To provide a ventilation layer being simple and effective in external thermal insulation on a roof face, prevention of dew condensation, warm air floor heating and thermal insulation on a floor face by providing the ventilation layer on an outer side of a roof and below an indoor floor.

A vent sheathing constituted by arranging absorption sashes having vent holes to obtain the ventilation layer in parallel like cross-stitch on a roof and a vent floor on the floor are put into patterns to apply flameproofing, rot proof, and insect proof treatment in order to create uniform flow on a plane. The ventilation layer having thermal insulation on the roof face, prevention of dew condensation, and floor heating by a warm air outdoor device on the floor face is completed.