A Guide to Internal Wall Insulation (IWI)
Internal wall insulation (IWI) can be used in 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 if you don’t want to change the appearance of your house.
- Planning permission isn’t required even in conservation areas. (Though listed buildings may need listed building consent.)
Things to consider
- Reduces the area of rooms by about 40-110mm, along just the walls with an external face.
- Disruptive to install, because skirting, radiators, and electrical sockets need to be refitted. But can be installed one room at a time, or done when other renovation is being carried out.
- Needs to be designed to avoid condensation and heat loss through ‘thermal bridging’.
What options are available?
- Depending on the construction of the building, different materials may be used for the insulation layer (hidden by the wall finish). For example, rigid foam boards, mineral wool, wood fibre, or cork.
