A Guide to External Wall Insulation (EWI)
External wall insulation (EWI) can be applied to the exterior of homes with solid walls. It means you lose less heat through your walls.
Main benefits
- Reduces heat loss through the walls of your home, meaning that your heating system can be smaller and cheaper to run.
- It can be used at a greater thickness than internal wall insulation, reducing heat loss further.
- Will retain the ‘thermal mass’ of the building, reducing the effect of temperature changes throughout the day, and so maintaining a more comfortable temperature in your home.
- Provides a new façade, which for some people will be an opportunity to refresh the house’s look.
Things to consider
- Changes the appearance of the house: there are a variety of finishes available.
- Planning permission may be required, and in some cases, it may not be granted, for example, for period properties or in conservation areas.
- Needs to be designed to avoid condensation and heat loss through ‘thermal bridging’.
What options are available?
- There are many finishes available. For example, renders in any colour, brick slips, tiles, timber cladding and decorative boards.
- Depending on the building’s construction, different materials may be used for the insulation layer. For example, mineral wool, woodfibre, cork or expanded polystyrene.
