The mobile-sauna is born after the tough winter 2012 willing to fight against cold shaking fatality. A movable and heatable space needs to be designed. “nature always acts by economy…P.Berger” So we attend to use as less material as possible to compose an auto-stable and airproof envelope. The hexagone appears as the geometrical figure able to resolve these problems. The sauna is formed by 6 similar panels compressed together by 2 truck straps while the roof equilibrates the variable pressures. Simplicity and efficiency of the structure allows to introduce spatial complexity on the inside by a series of stacking bench in the overall space.