cavity wall insulation

[Anonymous]

We have a Victorian house with a 100mm cavity and are considering having the cavity filled! We have spoken to Rep's regarding using Rookwool or polystyrene beads being blown in. Has anyone had any experience or comments/ things to look out for/ environmentally sensitive solutions? Thanks.

Pete

[Paul Kent]

Where did you find a victorian cavity wall, as far as I knew they didnt become standard until the 1930s and 100mm cavities didn,t exist until the late 80s

[David Olivier]

I agree about 19thC. cavities they're not uncommon in Wales and the West Midlands. By contrast, parts of East Anglia have little driving rain and there one can find solid-walled buildings which seem to have been built in the 1950s/1960s. I think the 1930s is the *average* date when Britain shifted to cavity walls.

Unfortunately, you can't get a really good level of insulation from either 100 mm of mineral fibre or polystyrene beads. A U-value of 0.35 W/m2K is probably the best possible, even if the cavity isn't bridged by bricks. Admittedly it's better than the average Victorian house. If a cavity is also partly filled by rubble, you could be better off treating it as a solid wall in need of external insulation.

David.

[Author]

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