The main supporting structure is made form steal beams with section dimensions of 100 x 100 x 3 mm. This kind of constructions ensures a quality support for the floor and ceiling grids and as a framework for the inner and outer walls. The adjustable legs ensure a leveled installation on uneven terrain. The metal brackets used for the transportation are also used for joining them in larger compositions ensuring a strong and watertight connection. If needed a custom unit can be made with different dimensions of the metal framework and by that increasing the thickness of the thermal insulation giving it better performance.