PURPOSE: To prevent deterioration of a building frame due to dew condensation by providing a heat insulation layer made by glass wool and/or resin foam in such a manner as to closely adhere to the outside of an outer wall, providing an air permeable layer on the outside thereof, and providing a facing material thereon.

CONSTITUTION: After a heat insulating layer 2 made by glass wool and/or resin foam is provided in such a manner as to closely adhere to the outside of an outer wall 1 of a reinforced concrete construction, an air permeable layer 3 is provided on the outside thereof and a facing material 4 is provided. The layer 3 is forced to conduct with the outside air by natural ventilation and mechanical ventilation. Subsequently, the outside air is introduced from below the layer 3 and discharged from the upside of the layer to make the layer 3 as the external environment. The outside heat insulation surely exhibits its effect by the construction of the outer wall 1, so that there is no spot exceeding the saturated vapor pressure, and as the humidity transmitting resistance of the outer wall 1 is comparatively large, the quantity of water emitted from the interior is small not to cause dew condensation. Thus, it is possible to prevent deterioration of building frame such as the outer wall 1 or the like due to dew condensation.