Should we insulate our cavity walls?

Postby katelje » Thu Sep 25, 2008 11:30 am

We are thinking of insulating our cavity walls. We like the idea of a warmer house and lower gas bills. However we have heard about problems with damp etc developing as a result of insulation. Has anyone any thoughts on the matter? Has anyone insulated their walls and been happy with the result? Kate
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Simply Build It

Postby Perry525 » Tue Sep 30, 2008 5:49 pm

I imagine you are thinking of blown insulation placed inside the cavity.

The significant problem with this is, if the outer skin of the wall is not totally water proof. Then the water running down the inside of the outer wall will make the filling wet, this will make the inner wall wet, then heat will be conducted from the room through the wall and you are worse off.

Some people have been lucky and the job has been done properly, no gaps left inside the wall (I have seen gaps 3 feet deep and 18 inches wide where the filling has been skimped and you cannot tell if its been done properly without access to a thermal imaging camera)

A better bet, is a waterproof outer skin, dry walls = good insulation and either extra insulation on the inside or outside of the walls. The optimum is five inches of polystyrene or similar.
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Postby welsh brickie » Wed Oct 01, 2008 9:54 am

there are some grants available for cavity wall insulation so try applying to your local council.
Yes it is worth it ,and I prefer the polystyrene ball fill insulation than fiberglass because it tends to be more water resistant and fills the cavity better.
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