A Guide to External wall Insulation

How do you know if you have solid walls or cavity walls:

As mentioned above if your house is in the UK and was built before 1920-1925 then it probably has solid walls. The easiest way to confirm this is visual if you have un-rendered brick walls and you can see the ends as well as the sides of the bricks then you have a solid wall.

Solid walls can be insulated through either from the inside or the outside. This will cost more than insulating a standard cavity wall, but the savings on your heating bills will be bigger too.

If your walls are rendered, then you’ll have to measure the thickness of the external wall. This is easiest done at a doorway or window opening. If it’s 230-250mm you probably have solid walls although some early cavity walls were 250-270mm a modern cavity wall would be 300mm plus.

Solid walls don’t trap heat efficiently and twice as much heat can escape through them as through cavity walls. Upgrading them with external wall insulation is a great idea, as not only from it you will save on your energy bills, but you'll also protect your home by preventing damp and give the exterior a makeover.

External wall insulation, also known as EWI and external solid wall insulation, is a type of insulation that is attached to the outside of your walls. Two layers of material are used - one to offer insulation, and an outer layer of mineral or synthetic render to protect against the weather and provide a decorative finish. In simple terms External, Wall Insulation is a system of components that can be applied on the outside of a building to insulate, protect, and enhance it. 

The External Wall Insulation Installation Process

• Adhesive mortar is used to fix the prefabricated insulation panels to the outside wall.
• Special fixings are used to secure the panels to the wall.
• The insulating panels and fixings are then covered in mortar.
• An insulating mesh is then fixed to the mortar to hold everything in place safely.
• Once the mortar sets, it's sanded and painted in primer to prepare for the final stage.
• Render and the colour is applied as per the clients choice.

External wall insulation involves adding a decorative weather-proof insulating treatment to the outside of your wall. The thickness of the insulation needs to be between 50 and 100mm and is usually installed where there are severe heating problems or the exterior of the building requires some form of other repair work providing the opportunity of adding insulation.

Advantages of exterior wall insulation:

The advantages of exterior wall insulation are fairly well detailed above so I’ll just list them again here:

• Avoids cold bridging.
• Won’t cause you to lose valuable floor space internally.
• Let’s the thermal mass of the walls work as a heat sync.
• Means your home will look new again from the outside.
• Can reduce future external redecoration costs.
• Increases the thermal efficiency of your home dramatically.

Disadvantages of exterior wall insulation:

External insulation is expensive and typically is around twice the cost of insulating internally. On the other hand, internal wall insulation will involve extra costs such as relocating radiator pipes away from the walls, replacing flooring, relocating fireplaces out from walls and redecorating and other related things.

Planning Permission and Building Regulations 

It is recommended that the Local Authority Planning Office is contacted to ascertain if there is a need to apply for planning permission. For larger schemes, the Housing Association should be able to provide advice if a Planning Application has been submitted and granted. Information on Building Regulations applications is also contained on the Planning Portal and again advice should be sought from the Local Authority before carrying out any Building work.

How Much Does External Wall Insulation Cost?

Typical installation costs* of external wall insulation can vary and can cost around £13,000. The cost of insulating walls externally is around £100 per square meter, so it can range from £8,000 for a small flat up to £22,000 for a large detached house

Does external wall insulation prevent damp?

External wall insulation is, of course, a great way to reduce condensation based damp! Ensure the walls are nice and dry and free from any moisture when installing external wall insulation. The best time to carry out the works is between May and September when the weather tends to be stable and dry.

The external wall insulation will form a cosy blanket around your house, which will change how the inside of your home behaves. External wall insulation can prevent future damp on walls from condensation but it won’t mask existing problems of water penetration. If you have burst to the gutter, roof problems or rising damp, make sure you get those items repaired at the same time, or prior to the insulation being installed on the walls.

External wall insulation will keep your home nice and cosy and with all other elements addressed prior to application keep the property free from damp.