If your home was built before 1919, its external walls are probably solid rather than cavity walls. Cavity walls are made of two layers with a small gap or ‘cavity’ between them. Solid walls have no gap, so they let more heat through.
Another way to tell is by measuring the width of the wall. Look at an external wall window or door and if the brick wall is less than 260mm, then it is likely a solid wall, while if it is greater, it is probably a cavity wall.
If you live in a house that is not made from bricks, such as a steel or timber-framed building, insulating will be different.
Solid wall insulation
Solid walls can be insulated – either from the inside or the outside. This will cost more than insulating a standard cavity wall, but the savings on your heating bills will be bigger too. You might be able to reduce these costs by carrying out the work at the same time as other home improvements or by not tackling all the house at once.