I have a 2016 Caldera Martinique Hot Tub. The tub is located under my deck. There are walls but no drywall walls.. just wood slabs and a barn door to keep the elements out. I live in the mountains. ...so snow in winter and hot in summer. Do I need to cover my hot tub if the elements can't get in and there is decent ventilation? Can I just keep it open and refill when it gets low?