Household retrofit guidance for private properties Internal walls

Internal wall insulation is a good option for homes with solid walls, especially when external insulation isn’t possible due to heritage or appearance reasons. 

It is also a suitable option if you are insulating one room at a time as part of a phased renovation.

This method can be more disruptive than external insulation, so it's best to plan it along with other home improvement work.

There are different types of internal wall insulation, such as: 

  • rigid boards attached to the wall
  • timber frames filled with insulation
  • insulated plaster

A retrofit specialist can recommend the best option for your home.

The Energy Saving Trust provides comprehensive guidance on how to insulate your internal walls.

The Centre of Sustainable Energy has useful advice for somebody thinking about internal wall insulation for the first time.

Modern timber house construction with rigid insulation boards.

Risks

Moisture can build up behind internal wall insulation. Using breathable insulation products can help prevent this. 

Whenever you fit solid wall insulation to a building, you will need to take account of water vapour.

Speak to your specialist installer about creating a moisture control plan tailored to your home.

Other things to consider include continuing internal wall insulation between floors, most notably between floor joists. This is to ensure a continuous insulation line is wrapping the property. If possible, plastering the area between floorboards can also improve air tightness.

Regulatory considerations 

  • internal wall insulation typically does not need planning permission unless the property is listed
  • listed building consent is required for listed buildings
  • making major changes to walls, roofs, or floors may need building regulations approval through a building control body
  • internal wall insulation usually doesn’t need planning permission unless the property is listed
  • listed buildings require Listed Building Consent 

The relevant building regulations which are required include: 

Part F (Ventilation)

Part L (Energy Efficiency)

Part P (Electrical Safety).

Cost: £10,000 pounds

Disruption: High