How to insulate your home

Many of the homes in the UK are poorly insulated and inefficient to heat, leading to high energy bills and a big carbon footprint.

The most obvious reason to improve your home's efficiency is for an immediate decrease in your energy bills. However, the benefits of insulation should not be measured in cost savings alone. 

Good insulation also improves comfort levels by keeping you cosy in winter and cool in summer, and cuts your home’s carbon emissions by lowering your energy consumption. 

It can also help futureproof your home. Insulation will reduce the need for fans or air conditioning and help avoid overheating during more frequent summer heatwaves. 

Better insulation prepares homes for the switch to technologies such as heat pumps and other low carbon heating systems, which work most efficiently in well-insulated buildings. 

With energy bills predicted to remain higher than before the energy crisis for the foreseeable future, and government grant money available for some households, there’s never been a better time to insulate your home.

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Find out how energy efficient your home is

The first step is to find out how well insulated your home is already, and how to improve it most cost effectively. 

If your home has an Energy Performance Certificate, it will help you identify possible improvements. Your property is likely to have an EPC if it has been marketed for sale or rent since 2008.

Find your EPC

You can find any current or expired EPC for a home in England, Wales, or Northern Ireland on the government’s EPC Register or, in Scotland, on the Scottish EPC Register run by the Energy Saving Trust. 

You can also find a list of qualified Domestic Energy Assessors on either website.

EPCs are valid for ten years, so yours may have expired. If you have made changes to your home since the date of the EPC assessment, it may no longer be accurate.

If your home doesn’t have an up-to-date EPC, you can get one for around £60-£120, depending on the size and location of your home. 

For a more detailed report, look for assessors who offer a home energy audit. Although more expensive, it may include thermal imaging as well as one-to-one advice and a comprehensive plan to help you upgrade your home.

EPC ratings explained

The EPC shows the current and potential energy efficiency rating of your home from A (most efficient) to G (least efficient). It also lists ways you can improve the rating along with indicative costs. 

There is a government tool to find ways to save energy in your home with more information about what you can learn from your EPC. It also has a phone line (0800 098 7950, open Monday to Friday, 8am to 6pm and Saturday 9am to 12pm) where you can get advice on retrofitting your home.

Recommendations may include big projects like installing external wall insulation or solar panels, as well as smaller changes such as switching to low-energy lighting. 

The EPC lists the recommendations in the order that they should be carried out to maximise their effectiveness.

Home energy audit checklist

If you don't have an EPC, or other professional assessment, you can try doing a basic DIY home energy audit. Walk round each room in turn and note down what you find.

• Insulation: Inspect the loft, external walls and ground floor, if accessible. Look for insulation around the hot water tank and pipes.
• Draught proofing: Check around doors, windows and other openings for draughts and gaps. Don't forget the loft hatch, letter box and keyholes.
• Heating: Make sure your boiler, radiators or other heat sources are working efficiently, and check that heating controls, timers and thermostats are set correctly. 
• Lighting: Check that all lighting is fitted with efficient LED bulbs, including in ovens, extractor hoods, and external lights. 

Armed with your energy efficiency information, you can start planning what action to take.

Cutting energy use: the 'fabric first' principle

The warmth created by your heating system – and the energy used – will be quickly lost through any uninsulated areas. Tackling these first will make your home noticeably warmer, lower your bills and improve your EPC score. 

Making improvements to the external envelope, or fabric, of your home is widely acknowledged to be the best place to start if you are trying to reduce your energy use.

There are three main elements of your home that will benefit from insulation. These will prevent the most heat loss and make the biggest savings on your energy bills

Insulate the walls

Uninsulated homes lose more than a third of their heat through the external walls. A detached house loses heat through the walls on every side, as they are all exposed to the outside air, whereas a mid-terraced house or flat has fewer external walls so experiences less heat loss. 

Check what type of walls you have. You need to know how your walls are built because the methods of insulating each type are quite different. The age of your home can give you an idea of the type of wall construction.

