hello Steamy tea,
yes NE Italy so fairly moderate climate 10 months of the year (rainy May, snow Jan, its on a mountain).
There shouldn't be too much water vapour inside, its just me and my paintbrush, it will be my studio. Mainly thinking of the cold few weeks in winter. The roof will be torched with lime but there will still be some ventilation through them too. I have seen a guy who used twin wall polycarbonate sheets. These are light weight and would trap air from a cold wind but could provide some ventilation in places.