In this article

What is roof and loft insulation?

What are the benefits and why is it important?

Is it suitable for my home?

The different options for insulating a roof or loft

The different materials used

The cost of roof and loft insulation

Saving money with roof and loft insulation

Carbon footprint savings

How to install roof and loft insulation

Other ways to insulate the home

Installing insulation in the roof and loft of a home is an easy, cost-effective way to increase energy efficiency and can offer significant annual savings on energy bills. Whether simply rolling it out in the loft space or using it to create a new room or living space entirely.

Roof and loft insulation can reduce annual heating bills, heat loss and cut carbon footprint. Some types can be installed as a DIY project, and with 25% of all heat loss happening through the roof of a home, it's one of the best steps you can take to achieve year-round comfort.

There are some different materials and methods to use, with prices varying slightly depending on how you want to use the loft. In any case, our guide has got you covered, so read on to find out more about the different types, costs, savings and benefits.

What is roof and loft insulation? 

This simply refers to any type of insulation installed in the roof or loft of a home and is likely to be a term you have heard before. Loft insulation is when a layer of material (usually wool) is installed within the loft creating a barrier which prevents heat from escaping during winter and helps to keep the home cool during summer.

The insulation is usually laid between the joists of the roof, which are the beams that lay horizontally across the floor. Insulation is also commonly laid between the rafters, the angled beams that support the roof. Whichever part of the loft you decide to insulate, it can work effectively to retain heat by reducing heat loss.

Where the insulation is placed will have a direct impact on how the loft can be used. If insulating between the joists, this will mean that the living space below is kept warm, but the loft itself will be cold. This is what’s known as a ‘cold loft’, and suitable for storage purposes. If you decide to install insulation in the rafters, it will allow you to keep the home and loft space warm, which opens up the opportunity to use the loft as a spare room or living space.

Installing insulation in the loft has several key benefits including increased energy efficiency, lower heating bills, and could even increase the value of the home. These benefits combined with its relatively cheap cost and ease of install make it a perfect choice for improved comfort.

What are the benefits and why is it important? 

The loft is one of the areas of the home which experiences the highest amount of heat loss. In fact, a quarter of all heat escapes through the roof of the home. So, installing insulation in this area is an impactful way to stop this heat from escaping and to keep you warm during cold weather.

Loft insulation has a long lifespan and helps you to save on energy bills. It is effective for up to 40 years, allowing you to recoup your initial costs and save in the form of reduced annual energy bills year on year. These savings could be as much as £250 annually.1

The environmental benefits are also worth mentioning. Good loft insulation helps reduce a home's carbon footprint and combat climate change. The reduced heat loss in the home will mean that the heating system doesn’t have to run as long, and the home will retain heat for longer, which reduces the amount of fossil fuels needed to keep you warm. A detached home for example, could expect to save just over 1 tonne of carbon dioxide each year. That’s the equivalent of charging a smartphone over 130,000 times.2

Is it suitable for my home?

The good news is that for most types of lofts, insulation is easily installed and can even be installed by yourself as a DIY project with no professional help in most cases. This is unlike other insulation types such as cavity wall insulation which require a professional and specialist equipment.

This ease of install combined with the potential savings on annual energy bills make it a great choice. Before you get started there are some initial things to consider when it comes to deciding whether your loft is suitable. It should be:

  • Easy to access 

  • Have no ongoing damp or mould problems – or problems with leaks 

  • Have joists which are spaced evenly 

  • It should be a non-flat roof 

If your answer to all of the above is yes, it is highly likely that you can insulate your roof or loft. If, however, you think any of the above may be a current issue in the home, you should first consult a professional installer for a consultation and assessment of the loft space. 

Flat roofs should always be insulated by a professional and any issues with damp, mould or leaks should always be addressed prior to install. Without doing this, you risk damaging your brand-new insulation, making it ineffective.  

If you’re thinking of converting the loft into a spare room or living space, this will require professional installation as well. 

The different options for insulating a roof or loft 

Depending on how you want to use the loft, there are some different insulation methods that can be chosen from: 

Cold loft 

A cold loft is a common layout in many homes. To create a cold loft, you will need to lay the insulation over the joists on the floor of the loft. This keeps the home warm but means the loft space itself will be either cold or hot, depending on the season.  

