What’s the best type of internal wall insulation?

Internal wall insulation can be an option if you have solid walls, don’t feel cavity wall insulation is enough or you don’t have the budget for external wall insulation. As 35% of heat is lost through the walls of a property, anything you can do to reduce this means a more constant temperature and lower energy bills.

It can have some downsides – insulation can encourage damp and mould if not installed correctly and adding to walls encroaches on room space – but if done properly it can be an effective way to insulate.

There are a number of options as to which insulating material you go for – it depends on the condition of your walls, the space available, and the budget.

Before you choose the type of insulation, you need to decide how it will be fixed to the wall. There are two options:


If the plaster is in good condition and there is definitely no damp, insulation can be fixed directly to the wall. Boards can be made of:

  • rigid foam (cheap, light, comes with waterproof coating to prevent damp)
  • mineral wool (good insulating and soundproofing qualities, moisture and fire resistant)

Install a stud wall

Another option is creating a new stud wall containing the insulation, with the option of attaching extra insulation on top. Clearly, it encroaches on space somewhat, but it can be a good way to avoid damp. Material options include:

  • treated sheep wool (great insulating qualities, 100% natural, non-flammable, regulates moisture)
  • rigid boards

Space-saving alternatives

Wallrock thermal liner

Wallrock goes on like wallpaper and can be installed yourself. It prevents heat escaping through walls, prevents condensation and helps muffle sound. It is just over 3mm thick and is a smooth, plain white finish that can be decorated over as you choose. These products are cheap, quick to fit and will hardly increase the width of your walls – unlike other materials, which are typically 100mm thick.

External wall insulation

External wall insulation is the most efficient solution out there – and it won’t affect the size of your rooms or mean you have to redecorate. It can also be installed with minimum disruption to the household. If you think other measures don’t go far enough, it’s definitely something to consider.

Installing solid wall insulation

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