Insulating wall unit

In a wall unit comprising panels lying at opposite faces of said unit and defining a cavity, a seal arranged between the margins of said panels to air-tightly seal the wall unit, insulation means occupying the cavity between said panels, said insulation means comprising at least one insulating group extending parallel to said panels and composed of at least two foils capable of reflecting thermal radiation, and chambers lying between said foils, the walls of said chambers consisting of insulating material, and atmosphere control means associated with said wall unit and communicating with the interior thereof for continually maintaining a dry gas atmosphere within said wall unit thereby preventing condensation of water vapor therein, said atmosphere control means comprising pipes, gas drying means, dust filtering means, and pump means for circulating the dry gas through the cavity;

• said pipes, gas drying means, and dust filtering means being connected with each other and the cavity of the wall unit and forming a closed circulating system.