If you’re looking to improve your home’s thermal efficiency and lower your heating costs, then you will likely have looked into different insulation options. For solid walls, the two insulation types are external wall insulation (EWI) and internal wall insulation (IWI), but is it better to insulate inside or outside?

It’s important to note that both these options will improve your home’s thermal efficiency; however, we believe that, of the two, external wall insulation is superior. There are a few reasons for this, which we will outline in this blog.

EWI can provide more insulation

While insulating either the inside or the outside of your home will improve its thermal efficiency, the thermal values of external wall insulation are consistently much higher than internal lining insulation. In fact, external wall insulation can reduce your annual heating bills by as much as 50%. This is because the walls are warmed by your home’s heating system and will release the heat back into the home when the heating is turned off, maintaining a steady temperature.

EWI doesn’t limit your interior floor space

One major benefit that external insulation has over internal insulation is that it doesn’t limit your interior floor space. IWI needs to be installed on the internal walls of the property, meaning that each affected room becomes a little smaller. Because EWI is installed entirely on the outside of the property, this isn’t an issue.

EWI provides better protection for the home

Another reason that insulating the outside of your home is better than insulating the inside is that an EWI system protects the structure of the building. Because it is covered, the brickwork is protected from weather that could damage it. EWI also prevents penetrating damp from entering the home and eliminates condensation. As well as protecting your home from the elements, EWI also protects it from noise, significantly dampening sound from the outdoors.

EWI requires little pre-prep and doesn’t disturb your home life during installation

When you have insulation installed on the inside of the property, you need to prepare the interior walls for the system to be fitted. This means that you will need to remove any decorations as well as any fittings such as light switches and plug sockets so that they can be rewired through the new wall.

Additionally, the team installing the insulation will need to be inside your home during the work, putting the rooms off-limits until the work is done as there is likely to be significant mess and disruption. With EWI, all the work is done outside of the property, meaning you don’t have to do much in terms of preparation, and the work shouldn’t affect you going about your day as normal.

EWI allows you to redecorate the exterior of the property at no extra cost

Insulating the outside of the property also means you will get to choose a new aesthetic for your home’s exterior. EWI systems are created in layers and the top layer is finished with a coating such as a marble aggregate or a silicone resin render with different texture options such as a travertine or floated finish. These renders are also available in a range of colours, meaning that you get plenty of choice when it comes to the appearance of your home (that is also now much more thermally efficient).


Both types of solid wall insulation have benefits, will save you money on your heating bills, and reduce your carbon footprint. However, for the reasons above, we believe that insulating the outside of your property is the better choice.

If you are interested in external wall insulation, please do get in touch with us.