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Solid wall insulation guide

Our guide will take you through the benefits of solid wall insulation and answers the top questions customers have about this type of insulation.

What is solid wall insulation?

Most homes built before the 1920s were built with solid walls. Later on, cavity walls were used to build homes as they were seen as a way to tackle damp issues.

Solid wall insulation involves attaching a layer of insulating material to either side of a solid wall, which means it can be installed inside or outside your home.

Wondering what the difference is between a solid wall and a cavity wall?

  • Solid walls have no gaps and can be made up of many combinations of materials. They're generally considered bare brick or stone or come with a plastered finish
  • Cavity walls are made of two layers with a gap or ‘cavity’ between them

What are the different types of solid wall insulation

installing external wall insulation

External wall insulation

External wall insulation refers to the installation of insulation material onto an existing exterior wall. This insulation layer is then protected from weather elements by either a coat of render or an alternative cladding.

Internal wall insulation

Insulating internal walls involves installing insulation on the inside walls of your home to create a thermal barrier that minimizes heat loss and improves energy efficiency. This is particularly effective for solid wall properties.

How can I tell if I have solid walls?

Solid walls come in many different forms. Here are some common ways to tell if your home has solid walls:

  • It was built before 1920

  • The walls are less than 260mm thick

You might need planning permission before installing solid wall insulation — check with your local council before starting.

Top questions customers ask about solid wall insulation

Is it worth insulating solid walls?

The short answer is yes. Any improvements to insulating your home will make your home cosier and more efficient, which means you could also save money on your energy bills. Cavity wall insulation is typically less expensive than solid wall insulation. However, investing in solid wall insulation could result in significant long-term savings.

The graph below shows the typical annual savings on your energy bill (£/year) based on insulating a gas-heated home.  

Estimates based on insulating a gas-heated home. Costs may vary significantly depending on the level of work required. Estimates are based on a typical installation, ranging from a small flat to a large detached home. Figures for England, Scotland and Wales are based on fuel prices as of July 2023.

How much does solid wall insulation cost?

Typical installation costs of solid wall insulation can vary as follows:

  • External wall insulation: around £11,000
  • Internal wall insulation: around £7,500
    Based on a typical 3-bedroom, semi-detached house in Great Britain

The price you pay for this work will depend on the condition of your walls, the size of your property and your installer.

How can I make a saving on installing solid wall insulation?

A way to make a saving on this is to bundle in its work with other home improvements rather than doing the whole house at once.

If you're planning to redecorate or install a new kitchen or bathroom, you can also consider adding internal solid wall insulation to the project. This can help you break down the costs and tackle one room at a time. Additionally, you can save on scaffolding costs by incorporating external wall insulation into other projects, such as getting a new roof or installing solar PV panels. It's also worth getting a quote for a complete overhaul, including external solid wall insulation, as part of any damp proofing or re-pointing work.

Can I get solid wall insulation through EDF?

Unfortunately at the moment, we don't offer solid wall insulation. However, if you qualify for ECO4 and live in a home where the EPC rating is E or below and you're receiving specific benefits, solid wall insulation may be recommended as part of a package of improvements to make your home more efficient and increase your EPC rating.

Insulation products we offer

thermal loft insulation roll

Loft insulation

from £789 professionally installed

Around 25% of your heating can be lost into through your roof - save up to £475 a year on energy bills

Cavity wall insulation - Installing cavity wall insulation

Cavity wall insulation

from £723 professionally installed

You could be losing 33% of heat through your walls - save up to £520 a year on heating bills

Insulation and energy-saving advice

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Understanding your home's Energy Performance Certificate (EPC) can help when deciding what energy-efficient improvements to make. In addition, it can also highlight effective low carbon alternatives and their associated cost savings and benefits.

floor insulation under concrete

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partially insulated house showing heat loss

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