Insulating Walls: Traditional Construction

Properties built using traditional forms of construction need to be treated differently. The various forms of earth construction used are unlikely to require additional insulation, but great care must be taken not to trap damp within earth walls, as this will lead to rapid decay of the structure.

Oak framed buildings are single skinned, meaning the oak framework is visible both inside and out, and the space between the timbers is filled with various materials. Covering such structures externally with anything other than a breathable cladding will lead to decay of the timbers, not to mention the loss of character.

Such walls can be insulated internally but, again, this will result in a loss of character as the timber work will be concealed. It is therefore unlikely that the walls of an existing oak framed house will be upgraded. However, where a building such as a barn is being converted and the Building Regulations require oak frame walls, the infill panels can be replaced with a build-up that includes a layer of high-performance insulation board, sealed around the edges with a neoprene seal, covered in a new layer of render on mesh on the outside, and skimmed plasterboard on the inside incorporating a damp-proof membrane.

Insulating Cavity Walls

How to check if you have a cavity wall
Chances are, if your home was built between 1920 and around 1990 it will have uninsulated cavity walls (unless a previous owner has insulated them). You can tell by the pattern of your brickwork. A regular pattern (ABOVE, TOP) indicates that the external wall is non-structural; an alternating pattern (ABOVE, BOTTOM) shows that the wall is double skinned and therefore structural. If your brickwork is covered, then you can usually tell by the thickness of the walls: go to an external door and if the depth of the wall is less that 260mm deep, it’s probably solid.

Has the cavity already been insulated?
If you have a cavity, you could drill a small hole (known as a boroscope inspection) in your external wall to see if the cavity is hollow or filled (drill low down the wall, as the insulation is likely to have dropped). If you’re unsure, get a registered installer out.

How does it work and how much does it cost?
Cavity wall insulation is blown into the cavity from the outside of the house. The type of insulation depends on the supplier but companies offer urea formaldehyde foam, blown rock or glass-wool fibres, or polystyrene spheres. Find an approved registered installer who will be able to offer a 25-year guarantee through ciga.co.uk. If the house is not detached, the installers should insert a cavity barrier to ensure that the insulation doesn’t affect/benefit neighbouring properties. A typical installation will cost £250 (after grants) and, according to the Energy Saving Trust, will save you £160 a year on your bills.

What to look out for from installers
Installing cavity wall insulation is a relatively straightforward job, so you shouldn’t get too many problems — but look out for the angles the installers use to inject the insulation in order to ensure proper fill around windows, a failure to clear out ventilation bricks and also a failure to prevent the injection from spreading below the DPC.

The Grant Situation

Well, in short, it’s not good. Solid wall insulation falls outside of the generous incentives offered through the Government’s recent CERT schemes in collaboration with the energy companies — which seems incredibly short-sighted as there are more homes with solid walls than cavities, and solid walls lose more heat than those with cavities. The situation for cavity walls is thus: if you’re over 70 or on benefits you’ll get it free; if not, you’ll still get grants of up to £400 off the installed cost, which means you’ll end up paying up to £250.

The only help available to those with solid walls is through some local councils, who have bought into schemes with specialist suppliers. You’ll have to choose their approved product, which you’ll get at a discount. Best to contact suppliers/installers to keep in touch with the (ever-changing) situation. The good news is that you will pay the reduced VAT rate of 5%.

• Insulating Walls
• Internal Wall Insulation
• External Wall Insulation