How to buy wall insulation Solid wall insulation

Solid wall insulation could save you around £445-£475 a year on your energy bills

You could save around £445-£480 a year on your heating bills by installing solid wall insulation.

According to the National Insulation Association (NIA), about a third of UK homes have solid walls. The NIA estimates that 45% of heat from these homes could be escaping through walls.

Solid wall insulation costs and savings

Internal solid wall insulation costs around £42 per m² of wall, according to the NIA.

The price of external insulation varies depending on the size of your property, the condition of its walls and whether other building work or repairs will be taking place at the same time. As a general guide, you should expect to pay between £5,500 and £8,500 for internal solid wall insulation and between £9,400 and £13,000 for external solid wall insulation.

While solid wall insulation is more expensive than cavity wall insulation, you should see bigger savings on your heating bills.

The table below shows you can reduce your heating bills and CO2 emissions by insulating your solid walls.

Figures based on a typical gas-heated semi-detached three-bedroom house. Source: the Energy Saving Trust.

Internal or external wall insulation?

Solid walls can be insulated either internally or externally. Both options will reduce heat lost from solid walls, so the decision is usually based on factors such as:

• your budget
• ease of access
• aesthetic considerations
• the severity of heat loss from your property
• whether your home requires other repair work to interior or external walls.

Solid wall insulation is fixed to external or internal walls

External solid wall insulation

External insulation involves fixing an insulating material to external walls with a protective render or decorative cladding over the top.

The thickness of the insulation needs to be between 50mm and 100mm. It's usually installed when a building has severe heating problems or already requires some form of repair work that provides the opportunity to add insulation.

External insulation is generally more expensive than the internal type. However, it's usually the most suitable option as the installation process does not disrupt the internal design and decoration of a home.

Decorative coatings can be used to improve the appearance of the outside of your home. External insulation can also match a wide variety of home designs, such as Georgian, Victorian and Edwardian-style properties.

Internal solid wall insulation

Internal solid wall insulation usually involves fitting ready-made rolls or boards of insulating material over the inside walls of your house. This can be disruptive – you’ll need to relocate plug sockets, radiators and fitted furniture.

Your walls will need to be carefully prepared before internal insulation can be fitted. Any damaged plaster needs to be either repaired or removed, and bare brickwork should be treated to eliminate areas where air can escape. You’ll also experience a slight reduction in floor space due to the extra thickness of insulated walls. 

However, this option is usually cheaper than external solid wall insulation and can be installed on a rolling, room-by-room basis.

Solid wall insulation is more expensive than cavity wall insulation

Paying for solid wall insulation

Financial help from the government or your local council may be available for insulation if you're planning to make energy-saving improvements to your home. See our guide to energy grants for more details.

The Energy Saving Trust also has an online search tool for grants and offers that may be available to you.

You can find out more information about solid wall insulation, including how to find an installer, from the NIA and the Insulated Render and Cladding Association websites.

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