Wall insulation

On the programme on 19 January 2026, we looked at some of the problems homeowners have faced after having solid wall or cavity wall insulation.

• Solid wall insulation is an extra layer of insulation on an external or internal wall, while cavity wall insulation is injected into the space between the two layers that make up the external walls. Most homes built after around 1920 have a cavity like this, whereas older homes probably don’t.

• While we highlighted some of the issues that have arisen from poor quality insulation, if installed properly, both types of insulation can provide huge energy efficiency savings, leading to lower heating bills by trapping more heat inside your home.

• Energy Saving Trust estimates that around a third of all heat lost in uninsulated homes escapes through the walls. It has more information on the importance of wall insulation on its website here.

Installation

Both types of wall insulation should be professionally installed to ensure compliance with regulations and to provide an appropriate guarantee. Trustmark may be able to help you find a professional installer. Guarantee body SWIGA, which featured in our programme, holds a register of members on its website.