For the sauna interior it is recommended to use deciduous trees materials. The most popular tree species used for sauna  materials are aspen and black alder.
These tree species are able to provide high moisture resistance and temperature fluctuations for a long time, which preserves the sustainability. Compared to coniferous tree, deciduous trees have better thermal conductivity, retain heat more efficiently indoors, and help create an even heat distribution. Deciduous trees have a natural aroma that gives an additional sense of relaxation. Compared to other materials, deciduous trees are less likely to cause allergies. They are suitable for people with more sensitive skin or respiratory  problems. Aspen and black alder materials are natural and sustainable resources that do not have a significant impact on the environment. Using these materials, it is possible to create high-quality and comfortable and at the same time environmentally friendly saunas.