• Most homes more than 100 years old have solid walls, usually brick or stone. Internal and external solid wall insulation systems are available.
• Homes built after 1920 are likely to have cavity walls, comprised of two walls with an air gap (the cavity) in between. Insulation can usually be installed in cavities no less than 50mm wide.
• Modern homes built after 1990 normally have insulated cavity walls, and shouldn't need to be upgraded.

Read more about solid wall insulation cost and savings and cavity wall insulation installation, including costs and savings.

If your home has a steel or timber frame, or is a pre-fabricated concrete construction, you'll need advice from a specialist insulation installer or retrofit coordinator.

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Insulate the floors

Up to 15% of lost heat goes through the ground floor of your home, so it should be insulated if possible. It's not normally needed for upper floors, but if you have a room above an unheated space, such as a garage, insulation may be beneficial.

Check what type of floors you have. Like walls, you need to know what type of floors you have to choose the right sort of insulation.

• Suspended floors, usually floorboards, rest on joists above a void space. They can be insulated using rigid boards, mineral wool, or spray foam insulation.
• Solid floors are generally stone or concrete. A layer of rigid insulation can be laid on top.

Many homes have both types of floor so you may need more than one approach. 

Find out more about floor insulation options and costs.

Insulate the roof or loft

Insulating a roof or loft is one of the most cost-effective ways to improve your home's energy efficiency. Large, detached houses and bungalows lose a high proportion of their heat through the roof, but most homes can benefit from a minimum of 270mm of loft insulation. 

What type of roof do you have? Most roofs can be insulated, but there are different methods.

• Pitched roofs can be insulated at joist level as a cold roof, often called loft insulation, or at rafter level as a warm roof. Insulation rolls, rigid boards, and spray foam applications are all available.
• Flat roofs can be insulated as a warm deck, cold deck, or inverted roof.

Learn more about roof insulation types and the costs of loft insulation.

More ways to keep the heat in

As well as insulating the external envelope, there are other good ways to improve your home's energy efficiency and prevent heat from leaking out.

• Upgrade windows and doors, especially if you have single glazing. Find out how to choose the best type of double-glazed windows and doors for your home
• Insulate the hot water tank and pipes. Cylinder jackets and foam pipe insulation are cheap to buy and easy to fit. Insulating your hot water tank alone is likely to pay for itself in just one year and is very easy to do.
• Add reflective panels behind radiators to prevent heat from being lost through external walls. They are especially effective for radiators on uninsulated solid walls.
• Draught proof around windows and doors, keyholes, and letterboxes using low-cost, off-the-shelf products. Read more about how to draught proof your home.

How to heat a well-insulated home

A well-insulated home will have a lower heat demand than a poorly insulated one. When you replace or upgrade your heating system, it should be sized to suit the reduced level of heat demand. 

A system with a lower heat output is likely to be cheaper to buy and install and the ongoing running costs – your energy bills – will also be lower. 

A good heating engineer should be able to calculate the right size boiler to meet your hot water and heating needs.

Check Which? Trusted Traders to find your local heating engineers.

Energy-efficient fossil-fuel heating

Although gas and oil boilers will be phased out in due course, they may still be the best choice for you right now. To keep carbon emissions as low as possible, find out which boilers are the most efficient and find out how to use heating controls and thermostats most effectively.

Switching to a low-carbon system

A whole new heating system isn't possible for everyone, so it's worth working through the points above this one before you consider an upgrade. 

But if your home is very well insulated, and if you're in a position to do so, it's time to think about the way it is heated.

Over the coming decade or so, new types of heating system are likely to become available. Alongside ground and air source heat pumps, we can expect to see other technologies that use electricity to generate heat. 

This is an increasingly low-carbon energy source as more electricity is generated by renewable sources like wind and solar. 

Read our overview of the different types of heating system currently available to find the best heating for your home.