The performance of solar water heating systems at three homes in cold climates is reported. The house located in Colorado utilized the solar thermal system for space heating and domestic hot water and produced savings of approximately 105 therms of natural gas and $93 over the course of the first year of operation. The solar fraction ranged between 7% in the winter and 100% in the summer months. A prototype house in Wisconsin exhibited solar domestic hot water savings of approximately 86 therms of natural gas and $58 for 10 months of operation, with solar fractions ranging between 16% in the winter to 93% in the summer. The solar domestic hot water system installed at a house built in Massachusetts offset 72 gallons of heating oil/biodiesel fuel worth $133 by offering solar fractions between 26% and 87%. Installation deviations from the designs which affected performance were experienced in two of the homes. In one house, the solar loop heat exchanger within the storage tank was piped backwards, discouraging tank stratification. In another case, a tempering valve was installed between the storage tank and the tankless water heater, forcing the heater to fire, even when the solar storage tank had the capability of supplying the draw of hot water. These issues and their solutions are discussed. These cases are used to highlight some of the challenges of incorporating solar thermal systems into production building.
