Guide to Roof Insulation Cost in the UK

The average cost of roof insulation in this guide is correct as of January 3rd 2024

If you want to retain heat within your home and save money on your energy bills, installing roof insulation is crucial! But how much does roof insulation cost? That is the question I'm going to help you answer today!

The cost of insulating a roof will depend on the size of your property, the materials you choose, and your budget. I've put together this free guide to roof insulation costs to help you get a better idea about the costs involved.

My job as the Roof Advisor is to crunch numbers, scour the Internet and find you the best prices.

Roof Insulation Cost
Roof Insulation Specialist

What Are The Average Roof Insulation Costs In The UK?

The average cost of installing roof insulation in the UK is around £500. Keep in mind that this is an average cost and not the actual cost. There are many variables to take into consideration when trying to calculate the cost of roof insulation.

Identifying what type of roof you have and the materials used are essential for calculating roof insulation cost. Once you have determined what kind of roof you have, you can choose what type of roof insulation material you would like to use.

Most UK homes have a pitched roof. If you're not sure what this type of roof looks like, see the picture below this paragraph. You'll see that a pitched roof has two sloping sides to it and one straight ridge across the top.

There are two different ways to insulate a roof. The first way is to lay the insulation above the roof joists. The second way is to fix the insulation directly under the sloping roof. Your roof insulation costs will depend on which insulation method you choose.

Once you have chosen your method of insulation, it's time to decide what type of roof insulation you want to use. There are several options available to you, and the price can vary quite a lot. At this point, I would suggest you figure out your budget and choose a roof insulation material that fits within your budget.

If you are considering hiring a professional tradesperson to install your roof insulation, I highly recommend you go here to get the best prices. Hiring a professional to do the work for you will make your life easier and less stressful. The tradesmen will come to your home, measure up, let you know exactly how much insulation you need and how much it will cost. And they will do all the hard work for you, while you relax and watch the TV or mow the lawn.

Insulating a Roof
Insulating a Roof

What Are The Best Roof Insulation Materials To Use To Insulate A Roof?

Some of the best roof insulation materials to use are foil backed polystyrene roof panels, roof insulation boards, spray foam, glass wool, and rock wool. Each type of insulation has its own unique benefits. Ultimately, the one you choose will probably come down to the size of your roof and your budget.

If you want to know more about each type of roofing insulation, or how much roof insulation cost see the information and the tables below.

Best Roof Insulation Materials

Once you have identified what type of roof you have, the next step is to choose your roofing insulation material. Choosing the most suitable type of insulation for a roof will mostly depend on your budget. To get an accurate price for roof insulation, you will need to measure the area and work out how much insulation you will need. Below you will find the most popular types of roof insulation materials and their costs.

Whichever type of insulation you choose, its sure to improve the energy efficiency of your home.

1. Fibreglass Insulation

One of the most popular types of roof insulation material is fibre glass, and with good reason. Apart from being lightweight and offering a good level of insulation, the cost of fibre glass for roof insulation is relatively cheap. It's important to know that you must install roofing underlay before installing glass wool insulation. Finish the job properly by installing a vapour barrier to stop the insulation from absorbing moisture from the room.

The average cost of fibreglass roof insulation per square metre is approximately £10.

You should expect to pay around £20 per square metre for a tradesperson to supply and install fibreglass roof insulation.

Note: fibreglass can cause skin irritation during the installation if you plan to do it yourself.

2. Rock Wool

If sound insulation is important to you, then rock wool would be more suitable for your requirements. Rock wool provides a good level of roof insulation as well as reducing sound. The cost of rock wool roof insulation is more expensive than glass wool because it is made from volcanic rock. The volcanic rock is heated to an ultrahigh temperature to create a dense, spongy material.

The average cost of rock wool roof insulation is around £20 per square metre. If you are going to hire a professional to install it for you, expect to pay around £30 per square metre (price includes supply and installation).

Note: as with glass wool, rock wool can cause skin irritation during installation.

Rock Wool Roof Insulation Cost
Rock Wool Insulation

3. Spray Foam Insulation (PUR)

Spray foam roof insulation is the quickest and most efficient way to insulate a roof. It's easy to spray the foam into every nook and cranny of the roof. Even those hard to reach gaps are filled effortlessly when using spray foam roof insulation. A spray gun is used to spray the foam onto a surface. Once the foam has landed on a surface, it immediately expands to create an even layer of insulation.

Spray foam insulation costs are around £30 per square metre. Unfortunately, spray foam is not a DIY job. Hazardous gases are released during the spraying, and for this reason, only a trained professional should carry out the work.

