Cedar is the best type of wood for a wood burning hot tub, specifically western red cedar and Alaskan yellow cedar. Its high tannin content makes it naturally waterproof and resistant to decay, wood rot, and warping, even after bring submerged in water for extended periods. Alaskan yellow cedar has a beautiful color and is known for its clear and smooth grain, but it's expensive. Western red cedar is the most popular choice for a wood soaking tub. It has the same durability and toughness as Alaskan yellow cedar, but costs less and has a distinct earthy, reddish hue. Plus all cedars smell fantastic. In terms of heating, the best type of wood to use as fuel in a wood burning hot tub is seasoned hardwood, such as oak, birch, maple, or ash. Hardwood burns slower and produces a greater amount of heat than softwoods like pine or cedar—these should be avoided as they contain resin that can create a buildup in the stove and stovepipe and affect water quality.