Abstract: An improved building, e.g., a greenhouse structure, is provided herein. It consists of an enclosure having a pair of spaced-apart walls, e.g., an outer light transparent covering and an inner light transparent membrane spaced apart from the outer covering. A fan is provided for charging the space between the covering and the membrane with air, under pressure having a dew point so selected that it will not allow condensation to take place, e.g., outdoor air, or, preferably, heated air. An insulating layer is disposed in the pressurized air space between the outer covering and the inner membrane so that it is bathed, on both its faces, with the low dew point air under pressure. The insulating layer includes an insulating blanket disposed between the outer covering and the inner membrane, and is positively movable between an extended covering position and a retracted stored position.

Abstract: A system for utilizing the exhaust gases from a hydrocarbon combusting apparatus to enhance plant growth comprising an enclosure for plants having an outer covering and an inner permeable membrane spaced from the outer layer, the membrane being less permeable to toxic gases, present in the exhaust, than to CO.sub.2, and means for conducting the exhaust gas from the hydrocarbon combusting apparatus to the space between the covering and the permeable membrane. In the preferred embodiment, the outer covering and membrane are transparent to light.