I really like vision racks......all the snake racks I use either are heated with heat cable or heat tape, which is run the same on each level.... you will need a thermostat to control and maintain proper temps

........ Or you can make a rack super easy, then run heat tape along the back(instead of belly)

But now if your using heat tape/cable should make sure the 'rack' is heat safe and wont warp or melt you mentioned plastic crate -wonder if you mean the all plastic drawers like at target ...if so you'll want to be careful running heat in those, I wouldn't recommend it ..just for safety reason

Vision Products

now if you do have a room that stays rather warm/humid like in Cali/florida you wont need to run heat...