I’m retrofitting our Edwardian end-terrace using wood fibre, and I wonder if there are any moisture experts on here…
Our house has a solid brick wall (220mm) with a solid sandstone outer layer (150mm). Where the joists sit, there is a gap of a few bricks and the joists sit about 100mm onto the brick wall. It’s just sandstone behind it.
This leaves about 120mm behind each joist (varies) of an air gap. I was intentionally NOT insulating between the floors, as I was hoping this bit of thermal bridging would make a difference the risk of the joists being too wet. We’re fortunate that practical moisture calculations (WUFI) have been done on similar constructions nearby so have largely used them.
However, given we’ve got this space, I wonder about sticking some insulation in this air gap behind the joists, keeping the ends nice and toasty. As we’re using wood fibre this would be highly hygroscopic too, potentially wicking moisture away from the joists.
What do you think? Would this make any difference? Any problems foreseen?