Insulation

What are the different types of insulation?

Most heat within a home is lost through the walls, floor, and roof. Insulation can help to reduce the amount of heat being lost through the home.

It is important to choose the right combination of insulation for a property. The correct type will depend on how the building was constructed (e.g. with a solid or cavity wall), the performance requirements for the retrofitted home, and whether there are any planning restrictions.

Insulation Type	Description	Example
External wall type (EWI)	EWI is usually installed for solid wall properties. A layer of insulation is fixed to an external wall; then rendered or cladded. A range of finishes can be applied, to try and keep with the previous look of the building prior to EWI installation, e.g. brick slip finishes. Depending on the area, planning permission may need to be obtained beforehand. This could include listed homes or those located in a National Park, area of outstanding natural beauty, conservation area or within a World Heritage Site. Planning authorities should be consulted prior to undertaking any works if there is any uncertainty on planning permission.
Internal wall insulation (IWI)	IWI is usually installed for solid wall properties. A layer of insulation is added to the inside of the property and will therefore not require planning permission (though it may require listed building consent). It will reduce the size of a room slightly and require the interior of the property to be redecorated. IWI may be particularly appropriate where the external appearance of a building needs to be maintained (for example, on a listed building).
Cavity wall insulation (CWI)	Homes built after 1919 are likely to have a cavity between an inner and an outer wall. CWI is not an intrusive process. Insulation in the form of mineral wool or insulating beads is pumped into the cavity via small boreholes from the outside.