I'm coming across this with floor insulation, too. It goes like this: We're putting a wooden floor down on joists. Under the joists I'm thinking about a sheet of plastic; between the joists a load of polystyrene from the tip; then subfloor; then floor.
The books say air needs to flow under the wood, if necessary by adding airbricks. But I can't see how air is going to flow anywhere with all that polystyrene, the airbricks would be below ground level and it gets down to minus 12C here in the winters, which would make for a very cold floor and defeat the object of putting insulation there anyway. Think higher heating bills. And a friend with floor-fitting experience says no one he's working with had airflow under wood they laid down. So I'm tempted just to go ahead and deal with the consequences (which is what I do with most things, which is why I have far too much work to do and am very tired, but fit).
My partner suggested sprinkling some eucalyptus oil on the fleece. I think. I'll have to ask.
Anything to do with environmental building projects.