A solar greenhouse which may be modular, free-standing or erected against an adjacent structure such as the wall of a building, having s a frame including structural members such as extruded aluminum channels which support a glazing system of transparent or translucent panels. The transparent or translucent panels preferably are opaque to the transmission of infra red light rejected from the solar collector louvers and the interior of the solar greenhouse. Positioned within the solar greenhouse enclosure below the glazed roof or top are a plurality of rotatable solar collector louvers which may be individually positioned or preferably are rotated in unison by a drive system which may be manually controlled or controlled by a software program in a computer or microchip. The louvers are effectively flat plate solar collectors. Water is circulated through the tubular axle of the louvers and is heated by solar radiation when the louvers are in their solar collection positions. The louvers may be adjusted to various positions.