Spray Foam Roof Insulation Cost

4. Insulation Panels / Insulation Boards

One of the best methods to insulate a roof is to use insulation boards. The boards have a 1.5 inch diameter and provide a high level of insulation. Boards are easy to install, and you can buy them in a variety of sizes. Using boards will allow you to insulate a roof regardless of its size quickly. Another bonus to using boards to insulate a roof is their acoustic qualities. Not only do the boards retain heat within your home, but they also help to repel noise.

The average cost of using roof insulation boards to insulate a roof is about £11 per square metre. If you are going to hire a professional to install the boards for you, expect to pay anywhere between £20 – £25 per square metre (this price includes the cost of the boards).

If you are thinking of buying roof insulation online, I highly recommend this website. The prices are very competitive, and the quality is superb. I doubt you will find another site that offers quality insulation at these prices.

Pitched Roof Insulation Costs

The majority of homes in the UK have a pitched roof, so there is a good chance you have one too. The average cost of insulating a pitched roof in the UK will depend on what roofing insulation material you choose and the size of your roof. The cost of insulating a roof will also depend on whether you are going to do the work yourself or hire a professional to do it for you.

If you plan to do the work yourself, then you really should take the time to read this guide in depth, so you get a good idea of what is involved. Please scroll down to the section headlined DIY roof insulation.

Pitched Roof Insulation
Houses with a pitched roof

While you’re planning to insulate your roof, now would be a good time to inspect the condition of your roof. Can you see daylight from the inside of your roof space? If you can, now might be the best time to find out how much a new roof cost.

Whether you plan to carry out the work yourself or hire professional insulation specialists, this guide will help you calculate roof insulation costs.

Flat Roof Insulation Costs

The cost of insulating a flat roof will depend on which insulation method you choose and the amount of roofing insulation required.

One option would be to use warm deck insulation. This type of flat roof insulation is fitted above the roof's deck but underneath the weatherproof layer.

A second option would be to use a cold deck fitted underneath the joists and has enough space for ventilation.

A third option is to use inverted roof insulation. The most common type of inverted roof insulation is a layer of gravel placed on top of a weatherproof layer.

Flat roof insulation costs around £35 per square metre (using warm or cold deck insulation). However, prices rise quite a lot if you opt to use exterior flat roof insulation. The cost of insulating a flat roof with external insulation works out at around £80 per square metre.

If your flat roof is over ten years old, or you have an asbestos garage roof, you might want to think about a flat roof replacement. Replacing an old flat roof and insulating it at the same time might be a better idea for the long run.

Flat Roof Insulation Cost

Average Prices To Install Roof Insulation In The UK

As I've mentioned several times above, roofing insulation costs are determined by your budget, the size of your roof, and your choice of insulation. If you want to calculate roof insulation costs, you're going to have to get your tape measure out and measure the area you plan to insulate. Measure the length and the width of the area to determine how many square meters of roofing insulation you need.

To make life a little easier for you, I have created a few examples of roof insulation prices in the table below.

Please note that these prices are only meant to be used as a guideline and are not the actual prices you are likely to pay. If you would like to get an accurate roof insulation quote, I highly recommend you visit this website.

Warm Deck Insulation Board20 Square MetresFlat Roof1-2 Days£600-£700
Spray Insulation20 Square MetresPitched Roof1 Day or Less£695-£900
Fibreglass Insulation20 Square MetresPitched Roof 1 Day or Less £370-£430
Mineral wool Rolls20 Square MetresPitched Room1-2 Days£395 – £490

Average Cost of Materials Without Labour

The table below gives you some idea about the costs of materials for insulating a roof. The example prices below show the average roof insulation prices without labour.

Warm Deck Insulation Board£15 – £20
Mineral Wool Rolls£5 – £9
Spray Insulation£20 – £30
Fibreglass Insulation£4 – £6

Time Scales & Labour Costs

Labour costs will depend on where about in the country you live. You should expect to pay somewhere around £150 -£200 per day per tradesperson. The amount of time it takes to complete the job will determine the final roofing insulation cost. It usually takes between one and two days to finish installing roof insulation in an average sized roof. It's likely to take longer for larger roofs.

Warm Deck Insulation Board20 Square MetresPitched Roof1-2 Days
Mineral Wool Rolls20 Square MetresPitched Room1-2 Days
Fibreglass Insulation20 Square MetresPitched Roof1 Day or Less
Spray Insulation20 Square MetresFlat Roof1 Day or Less

Would you like a FREE no obligation quote for roof insulation? If you answered yes, click on this link and pop your details into the quote form. It will only take about 45 seconds, and you will have your quotes in no time!

