How to insulate a house to save money and energy

Beyond simply making your home more comfortable on cold and hot days, effective insulation can dramatically reduce your energy consumption, which not only leads to a lower carbon footprint, but also lower bills.

In this guide, we’ll explore all of the main ways you can insulate your home to make a lasting, positive impact on your energy bills.

What is home insulation?

Home insulation is the process of stopping the transfer of heat between the inside and outside of your property. In the winter, a well-insulated home will keep the warmth generated by your heating system trapped indoors while stopping it from escaping, and stopping the cold air from coming in and undoing your system’s hard work.

At the same time, the same insulation will also keep hot outside air from creeping into your home, and keep the cool air inside.

Without proper insulation, a significant amount of a home’s heat can be lost in the winter, making it difficult to maintain comfortable indoor temperatures. And although it’s to a lesser extent, similar can be said for summer – air conditioners can be expensive to run, and have to work harder to cool a home where hot air is constantly flowing in.

What are the benefits of home insulation?

Reducing your energy use, energy bills and carbon footprint are all great reasons to make sure you have optimal home insulation. But the benefits don’t stop there – good insulation also provides:

• Noise reduction – Many insulation materials also have sound-dampening properties, which can help to reduce noise transmission from outside your home and between different rooms inside your home.

• Condensation control – By maintaining a more stable internal temperature and reducing cold surfaces where moisture can condense and collect, good insulation can also help prevent damp and mould.

• Better air quality – Good insulation doesn’t just keep unwanted hot or cold air from getting in: it also helps to prevent pollutants and allergens like pollen from getting into your home, too.

• Increased property value – An energy-efficient home with a good Energy Performance Certificate (EPC) rating, which is often improved by good insulation, can add significant value to your property. Check out our EPC guide to find out more about Energy Performance Certificates.

What types of home insulation are there?

• Walls – Walls can account for the largest amount of heat lost from a home, standing at a 35% loss. The type of insulation available depends on the type of wall: solid walls are usually found in properties built before the 1920s, while cavity walls are often found in properties built after. For solid walls, insulation boards can be attached to the insides and outsides of the walls. Cavity walls can be filled with insulation material by injecting it through small holes drilled into the walls.

• Roofs and lofts – Because heat rises, roofs and lofts account for the next largest amount of heat loss in the home, at 25% loss. Insulation, spray foam and foil can be used to insulate roofs, while blanket and loose-fill insulation can be installed in lofts.

• Windows and doors – Even when closed, heat can escape through draughty gaps, accounting for about 10% of heat loss in the home. Blocking gaps and hanging heavy curtains in winter can go a long way in keeping the cold air out.

• Floors – Although heat rises, some heat can also be lost through the floor, particularly if you’re on the ground floor – which is also at around 10%. Foam insulation and thick carpets can be laid down to reduce this kind of heat loss.

• Pipes and water tanks – Hot and cold water pipes can be insulated with tube insulation to prevent heat loss and condensation, while an insulating jacket can be installed on water tanks.

What materials are insulation made of?

• Fibreglass – Also known as glass wool, fibreglass is made from fine strands of glass, and is often available as blanket insulation and loose fill for roofs and lofts.

• Mineral wool – An alternative to fibreglass, mineral wool is made of rock minerals (which is why it’s also sometimes known as rock wool). It’s sometimes considered to perform better than fibreglass, but it’s often more expensive and more difficult to work with because it’s denser.

• Sheep’s wool – A natural alternative to mineral wool and fibreglass, sheep’s wool can be pricier but more versatile, and can be used to insulate roofs, lofts, walls and floors.

• Cellulose – Made from plant fibres, cellulose is often used to insulate cavity walls, floors and in loft spaces.

• Foam boards/rigid foam insulation – These are solid boards made from plastic foams, and can be used to insulate external and internal solid walls, floors and roofs.

• Spray foam – This is a liquid foam that expands when sprayed and then hardens when drying, and is used to fill hard-to-reach spaces to create an airtight seal, for example, in roof eaves and wall cavities.

• Loose fill – Often made from fibreglass, mineral wool or cellulose, loose fill is quick to install by blowing it into crevices and is often used in lofts.

How much money can insulation save me?

Good home insulation can save you a substantial amount of money, but it varies based on your property type, existing insulation levels and energy consumption habits.

According to the Energy Saving Trust, UK households can save hundreds of pounds through proper insulation. For example, typical annual savings from insulation for a three-bedroom semi-detached home in England, Scotland and Wales could be:

• Roof and loft insulation: £230

• Cavity wall insulation: £240

• Solid wall insulation (internal and external): £320

• Floor insulation: £70

How much does insulation cost?

Similarly to the amount you can save, the cost of home insulation can also vary significantly depending on the type, material, size of the area and complexity of installation. Here are some estimated costs for a typical semi-detached, three-bedroom UK home according to Energy Saving Trust:

• Roof and loft insulation: £900

• Cavity wall insulation: £2,700

• Solid wall insulation (internal): £7,500

• Solid wall insulation (external): £11,000

• Floor insulation: £4,700

While upfront costs can seem high, especially for solid wall insulation, the long-term savings on energy bills often result in a relatively quick payback period.

You can also start with cheaper insulation solutions like draught-proofing your home. Getting your whole home professionally draught-proofed can cost around £250 in total, but quick, temporary DIY fixes can be more cost-effective. For example, you can use an old piece of clothing to block a gap under a door, or stick a draught seal strip around your windows.

Which areas of a house are best to insulate?

To maximise both your savings and your comfort, it’s best to prioritise insulation in the areas where the most heat is lost.

1. Walls - These are the biggest culprit of heat loss in the home, whether you have cavity or solid walls. They can lose up to a third of your heat, so making sure your walls are properly insulated should be high on your list.

2. Roofs and lofts – Although they’re the next major culprit of heat loss after walls, roofs and lofts can actually be the cheapest area of the home to insulate.

3. Floors -- Insulating suspended timber floors or concrete floors can significantly reduce cold spots and improve warmth.

4. Draughts -- blocking unwanted gaps around windows, doors and other openings like keyholes and letterboxes can be a low-cost but highly effective way to prevent heat loss.

5. Pipes and water tanks – Insulating hot water pipes and your hot water cylinder helps to retain heat, reducing the energy needed to heat water and ensuring it stays hot for longer.

What government grants are available for home insulation?

The UK government promotes energy efficiency improvements, including insulation, through various schemes designed to help homeowners and tenants reduce their energy bills and carbon emissions. These grants are often targeted at low-income households or properties with low energy efficiency ratings.

Here are some examples of government schemes:

• The Great British Insulation Scheme (GBIS) – Launched in 2023 (then called ‘ECO+’) and running until 31 March 2026, this scheme aims to help the least energy-efficient households in England, Scotland, and Wales with the cost of installing new home insulation.

• Energy Company Obligation (ECO4) – This ongoing scheme places a responsibility on large energy suppliers to deliver energy efficiency measures to eligible households. If you or a member of your household received certain income-related benefits, you may be eligible for free or heavily subsidised insulation measures. This scheme is also open until 31 March 2026.

• Warm Homes: Local Grant – Part of the government’s Warm Homes Plan, this grant aims to increase low-carbon heating installations in low-income homes. The scheme opened in April 2025.

Before you apply, it’s crucial to check your eligibility for these schemes through the government’s portals or by contacting your energy supplier.