A cold loft is a relatively easy task to install as a DIY project and is slightly cheaper than other types, but still delivers annual energy bill savings. The loft can be used for storage but does require the floor level to be raised. 

Warm loft  

A warm loft is perfect for storage, and to keep both the home and loft space warm in winter and cool in summer. Creating a warm loft involves insulating between the rafters under the roof itself. This is an ideal set up if you have a loft conversion, or items in storage that are sensitive to temperature. The downside to this is that they are a much more complicated job, more expensive, and it’s highly recommended to consult a professional for installation.  

Room in roof 

Room in roof insulation is ideal if you want to use the loft as a living space or spare bedroom. You need to make sure that all the walls and ceilings between the loft / room and the unheated space are insulated. Room in roof is when insulation is installed between the rafters, and existing plaster walls, which will be installed as part of the conversion to a room. As with warm loft insulation, this will need to be done by a professional.  

Flat roofs 

Flat roofs are usually insulated from above and require a professional to carry out the work. A layer of insulation board is added on top of the existing roof surface, with a new weatherproof layer added on top of this. Alternatively, the insulation can be placed between the joists inside the loft, which is often the cheaper option. 

The different materials used 

There are many different options for the material that can be used when insulating a roof or loft, the most common ones are these: 

  • Matting 

  • Loose-fill 

  • Rigid insulation boards 

  • Blown insulation  

We cover these in much more detail in our general home insulation guide.

The cost of roof and loft insulation 

The good news is that roof or loft insulation is one of the most affordable types of insulation for the home. Some types of roof or loft insulation can be done yourself as a DIY project and come with some good annual savings on energy bills. Professional installers can do the job but this will increase the price when factoring in callout and labour costs.  

As with all types of insulation, the size of the home and loft space to be insulated will determine how much it costs. For an installation of 0–270mm mineral wool loft insulation you can expect to pay this depending on the type of home:3

  • Detached: £395 

  • Semi-detached: £300 

  • Mid-terrace: £285 

  • Detached bungalow: £375 

Graph showing the costs of roof and loft insulation by home type

Just two years to earn back your install costs 

To show how cost-effective roof and loft insulation can be, we’re going to look at an example of a detached home, which will on average come at a cost of £395. The annual savings on energy bills can be up to £250 per year, meaning you earn back the install costs in less than two years and can continue to make savings year on year. 

Government grants

Some government heating and home improvement grants are still available to offer financial support for insulation installs. While the Green Homes Grant is no longer available, it is worth checking out the Energy Company Obligation, which is a means tested scheme designed to offer support with install costs.  

Saving money with roof and loft insulation 

As well as being cost effective to install, roof and loft insulation will help you to reduce annual energy bills resulting from having a much more energy efficient home. As you’ve seen above, you can typically expect to earn your install costs back within 2 years, even for the largest detached homes. The typical annual savings you can expect for 0mm–270mm mineral wool insulation are:4

  • Detached: £250 

  • Semi-detached: £150 

  • Mid-terrace: £135 

  • Detached: £210 

Annual energy bill savings for roof and loft insulation, by house type

If opting for a professional installation, you could consider having this work done at the same time as other home improvement work, which can reduce labour and callout costs. If you’re interested in an air source heat pump or hybrid heating, having good home insulation is a must. If you have access to your home’s Energy Performance Certificate (EPC), then it is worth taking a look at this for any insulation recommendations, which may single out the roof and loft.  

Carbon footprint savings

As well as being great for your wallet, insulating the roof or loft is a great way to reduce carbon footprint and fight climate change with the increase in energy efficiency for a home being great for the environment.  

