

And you’ll rack up more than just financial savings. You could cut your carbon footprint by 0.6 tonnes of CO2.

That sounds like a lot – and it is.

The UK emits more than 400 million tonnes of CO2e* per year, according to the latest government data, which works out to 6.3 tonnes per person.

If you save 0.6 tonnes of that total, you’ll reduce your carbon emissions by 10%, typically – all while enjoying a warmer home with lower energy bills.

*carbon dioxide equivalent, a measurement that converts all greenhouse emissions into CO2 terms


There’s never been a better time to insulate your roof and loft.

Modern methods of insulation can allow you to save hundreds of pounds per year and substantially cut your carbon emissions.

Whether you want to create an extra bedroom, a games room, or some much-needed storage space, having a habitable loft is always an advantage – plus it can add value to your property.

If you haven’t insulated your loft or roof, now is the time. If you’d like to jump on the bandwagon, you can fill in this form to see how much spray foam insulation would cost you.

Written by:
josh jackman
Josh has written about eco-friendly home improvements and climate change for the past four years. His work has been displayed on the front page of the Financial Times, he's been interviewed by BBC One's Rip-Off Britain, and he regularly features in The Telegraph and on BBC Radio.
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