All greenhouses collect solar energy. Solar greenhouses are designed not only to collect solar energy during sunny days but also to store heat for use at night or during periods when it is cloudy. They can either stand alone or be attached to houses or barns. A solar greenhouse may be an underground pit, a shed-type structure, or a hoophouse. Large-scale producers use free-standing solar greenhouses, while attached structures are primarily used by home-scale growers. This online guide describes amny deisgn and construction methods.