DIY Roof Insulation

If you know your way around a toolbox and know about health and safety, it's not too difficult to install roof insulation by yourself. However, if you're not confident working with measurements and power tools, it might be a better idea to hire a professional to do it for you. If you're sure about your skills and want to pursue the DIY route, keep reading.

Although installing roof insulation is a pretty straightforward job, there are certain steps you need to take to make sure the job is done properly.

Listen. This is important. The consequences of not following the steps below could be extremely costly. So I advise you to listen.

The first step is to clear the area and make sure there are no obstructions in your way. Once the area is clear, inspect timbers for any signs of damp, condensation, or wood rot. Now is the time to detect and treat these issues before they get out of hand and destroy all of your hard work.

The best place to get damp and condensation treatments are here.

The second step is to locate any electrical cables and make sure they are exposed. You don't want to cover electrical wires with insulation and risk them overheating.

The third step is to make sure that any existing pipework in the roof space is properly insulated. Pipes are at risk of bursting and leaking, especially during the winter. Some types of roof insulation will absorb any moisture like a sponge and create a cold, damp environment in your roof space.

The fourth step is to install the insulation. Now, this is the most important step, and if you don't take notice, you are putting your health at risk. Some materials need to be handled very carefully. For example, fibreglass causes skin irritation and can cause extreme itchiness for days or even weeks after handling it. Fibreglass also contains microscopic glass particles that can be inhaled, and it can bury itself into your lungs, causing respiratory problems.

As you can see, it's not just a case of going up into your roof space and rolling out some roof insulation. It has to be carefully thought out. All hazards need to be addressed. If all of this sounds a bit too much for you, I highly recommend you hire a professional to do the work for you.

If you would like a free no obligation quote for a professional insulation specialist to install it for you, I highly recommend you go here .

(They offer some of the best prices online, and it only takes about 45 seconds to complete the quote form)

Insulating a Roof

Here Are Some Of The Most Common Questions I Get Asked About Roof Insulation Costs

What Does It Cost To Insulate A Roof?

The average cost to insulate a roof in the UK is around £500. Keep in mind that this is only an average cost, and the actual cost will vary depending on the size of your roof. Roof insulation costs for large homes will be higher due to the higher cost of materials and labour.

Is It Worth It to Insulate The Roof?

If you are asking yourself this question – is roof insulation worth it, you might be better asking yourself if you want to lower your energy bills? Insulating a roof will help to retain the heat within your home and lower your heating bills during the winter. It is estimated that good quality roof insulation can decrease your heating expenses from anywhere between 10% – 50%. So yes, it's worth it.

What Is The Cheapest Roof Insulation?

The cheapest type of roof insulation is fibreglass (also known as glass wool). Fibreglass roof insulation is the cheapest type of insulation you can buy. Glass wool is the most common type of roof insulation in the UK. Its good insulation value combined with its relatively low-cost makes it a good choice amongst UK households.

Can I Lay New Insulation Over Old Insulation?

You can put new insulation over old insulation if the existing insulation is not wet. If the existing insulation and the new insulation both have a vapour retarder, it can trap moisture in between the two layers of insulation and cause problems in the future. If there is any sign of moisture in the existing roof insulation, it must be replaced before installing the new insulation.

How Much Difference Does Roof Insulation Make?

The purpose of insulation is to help retain heat within your home and reduce your energy bills during the winter.

Home energy experts have calculated that your home can lose as much as 35% of the heat in your home through the roof if it is not insulated properly. But that's not all. You can lose a further 20% through your windows and another 25% through your walls! Properly insulating your home will help to reduce your energy costs and save you money over time.

What Is The Difference Between Insulating A Roof Or A Loft?

Most loft conversions will have had the roof insulated by placing insulation in between the rafters. Insulating a roof for a loft conversion will help to retain heat within the room.

If the roof space has not been converted into another room then you will only need to lay insulation down on top of the joists. The majority of homes in the UK that do not have a loft conversion usually have fibreglass roof insulation laid down on top of the joists because it is the cheapest option to insulate your home.

Are you thinking about a loft conversion? Follow the link to find out how much a loft conversion cost.


If you feel confident enough to do the work yourself, it’s not too difficult to calculate roof insulation cost. Figure out your budget, take measurements and purchase the insulation that fits within your budget.

Make sure you are aware of all the hazards when handling certain types of insulation as its likely to cause skin irritation and possible breathing difficulties.

If you would like a FREE no obligation quote to have fully trained professional insulation specialists to install roof insulation in your home, I highly recommend you head on over to this website.

Take care!

Jim Ardale

(Roof Advisor)