Abstract: An improved building structure that eliminates condensation at exterior building walls, thereby preventing mold growth and avoiding the damage, environmental degradation and health problems associated with mold growth includes enveloping spaces that allow natural convection of air in exterior wall structures and roof structures. An embodiment of the building structure includes an exterior wall structure defining an air gap between insulation and exterior sheathing, a roof structure defining an air gap between thermal insulation and a roof deck, the wall air gap and roof air gap being in fluid communication, a roof vent to allow air to flow to an outside space, and an air ventilation grid at the lower end of the wall air gap. The air ventilation grid includes openings that allow air to freely enter the wall air gap and flow upwardly by natural convection into the roof air gap and out of the roof vent.