The walls of your home do many different jobs at once. They support the roof and the floors, keep the heat in and keep the rain, cold and noise out. You will have to act fast if the roof is falling down, but millions of people survive with poorly insulated walls simply by turning the heating up. Getting your walls to work properly in every respect is therefore a top priority for greening up your home.
Warm, green and cosy
Walls with no insulation throw heat away with abandon. Installing insulation can be a major task, given the area you have to cover, but you will definitely feel the results: warm walls make for a green, cosy house. Remember that it is only your exposed external walls that you have to fix, as you can assume that walls adjoining other properties will gain as much heat as they lose
As well as cutting your heating bills by up to a third, insulated walls improve the comfort of your home, prevent condensation forming on your walls and keep the heat out on hot summer days. If however there are any existing problems with your walls, such as damp, you should address these first or you may make matters worse.
Cavity wall insulation
Many houses built in the twentieth century have double-skin walls with a cavity betwen the two layers. The aim of the cavity is to prevent moisture getting through the wall and into the house. It is also an ideal place to retrofit insulation by blowing it in through holes drilled in the outer wall. The insulation is typically made of polystyrene beads or fragments of mineral fibre which fill up all the nooks and crannies inside the cavity but prevent moisture from tracking across the inner wall
Cavity wall insulation requires professional installation, but this is usually staightforward and takes less than a day. Once the insulation has been blown in to the walls, the holes are made good and the building is left with no significant changes to its appereance
Solid wall insulation
Most houses built before 1930 have solid walls waith no cavity. You can only improve these walls by adding insulation to the inside or the outside. Covering entire walls with a new layer of insulation and a new finish is a big and messy business, so it is worth undertaking with other renovation tasks.
The simpliest way of adding insulation to a solid wall is to stick it on the interior face. Use plasterboard which is designed specifically for this purpose with a layer of high performance insulation already attached. The thicker the insulation layer, the more energy you will conserve. You can do better still by building a new wall in front of the existing one with timber or metal uprights (studs). You can then pack the gaps between the studs with 100mm of insulation or much more. Internal insulation must include a barrier (a polythene sheet uner the plasterboard) to stop water vapour getting into the wall where it could condense on the masonary behind the insulation. This barrier is included in insulated plasterboard products.
The depth you choose will partly depend on how much of your room you are willing to lose (only the exterior walls need insulating, remember) and how many window sills and architectural details you have to work around. If you do not want to lose any of your room space, you could still install thermal wallpaper. This thick lining paper will not do much to cut your heat losses but it will give you warm, condensation-free walls