Internal Wall Insulation

The best way to improve the energy efficiency of your home’s solid (non-cavity) walls is by adding solid wall insulation. There are two ways to insulate a solid wall:

  • Internal wall insulation.
  • External wall insulation.

With internal wall insulation, installers add insulation to the inside of your exterior walls. So, if external wall insulation is like putting a jacket on your property, internal wall insulation is more like putting on a thick vest.

How to insulate internal walls

There are several options when considering how to insulate an internal wall. Each method varies in terms of cost and effectiveness.

To find out how effective the insulation is likely to be, you can check its U-value. U-values measure how easily heat passes through a material. The lower the U-value of the insulation, the more effectively it keeps heat inside your home. As a result, in terms of cost, you can expect the price to go up as the U-value goes down.

These are rigid boards that come in different materials and thicknesses. It’s a little like fixing large tiles to your walls. Some types of board already have a plasterboard layer attached, so there’s no need to plaster over the top.

External wall insulation fixings secure the insulation in place. The installer fixes the insulation to the wall with a series of battens (frames), an adhesive, or a combination of the two.

This is essentially thermal wallpaper, which you buy in rolls and hang like normal wallpaper. Although it probably won’t keep the heat in as well as other types of insulation, it is something you may be able to install yourself if you’re handy around the home.

This is plaster with insulation mixed in. It’s often clay or lime-based, and the insulating material is cork. As with other plasters, you mix insulated plaster with water and apply it to the walls.

Breathable internal wall insulation

However you choose to insulate your internal walls, it’s important to make sure that the method and materials don’t cause damp or mould issues.

If you’re insulating an historic building, the materials you use should be ‘moisture open’. This helps avoid problems with damp because the insulation lets moisture pass through the wall.

Additionally, you may also need to install extra ventilation so that moisture doesn’t build up indoors.

Internal wall insulation grants

Although generally cheaper than external wall insulation, internal wall insulation can still cost between £5,000 and £12,000.

The Home Energy Scotland Grant offers up to £7,500 of grant funding for internal wall insulation. An optional extra £2,500 is available as an interest-free loan.

To find out more about the Home Energy Scotland Grant, call free on 0808 808 2282 to speak to an energy advisor.

Internal wall insulation is also one of the measures offered through several Energy Efficient Scotland: Area Based Schemes (EES: ABS). EES: ABS use Scottish Government funding to improve the energy efficiency of homes. Since the the government funds these schemes, the internal wall insulation is free, or heavily discounted.

To see if EES: ABS for internal wall insulation is available in your area, contact your local council.

Internal Wall Insulation FAQs

This will depend on what method you use. For example, flexible Thermal Lining is not very disruptive as it’s essentially wallpapering. On the other hand, any method that involves plastering will mean that some dust is produced, whilst any method that involves drilling creates noise. With this in mind, a reputable installer will try to minimise disruption. For example, all rooms should be sheeted up properly to protect them against dust.

How long the install takes depends on the size of the property. A typical timeframe is three to five days.

It is also important to note that certain methods of internal wall insulation will make your rooms smaller by a few centimetres. With dry lining and insulation boards, the walls will protrude a little further into the room. Skirting boards, cupboards and radiators will have to be removed and refitted as part of the process.

Yes. Internal wall insulation is fitted to the inside of your property. As a result,  there’s no need to insulate the whole block as there is with external wall insulation, or all the flats above and below you, as there is with cavity wall insulation.

Again, this will depend on the method used, as well as the size of your property. For example, dry lining or adding insulation boards to a three-bed semi-detached house typically costs around £8,500.

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Home Energy Scotland logo

Changeworks delivers Home Energy Scotland in the south east and Highlands and Islands on behalf of the Scottish Government and Energy Saving Trust.

As well as providing free, impartial expert advice to thousands of people every month to help them to keep warm in their homes for less, they identify funding opportunities for households seeking to install energy efficiency measures.

For more information, give Home Energy Scotland a call on 0808 808 2282 or email and the team will be happy to help you.