If you have a barrel or cabin sauna. Have you treated the exterior? And with what? I am trying to decide if I should cover the exterior of my cabin sauna with 1.5 inch insulation and LP siding or just stain it every year. I am worried the boards may warp or open up over time. Also a simple 2 x 6 is only rated at about R-5 insulation. Anyone had issues when its 0 deg outside?