The main reason passive solar greenhouses are so popular is that they allow for year round growing. Relying heavily on preplanning involving solar orientation, use of heat absorptive materials and a heat exchange system, passive solar greenhouses absorb and store the warmth from the sun during the day to keep it warm at night. Attached solar greenhouses are very popular with homeowners. These are lean to greenhouse structures attached to homes that can also help provide some extra heat in the home. The extra cost of materials and work involved in setting up a passive solar greenhouse will be returned many times over in increased plant and vegetable production.