Grant,
My plastic roll off shed, described here: https://britastro.org/node/11048
is pretty much condensation free; the plastic walls stay dry, although the plinth gets very damp due to its sheer thermal mass.
All my wooden sheds attracted gigantic spiders, some the size of small dogs………. (OK, a slight exaggeration, maybe)
The plastic shed attracts snails….they even scale the plinth and sit on the C14 dovetail sometimes! But the spiders stay well away from the plastic….. Of course, my sheds are complete roll-off systems, not run-off roof systems.
Martin