The development of practical solar heating and cooling systems has been a principal objective of the Solar Energy Applications Laboratory at Colorado State University since its beginning in November, 1972. The first solar heated and cooled experimental building was constructed at-CSU in 1974 as a major effort to develop a liquid-based solar system that would be suitable for use in residential and light commercial buildings anywhere in the United States. As a consequence of this early work practical designs have been produced, performances have been measured, and performance prediction methods have been checked.

There are currently four solar houses in the Solar Village at Colorado State University as shown in Fig. l. They are devoted to experimental development, testing and evaluation of solar heating and cooling systems. Additionally, there are separate facilities to test collectors, develop system controls, and investigate thermal storage devices preceding their inclusion and installation in experimental systems.

Solar House II, second from the right in the figure, is presently devoted to the development of air systems.' Solar House III, extreme right in the figure, and Solar House II were constructed in 1975.' Solar House III has' been utilized to test, develop and evaluate a liquid based evacuated tube collector system, and most recently was equipped with a "state-of-the-art" flat-plate liquid-heating' system. The' performance results from Solar Houses I, II and III are directly comparable because the buildings are similar in construction and the environmental conditions are identical for all the systems at any one time.

Solar House IV shown on the left in the photograph is a combination greenhouse/residence building which has been devoted to the development of hybrid passive/active systems. Emphasis in Solar House IV has been on heating of the greenhouse, of residential space and of plant beds. It has provided performance data not available elsewhere prior to systematic testing. The facility affords an excellent opportunity to develop hybrid solar systems using the passive heat gain in the greenhouse to augment solar heat provided by an active system.

Solar House, I, second from the left in the figure, began operation in August 1974. The experimental data from CSU Solar House I was, for many years, the only detailed data on solar heating system performance available and was used extensively.

This paper provides and analyses much of the data collected from these four houses.