Insulating your walls is one of the most effective things you can do to reduce your heating bills and save energy. Up to a third of heat loss from a property is via the walls if they are not insulated, as heat travels quickly to the cold outside.
Most houses built in the last ten years or so will have insulated walls, but if your property is any older you should ensure that all the walls are properly insulated.
Most types of wall can be insulated, no matter how old the house, so it is important to understand what type of walls you have, before considering which of the wall insulation types will work best.
From the 1920’s onwards, most houses have been built with cavity walls; an inner and outer wall with a gap in-between. More recently cavity walls have been constructed with insulation built-in, but older properties will benefit from having the cavities filled with insulation if it hasn’t been done already. Wall cavity insulation could save over £100 per year in heating bills, and will only cost around £100-£350 to install.
Solid Wall Insulation
If your house was built prior to the 1920’s, it is probably constructed of solid walls. It is essential to insulate them as well as possible, as they can lose two times as much heat as cavity walls. A solid wall can be insulated internally or externally; it will cost a good deal more than cavity wall insulation, but the savings will be greater and it will vastly improve the comfort level in your home.
Other Types of Walls
Not all walls are made of brick or stone, and not all will fall into the category of a solid or a cavity wall. Some houses are constructed with steel or timber frames, others are made from pre-fabricated concrete.
Alternative types of walls like these probably won’t have a cavity to fill, but may be able to be insulated in a similar way to a solid wall. If you are unsure of the type of walls you have and whether they can be insulated, it may be best to contact a professional installer to assess the job.
Insulating a Solid Wall
Solid walls can be insulated internally or externally, and both come with their own advantages and disadvantages. Internal wall insulation can be fitted by fixing rigid insulation boards directly to the inside of the wall, or by building a stud wall and filling the gap to the external wall with mineral wool insulation.
Exterior wall insulation is done by fitting insulation boards or materials to the outer of the wall, then covering it with weatherproof render or cladding.
If you insulate a solid wall you are required to ensure that it complies with the current building regulations.
This means that once insulated, the wall should have a U value of no more than 0.30W/m2K.
If you are having the wall insulated by a professional fitter, they should make sure that the materials they use are up to standard, and also arrange the necessary approval from building control to carry out the work. To achieve the U value specified by building regulations, the insulation should have a thickness of 60-120mm depending on which materials are used.
The thickness of internal insulation is usually around 100mm, and will take up space in the room and reduce the floor area. It will effectively be covering the external wall, so any problems with damp may be hard to detect and should be dealt with prior to installation.
It can cause a lot of disruption during the installation, as the room will have to be emptied, and doors, skirting boards and door frames will have to be removed and re-fitted. You will have to consider the fixing of heavy furniture and fittings to the wall, as insulated walls will not hold as much weight as solid walls.
To insulate the walls externally there must be good access and the walls should be structurally sound. It causes much less disruption when being fitted, and does not affect the floor space internally. It will benefit the wall as it fills any gaps and cracks, and improves weatherproofing as well as the appearance of the wall.
It will help to prevent condensation on inner walls and reduce damp, although any rising damp problems should be dealt with before insulation is installed. You may require planning permission for external insulation, particularly if you are changing the outer appearance of your house, so it is advisable to check well in advance.
How much will it Cost?
Insulating a solid wall can be very expensive; internal insulation for a typical three bedroom house could cost around £5,500 – £8,500, while external insulation would be approximately £9,400 – £13,000.
Internal insulation is likely to save in the region of £445 per year on heating bills, and will save up to 1.8 tonnes of carbon dioxide. Insulating externally could save you up to £475 per year in energy costs, and save 1.9 tonnes of carbon dioxide.
The costs can seem prohibitive, and solid wall insulation could take 15-20 years to pay for itself. It may be more cost-effective to install insulation as and when you carry out other repairs.
If you are repairing the rendering or re-pointing walls, you could fit external insulation at the same time. Or if you are redecorating a room, or having a new bathroom or kitchen fitted, you could fit internal installation as part of the job.
Wall insulation is an essential part of an energy efficient house. Un-insulated homes can lose around a third of their heat through the walls, and you can make substantial savings on heating bills by improving the insulation of your walls.
Solid walls are more difficult and more expensive to insulate than cavity walls, but the savings are greater and you will improve the comfort level in your home with properly insulated walls.
The costs can be reduced by installing insulation at the same time as carrying out other work, and if your walls are currently un-insulated, it is something you should seriously consider.