Will Spray Foam Insulation Under the House Cause Damp Issues
Information, help, tips and advice on cavity walls, ceilings and lofts etc....

whiskyowl
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Will Spray Foam Insulation Under the House Cause Damp Issues

by whiskyowl » Thu Oct 26, 2017 9:35 am

Hi everyone!

Please excuse my ignorance about insulation. I am in need of advice!

I'm currently having an extension built on my 1920s semi. I have a one-off opportunity as part of this to get underneath the existing house and insulate it from the crawl space. There is currently no insulation at all in place apart from the high quality underlay I put down underneath a wood floor (which has made a big difference).

However, the house is on a hill and the crawl space varies in height from about 45cm at the front to nearly 160cm at the back.

Here's the problem: when I moved in, I had problems because there was insufficient air circulation at the front - I had to get some joists redone and put in quite a few airbricks to increase ventilation. I'm obviously keen that these problems don't come back.

Will insulation with spray foam (open cell) cause damp? How much clearance should I leave underneath the house at the narrowest point to ensure I'm not making a rod for my own back here?

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