autovents on roof windows and I run my dehumidifier and oscellating fan 24/7, vents shut to an inch at night and fully open in the sun, I leave bottom louvre open all the time for ventilation.
Iv also got 2 x solar fans but I dont think much of them although probably better than without in the full on summer sun.
Iv got a very nice bushy white rhino in there this year

Sorry just seen your ghouse is a way away doubt you could run eletric to it?
Also the gas/oil ghouse heaters actually create condensation I wouldnt bother with them, end of day the natural conditions for canna are alot harsher, cold is far more acceptable than condensation, it WILL just lead to moulds imo!...