Insulation Facts

Loft insulation is a layer (or layers) of material with thermal properties which reduces the amount of heat lost from your home. It essentially acts as a shield against the cold outside world. It traps the heat in air pockets to prevent it from escaping. The recommended 270mm of loft insulation keeps the heat in your home.

Mineral wool is made from a selection of raw materials, such as stone and glass. They are heated to a high temperature and spun into a light fibre structure.

Fibreglass is made in a similar way but it uses recycled glass. The glass is heated and then, once melted, is spun to create fibres. It is also sometimes called glass mineral wool.

You can also get insulation made from natural products, such as sheep’s wool or thermos-hemp. They do not contain irritants so are easier to work with, but are more expensive.

From any local DIY store or online. They come in rolls with various depths to suit your needs. There are also loft insulation boards but these are more expensive.

If installed correctly and in the right conditions (no damp issues, for example), you can expect loft insulation to last around 40 years.

Lots of homes have some loft insulation but, in some properties, it may not be adequate, especially if your loft insulation was fitted some time ago. The recommended depth is 270mm. You can retain more heat in your home by laying extra insulation on top of, and at a 90 degree angle to, whatever is already in place. This is called top-up or cross laid insulation.

If you already have 270mm of loft insulation correctly fitted, whatever the material, then there is no need to top this-up any further. Have a look at One Home’s guide for other energy saving measures around your house.

A guarantee provides an extra layer of protection if you are having insulation professionally installed. We recommend finding installers through TrustMark as all works carried out come with a minimum two year guarantee. Installers who are members of The Insulation Assurance Authority (IAA) can also offer guarantees covering different types of energy efficiency insulation measures and will cover you for any failures in workmanship and materials.

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That depends on a variety of factors, such as the type of house you have and whether you choose to do the work yourself. Use our guide to find out cost savings and pay back periods according to your individual circumstances.

We are living through turbulent times, politically and economically, and this has played into the rising energy prices. This has been coupled with an historic over-reliance on fossil fuels which has meant the energy system in this country is not able to absorb these global shocks. As the pandemic lockdowns were lifted, industry, along with other sectors, required more energy which put pressure on suppliers. Russia’s invasion of Ukraine led to cuts in gas supplies to Europe which sent prices soaring. While prices in the UK have stabilised somewhat, energy costs are still significantly higher than they were two years ago. Prices are likely to remain at well above pre-pandemic levels and are forecast to continue as such for the rest of the decade.

This is possible as it will likely increase your Energy Performance Certificate (EPC) rating. An EPC gives a property an energy efficiency rating from A (most efficient) to G (least efficient). You can check yours here. Your EPC will identify recommended energy efficiency measures, such as loft insulation, to achieve a better rating. Research from Knight Frank in 2022 shows that homes moving from band D to band C added three per cent to their value over and above local house price growth (equivalent to £9,003 based on the average resale value).

Funding and grants

For some people, there are grants available. There are two Government schemes available –  the Energy Company Obligation (ECO) scheme and the Great British Insulation Scheme. However, for both, you need to be eligible. For the ECO scheme, you have to own your home and receive certain benefits. See the full list here.

The Great British Insulation Scheme is essentially an expanded version of ECO. To be eligible for funding, you need to own your home, live in a home with a low-rated Energy Performance Certificate (EPC) and live in a certain council tax band (A-D in England, A-E in Scotland and Wales). You need to contact participating energy suppliers for more information.

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Using your loft after installation

Laying insulation rolls on the floor of your loft is by far the simplest and cheapest option. For this reason, the majority of homes have insulation on the floor of their attic with the first layer lying between the joists (the beams that run across the roof). If you want to keep the loft as a useable space in the future, such as a study, you will want to insulate in between and on the roof rafters. This is more complicated and therefore more expensive. You will also probably need a qualified installer to do this.

You can either fit floor insulation board which has the insulation built in or you can use standard insulation rolls and fit plasterboard or chipboard on top. It’s important that you don’t compress the insulation, so you can buy ‘loft stilts’ which fit onto the joists. These allow you to preserve the depth of the insulation while ensuring the loft can still be used for storage.

Yes, you can certainly lay an additional layer of insulation over the boards. Leave a gap around the eaves so that there is enough ventilation in the loft space to prevent problems with damp, mould and condensation. This rule on ventilation applies to all installations of insulation.


If you can safely access your loft space, then checking if you have loft insulation and its depth should be easy. Loft insulation is usually fitted between and across the wooden joists. From the location of the loft access point, you can either use a ruler or tape measure to measure the depth of what is currently in place. Lofts can get dusty so remember to wear appropriate clothing and gloves. Alternatively, you can contact a reputable loft insulation installer who will carry out an assessment.

For the majority of people, mineral wool or fibreglass are great options. Mineral wool is heavier, denser and more rigid which means it has slightly better thermal properties. Fibreglass has more flexibility so it’s a good option if you have obstructions or curved walls to accommodate, and it is cheaper. 

You can also get floor insulation board which means you can insulate at the same time as boarding your loft. However, it is a more expensive option.  

If you wish to insulate with natural materials, sheep’s wool is an option. It is flexible and easy to cut and fit. However, its thermal properties are not as good as manmade materials and it is also more expensive. Bear in mind that you need to buy wool that has been treated with chemicals to ensure it is insect resistant. 

Spray foam is not accepted by many mortgage companies so it is best avoided for insulating lofts.

You will need an insulation cutter, good scissors and protective clothing. Overalls that cover your clothes, gloves, a mask and some goggles are recommended. You will not need protective clothing if you are using sheep wool. If the loft space is not well lit, you will need to think about how you light the space while carrying out the work. You will also need a sturdy ladder if you don’t have built-in loft access. 

The laying out of the insulation should take no more than a weekend depending on the size and access in your attic. You will need to factor in some time to clear the loft, if that is needed.

Extra insulation means the loft area will be cooler as heat will be trapped in the rooms below. Water vapour in the loft area can settle on cold surfaces, which can cause condensation or mould. If you’re installing loft insulation yourself, be careful not to cover any air vents, grilles or air bricks, and leave an air gap of at least 5cm between the face of the insulation and the edge of the roof. If you have any concerns about your loft, seek professional advice on how to tackle this before installing insulation.

Yes. The loft space will be a lot cooler once you have installed insulation. Cold water pipes and tanks may freeze. This is easily tackled by fitting pipe insulation which you simply cut and fit around exposed pipes. Cold water tanks can be fitted with an insulated tank jacket of the appropriate size. Insulation should not go under the water tank.

Most importantly, remember to kneel or stand on the joists only (the beams that run across the roof) or use a crawl board that can span across the timber joists. Do not walk in between joists if your roof isn’t boarded as there is a risk your foot will go through the ceiling below. Remember to wear appropriate protective clothing.

Professional installation

Go to the TrustMark website where you can find local tradespeople who are registered to do this work. TrustMark is the only Government endorsed quality scheme for work carried out around your home. Tradespeople who have signed up to the scheme have committed to maintaining a framework of standards, covering technical competence, customer service and trading practices.  

The TrustMark Home Improvements app has been created for homeowners who want to repair, maintain, or have renovations made to their property. The app will help take you through things to think about when making home improvements.

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This information is provided for guidance only. Please see the full disclaimer in our terms and conditions.

DIY cost estimates include VAT. Professional installer estimates exclude VAT as this is not applied to insulation services.