A hybrid passive/active solar heating system, featuring a passive air thermosiphon loop, is described. Heated air is supplied to a rock storage bin, coupled with blower-driven air distribution to the house. The house, of 246 m/sup 2/ (2650 ft/sup 2/) heated area and located in Santa Fe, New Mexico, also includes a greenhouse located under the planar collector array. Architectural features and construction details of the house, the solar collector, storage, and distribution system are presented. Representative results of three months of monitoring by the Los Alamos Scientific Laboratory of collector, rock bin, and greenhouse temperatures, as well as outside ambient temperature and insolation, are reported and discussed. Data recorded hourly since the system was placed in operation in early February 1978, show temperatures in the rock bin in excess of 71/sup 0/C (160/sup 0/F) and in the collector absorber mesh in excess of 93/sup 0/C (200/sup 0/F). Delivery temperatures from the charged bin, without auxiliary boost, range from 38 to 54/sup 0/C (100 to 130/sup 0/F).