Insulating walls will help to conserve energy, but the methods employed are more expensive.
Insualting cavity walls
Insulation can be injected into cavity walls. Cavity walls can be filled
with moisture-resistant plastic foam or mineral wool.
Unless the cavity
walls have been filled during the building stage, a contractor will have to
be employed to inject the insulation in the cavities.
Insulating internal walls
Internal thermal boards can be fitted to the inside surface of the wall.
It is particularly beneficial to line cold outside walls, especially those
facing north or east. Use foil-backed plasterboard nailed to battens.
Firstly fix battens on the wall and then fix the thermal boards to the battens.
This will leave a gap behind the board, which will trap a layer of still, dry air -
similar to double glazing your wall!