The roof is going to be 6" of poured concrete. together with the slope, water shouldn't get in.
There is going to be a 2" HD foam cover glued to the roof as well for insulation and 5ft of soil above this. Humidity, I expect, will be pretty much naturally maintained at around 80%. I have installed sprayers along the walls as well if needed.
The goal is to make an ideal environment for Cheddar. SAFE Cheddar!
The recent cases of Morningland and Estrella are giving me lots to consider.
JD, this(Product Safety??) may be a subject for a new major heading. There seem to be quite a few of us on this wonderful forum going commercial.