When Does an Air-to-Water Heat Pump Make Sense? – GreenBuildingAdvisor

Product Guide

GBA connects with HVAC and building pros to dissect the virtues and drawbacks of A2W systems

In our continued search for the most economically and energy-efficient equipment to put into our homes, U.S. consumers seem to be paying more attention to air-to-water (A2W) heat pumps. While not new to other parts of the world (they are the most popular heating systems for new buildings in Germany), a growing cast of HVAC manufacturers now offer A2W systems (aka hydronic heat pumps) for North American markets, suggesting that increased adoption is inevitable. But in place of what, exactly? And what are the external factors that inform when installing A2W heat pumps is the efficient choice vs. an extraneous addition?

The short answers to the above questions are ground-source heating systems, and lower outdoor temperatures coupled with lower water temperatures. But that only scratches the proverbial surface of what makes these heat pumps tick. Besides, GBA contributing editor (and seasoned HVAC installer) Jon Harrod recently wrote a thorough rundown of A2W systems’ numerous benefits, as well as how they operate, right down to their use of refrigerants with lower global-warming potential. It’s about as detailed and insightful a piece you’ll find on hydronic heat pumps to date, so I’ll forgo retreading much of the ground that Harrod has already covered.

I do, however, want to get into the weeds on why some specialists in the homebuilding field aren’t 100% sold on A2W systems. One of the more obvious drawbacks is the combined cost of equipment and labor; another is “all the additional components that go into any hydronic system: pumps, piping, expansion tanks, controls, etc.,” Harrod observes. There really is no way around those hurdles when compared to less cumbersome options like air-source heat pumps or even a traditional furnace. But weighing the severity of each drawback and determining whether A2W…