I keep both my reptiles and rats in my shed. The shed is very well insulated with a drop down insulated ceiling and ridge venting. I heat it with an electric baseboard heater and cool it with a window air conditioner and box fan. As long as I keep the air moving and the bedding clean, I have had no issues. When I clean in the summer at night I leave the door open, but thats the extent of the ventilation. Everybody does fine.