These beasts are grown under fluorescent lights in my basement. At night I spray the Neps down and place a domed enclosure over them and then move them to the coolest place in the house, which currently is hovering at around 6C/44F.
During the day they are uncovered and only get humidity from the damp sphagnum they are growing in and the sphagnum in the surrounding Nep pots. Daytime temps are around 20C/70F.
It seems to be working for me so far.