One important factor in your sauna will be the type of heater you use, but you will also need to pay close attention to the size and height of your sauna to ensure they are evenly paired with your heater. Waterproofing and ventilation are also significant contributors to sauna maintenance and should be considered right from the planning stage. Don't underestimate the importance of decent accessories either; these can go a long way to improving your sauna experience.
Proper ventilation in your sauna ensure that you're breathing fresh air, and help circulate heat around the room.
The size of your sauna affects how much fuel it uses, how long it takes to get hot, and how comfortable it is.
The accessories you choose for your sauna will allow you to use it the way it's meant to be used.