Household retrofit guidance for private properties - Cavity walls

Cavity walls have 2 layers with a gap in between, usually made of brick on the outside and blockwork inside. This gap can be filled with insulation to help keep your home warm without changing your property’s appearance.

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Insulation guidance

• Before insulation, an assessment should address any cracks or damp issues in the walls.
• Choose a trusted installer registered with the Cavity Insulation Guarantee Agency (CIGA), which provides a 25-year guarantee.
• Inject material through small holes in the outer wall, which are then sealed afterwards.
• If there are damp patches on your interior walls, do not insulate them until the issue is fixed.
• Consider insulating your roof or loft at the same time for better overall insulation.

The Energy Saving Trust and the Centre for Sustainable Energy provide guides to installing cavity wall insulation. 

The Planning Portal provides a useful introductory guide to the building regulations required for cavity wall insulation.

Historic England provides advice on energy efficiency and historic buildings: early cavity walls.

Regulations

• Cavity wall insulation does not usually need planning permission unless the property is a listed building, which will need listed building consent.
• Major changes to walls, roofs, or floors often require building regulations approval.
• The cavity wall installer should be able to submit a notice to a building control body on your behalf.

Relevant building regulations required include: 

• Part A (Structural Safety) 
• Part F (Ventilation)
• Part L (Conservation of fuel and power)

Cost: £500

Disruption: Low to Medium