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, an insulating layer is added to the inside walls of your home. 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 easy it is for heat to pass through a material. The lower the U-value of the insulation, the more effective it is at keeping heat inside your home. In terms of cost, you can expect the price to go up as the U-value goes down.

Insulation boards

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.

Dry lining

Wooden frames (called battens) are fixed to the wall. The insulation is fitted inside the frames. Plasterboard is then fitted over the top.

Flexible thermal lining

This is essentially thermal wallpaper. It comes in rolls and is hung in the same way as 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.

Insulated plaster

This is plaster that has insulation mixed into it. It’s often clay or lime-based, and the insulating material is cork. Like other plasters, insulated plaster is mixed with water and then applied 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 will need to be ‘moisture open’. This helps avoid problems with damp as the insulation lets moisture pass through the wall.
It may also be necessary to add 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. Insulation is offered for free, or at a heavily discounted rate.

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

Internal Wall Insulation FAQ

Is internal wall insulation disruptive?

This will depend on what method you use. Flexible Thermal Lining is the least disruptive as it’s essentially just like wallpapering. Any method that involves plastering will mean that some dust is produced. Any method that involves drilling means there will be some noise.
A reputable installer will make sure that all rooms are 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.

Is internal wall insulation expensive?

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

Can I get internal wall insulation if I live in a flat?

Yes. Internal wall insulation is fitted to the inside of your property. This means 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.