Household retrofit guidance for private properties External walls

External wall insulation involves adding a layer of insulation to the outside of your home’s walls. It does not affect your room sizes, but you will need to think about how it changes the outside appearance of your home. You will need to try to match the existing finish as closely as possible.

The insulation is typically covered with a protective render coating layer or cladding, like brick slips or tiles. The depth of the outside wall insulation can vary between 50mm and 130mm, depending on the system used.

Benefits

Insulating external walls of your home provides benefits in the following ways:

  • improves the energy efficiency of your home
  • renews the appearance of outer walls
  • improves weatherproofing and sound resistance
  • helps keep warm air out during the summer
  • be installed without disruption to your household

A specialist installer from the National Insulation Association (NIA) should be sourced to undertake the installation work.

The Energy Saving Trust provides easy to follow advice on how to insulate your external walls of your home to cut heating costs and make your home more comfortable. 

The Planning Portal has important information regarding the planning permission required for external wall insulation and building regulations requirements. 

Risks

Whenever you fit solid wall insulation to a building, you will need to be aware of the effects of water vapour. Speak to your specialist installer about developing a moisture control plan specific to your property. 

Other things to consider include your roofline may need to be extended to cover the top of the insulation.

Regulatory considerations

  • external wall insulation is considered permitted development for homes not in conservation areas
  • any external materials used must be of a similar appearance to the existing home
  • planning permission is likely required for flats, maisonettes, and homes in conservation areas
  • listed buildings require both planning permission and listed building consent, though it might not be approved due to the impact on historic features
  • in conservation areas, external wall insulation at the back of the property and internal wall insulation at the front may be acceptable if the back is not historically important
  • major changes to walls, roofs, or floors usually require building regulations approval. The specialist installer can handle this process for you

The relevant building regulations which are required are: 

Part F (Ventilation)

Part L (Energy Efficiency)

Cost: More than £10,000 pounds

Disruption: Medium