Almost a third of heat loss in uninsulated homes occurs through the walls.

Homes in the UK are built either with solid walls or a cavity wall. A cavity wall is two walls with an opening between them. Not having insulation in the space between the two walls makes it easy for heat to escape from your home. Warm air always moves toward colder air, so in the winter you are losing heat to the outside and in the summer hot air moves inside your home.