Solar combisystem |


When we were approached about using solar to reduce the propane demand for a proposed off-grid home in Monroe, there were several options at our disposal. Our owner, Vaughan Woodruff, has developed a course with Heatspring called Solar Approaches to Radiant Heating and worked on several types of solar combisystems – systems that provide domestic water heating and radiant heating – in Montana before moving back home to Maine.

There are good ways to utilize solar heating for supplementing the heating demands of a home, and there are numerous examples of doing it poorly. Ultimately, an effective solar combisystem requires simplicity in its piping and control strategies. Too many poorly installed systems have taken custom approaches that increase the complexity significantly. Many simply do not accomplish the goal of effectively using the sun’s energy to provide comfort and minimize the consumption of fossil fuels.

We approach solar combisystems with an eye toward Europe, where these systems are common. A high-efficiency off-grid home is a great application for a solar combisystem, as it provides greater autonomy for the owner, provides baseline heat when the owner is away, and reduces dependency on fuels with high price volatility.

During the consultation process, we explored several different types of systems that use buffer tanks to integrate the solar, propane, and radiant distribution in a simple manner. After discussing some of the space restrictions, the design of the house, and the overall project budget, we ultimately selected the use of the HTP Versa-Hydro Solar combination appliance.

HTP’s design integrates a condensing propane boiler, storage tank, and solar heat exchanger in a single engineered product. The design allows for simple, isolated controls for the solar heating portion of the system, the propane input to the system, and the distribution of radiant heat and domestic hot water.

Learn more about this home’s off-grid solar photovoltaic (PV) system here.