Internal Wall Insulation

Internal Wall Insulation (IWI) is an extremely effective means of insulating solid wall properties that can not add External Wall Instulation such as listed homes. This helps to significantly reduce the amount of heat lost through the walls.

The installation process involves fixing a layer of insulation material to the internal walls of a property, finished with plasterboard to leave a smooth and clean surface for redecoration. Decoration and the movement of fixtures and fittings are generally included within the installation package.

Cornerstone specialises in the insulation of solid wall properties and has internally insulated countless domestic properties all over the UK, including private and social housing, as an alternative solution to External Wall Insulation (EWI).


Uninsulated solid walls can leak up to 45% of a property’s heat – insulating these walls can save up to £425 per year on your energy bills.* Solid walls can be insulated internally or externally, with the cost depending on the property size and condition. Internal Wall Insulation (IWI) offers a number of benefits:

  • Creates a warmer and more comfortable home
  • Significantly lowers your energy bills
  • Improves the appearance of your property
  • Can be carried out on a room-by-room basis
  • Prevents condensation and mould growth
  • Increases the value of your property

Grants available

Depending on your households circumstances, funding could be available to contribute towards the cost of IWI.


If your home was built before 1920, it will most likely have solid external walls with no cavity. The lack of a cavity means more heat can escape from your house through the walls.

Internal wall insulation is applied to the internal face of a property’s external walls and can often be the single biggest home improvement you can make to reduce heat loss. The insulation makes it much more difficult for the heat to pass through your walls, keeping as much of it as possible inside your home for as long as possible.

IWI is suitable for all properties but is most often installed in homes where External Wall Insulation (IWI) is not appropriate, such as listed buildings or those located in a conservation area. While IWI may impact internal living space and be more disruptive throughout installation, it is often cheaper, quicker and less complex to install than EWI and won’t require planning permission.