Even though insulating an outdoor sauna is not mandatory, we recommend adding insulation to your purchase if you’d like the outdoor sauna to heat up quicker and stay heated for longer. Moreover, the black alder finish that comes with the insulation package has a smoother texture, which is better in the long-term than the usual conifer timber finish. If you’re thinking about opting for insulation, we’d be happy to consult you at 02070994301!