If your house was built after the 1920s, it could be a hollow wall. If it has not been built in the last 20 years, these cavities may be empty. If this is the case, filling the wall insulation can be a very economical way to keep the heat in your home and save energy costs.
Approximately one third of the heat loss in most homes is through walls, so cavity insulation can save up to 160 pounds per year for heating. In fact, according to the website of the Trust of Energy Conservation, he can pay for himself in less than five years.