Cavity wall insulation
If your home was built after the 1930s, the chances are that its external walls are made of two ‘skins’ with a small gap between them. This means they are ‘cavity walls’ and the gap between them can be filled with insulating material to stop the warmth escaping to the outside.
The cavity can be insulated by drilling a series of small holes into the mortar at regular intervals and injecting the insulation material into the cavity. The holes are then refilled.
There are two types of cavity wall insulation material available through the Energy at Home Scheme; mineral wool fiber, or polystyrene beads. The mineral wool fiber has been used effectively for many years, however the polystyrene beads are more efficient at keeping the heat in, and are water repellent.