Well, I've got the foil rig (about 3/4 of the mesh) that I got from one of the posts on here. That helped a lot (I was around 30% humidity at first!!).

So you just put a damp towel over the top? Should I take off the foil for the towel or just cover the rest of the mesh with it?

I hope he'll get on with it and finish his shed today or tomorrow!