Hi I have a 20 x 10 ft shed I have insulated the walls with foil back xtratherm and the roof with foil bubble wrap, I had to go behind the board and noticed the wood was wet, it is definitely not a leak as this was not a problem before I put boarding up. I was wondering if anyone would know what I can do to prevent this
Hutcho, where exactly is this dampness? Can you describe every layer of the wall from out side to in, and where it's wet?
Really you need a vapour barrier on the inside of the insulation, what happens is warm vapour from inside the (now well insulated) shed will get behind the insulation, and as it cools it can condense on and inside the wall fabric in the same way that you get condensation on the surface of single glazed windows. Fit a polythene VCL inside, after the insulation, and then board up over that (if you plan on boarding that is) should sort your problem.