As a result of improving a home's insulation, more heat is retained in the home. The amount of carbon emissions produced by the heating system are therefore reduced since the system doesn’t need to work as hard to achieve a comfortable temperature. You can see below just how much carbon emission savings can be made:5

  • Detached: 1 tonne (CO2/year)  

  • Semi-detached: 610kg (CO2/year) 

  • Mid-terrace: 550kg (CO2/year) 

  • Detached: 860kg (CO2/year) 

Carbon emission savings of roof and loft insulation by house type

To help put these carbon emissions savings into perspective, 1 tonne of CO2 that can be saved per year for a detached home is the equivalent of 42 bags of waste being recycled instead of being sent to a landfill.6

How to install roof and loft insulation 

If your loft is suitable for insulation, the good news is that, for a basic ‘cold loft’, you can go ahead and tackle it as a DIY project. It’s a simple enough job and helps keep costs down. 

So long as you have a dry attic with evenly spaced joists (as mentioned earlier), the easiest route to take is to insulate between these joists using rolls of blanket insulation typically made from wool, glass fibre or other recycled materials. The minimum recommended depth of this insulation material should be 270mm across two layers of insulation.  

How to install: 

  1. Make sure the loft is tidy and clear of any boxes or debris, with clear access and visibility of the joists. Check for any light fittings coming through into the loft space, these will need to be capped prior to install.   

  2. Make sure to wrap any exposed pipes with foam lagging and to wrap the cold-water storage tank in a tank jacket. When the loft is insulated using the joists it can mean it gets very cold in the loft space itself, so this step is to prevent pipes from freezing. Foam lagging can be purchased at most DIY stores for a low price. 

  3. Measure the loft space and depth of the joists to ensure you buy enough of the correct insulation material to fill in between all the joists. You should measure the distance between the joists and buy a roll of insulation as close to the width measured as possible. The recommended depth for the first layer of insulation should be 100mm and the material you will typically buy will be made from glass fibre or wool. The roll of material may need to be cut to size, but this can be done with a simple utility knife. Your place of purchase for the material should be able to help with any questions and we would always recommend home delivery due to the size of the rolls.  

  4. Unroll your material and lay it between the joists lightly pressing it to fit it snugly between each joist. Once this first layer is rolled, the insulation should match the height of the joist. Your earlier measurements should ensure this is a snug fit.  

  5. Create a second layer which will typically be 200mm thick at a 90-degree angle to the first layer. Start at the furthest point from the centre of the loft.  

  6. Insulate the loft hatch as the final step to complete the insulation, this will ensure that no draughts or cold air escapes into the home through the hatch. You can do this by simply stapling some of the insulation material on top of the hatch.  

That's it! How to simply insulate your loft in a ‘cold loft’ setup. As you can see, it only takes a few simple steps to improve the energy efficiency of the home and to reduce heat loss. Once the insulation is installed, you will immediately benefit from energy bills savings and increased comfort.  

If you’re looking to insulate a flat roof, create a warm loft, or create a room in roof set up, then we would always advise consulting a professional. The installation for these types of setups is more complicated and does require specialist knowledge and equipment.  

How to find an installer:

In the event that you’d like to choose one of the more complicated types of loft insulation or you’d just like the peace of mind of everything being taken care of for you, you can consult one of the many professional installers. Not all installers are created equal, however, so you may want to check out the National Insulation Association (NIA) website to find an installer in your area

All installers registered with the NIA must abide by a strict code of practice to ensure all installs are carried out to the highest standard. 

Other ways to insulate the home 

Besides the roof and loft, there are some other choices that can be made to insulate the home. We’ve complied a complete list of measures in our guide to home insulation, some of which we’ve listed below. 

Solid wall insulation  

If solid walls are installed in the home, they too can be insulated. Solid walls contribute to 45% of overall heat loss in the home, so insulating them can be a great way to reduce heat loss. Typical energy bill savings can be up to £375 for a detached home, so it’s a worthwhile investment. 

Cavity wall insulation

If you have a home built after 1920, it is highly likely that you’ll have a cavity wall construction. This is the construction of an inner and outer wall of the home, with a small space in the middle known as the cavity. This cavity can be filled with insulation to reduce heat loss and in doing so you could save up to £305 per year on annual energy bills. 

Draught proofing

Draught proofing is another affordable option to reduce heat loss and increase comfort in the home. Measures to reduce draughts can include sealing skirting boards and gaps in windows and doors. You can typically save around £20 per year by increasing draught proofing in the home.  

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