Part of running any business is looking ahead and trying to read the “tea leaves” that are relevant to that business. For those involved in hydronic technology, one of the largest tea leaves is energy. What fuels will be powering our hydronic heating and cooling systems a decade from now and beyond?  

Political, environmental and social forces are playing increasingly influential roles in shaping the answer to that question. State and federal governments spend tens of billions of dollars every year influencing the course of energy markets. So do utilities, advocacy groups and even some faith organizations.

Whether you agree or disagree with the underlying logic and statistics, the global attitude toward fossil fuels is souring. You may support this, or view it with disdain.  Either way, as a comfort professional you’re going to have to deal with it.

From what I can gather, the future of energy for heating and cooling buildings is pretty much focused around one word — electricity. 

This has some pretty strong implications. Let me infer one of them: If you plan to be a professional in the North American hydronics market ten years from now, you better know how to deal with heat pumps.

According to Building Design + Construction magazine, the market for net zero buildings in North America is on course to grow at an annual rate of over 38% between 2014 and 2035. Electrically powered heat pumps, in one form or another, are already being used for heating and cooling in most existing net-zero buildings, and it certainly appears that this trend will continue.  

Will the North American hydronics industry cede this developing opportunity to ductless mini-split heat pumps in the residential sector, or cease the opportunity to finally expand beyond a single digit market share? Will the letters VRF replace H2O in the commercial sector, or will the indisputable advantages of hydronic distribution systems prevail against the requisite miles of ACR copper tubing and hundreds of pounds of refrigerant that’s one ruptured joint away from a hazmat emergency?



Modern hydronic technology and heat pumps are a great combination. Both water-to-water heat pumps connected to ground sources and cold climate air-to-water heat pumps make excellent heat sources for hydronic heating distribution systems that can operate on supply water temperature no higher than 120° F.  

Beyond this match up for heating is the ability of water-to-water and air-to-water heat pumps to produce chilled water for cooling. That’s a unique benefit that no boiler can match. It’s also an answer to the long standing (and very legitimate) question from prospective customers: “What do I do about cooling?”  

That query, followed by a realistic and honest answer from someone who only offers boilers, has undoubtedly derailed many decisions to use hydronics heating.  

By combining a hydronic heat pump with other off-the-shelf hardware, it’s possible to create customized hydronic cooling systems. Perhaps the cooled and dehumidified air will be delivered to the building through a single chilled water air handler. Another option is zoned console fan-coils, high wall fan-coils or some combination of these terminal units. With proper design and control, radiant panels can assume the majority of a sensible cooling load in combination with chilled water coil in a small air handler for dehumidification, ventilation and any remaining sensible cooling.

The system concept is straight forward, during cooling mode the heat pump maintains a buffer tank within a working temperature range such as 40° to 60°.  When a zone calls for cooling, the chilled water is routed from the tank to the terminal unit in that zone by a circulator or through a zone valve. The coil in the terminal unit cools and dehumidifies the air passing through it. Condensate from the coil is captured by a drip pan and routed to a suitable drain.



Although any competent hydronic pro could assemble the hardware needed for a small chilled water cooling system, there is one “Achilles heel” that’s always waiting to spoil the party: The unavoidable fact that dehumidification will occur on any surface that’s below the dewpoint temperature of the surrounding air. That’s a reality that often gets learned the hard way, especially by those who’ve spent decades installing uninsulated piping for hydronic heating. 

If you don’t believe me, try pumping 45° water through bare copper tubing on a mildly humid day when the surrounding air has a dewpoint of 65° or higher. You won’t have to wait long to see the results. 

Beads of condensate will form on metal piping, valves and other components in less than five minutes. In five more minutes, those beads will be large enough to drip onto whatever is below them. 

If the bare piping happens to be above a drywall ceiling, you might have to wait a bit longer to see the results, but I guarantee they will eventually get your attention, and probably lead to a claim against your liability insurance. 

The bottom line: If you’re going to install piping systems for chilled water, you have to take insulation and vapor sealing seriously. If you get sloppy, even on small seemingly obscure details, those H2O molecules floating in the air will call you out.



This leads me to a problem that needs a solution. The volutes of small circulators used in chilled water cooling systems are very hard to properly (and neatly) insulate with the materials currently on the market.  

In North America, a few commercial size circulators are available with form-fitting insulation shells.  However, I only know of one such product for a small residential/light commercial circulator. Without an insulated and vapor sealed volute, most currently available circulator volutes are going to be coated with oxidation within a few hours of chilled water operation. Figure 1 offers proof. And before anyone starts conjecturing, I can assure you that this problem is not specific to any specific brand, it can happen on all of them.

Siegenthaler - Figure 1

Beyond the circulator’s volute are the steel components used on the isolation flanges. Although these parts are usually zinc-plated, it’s just a matter of time until the presence of condensate leads to oxidation. It’s plainly evident in Figure 1.

One “lackluster” option is to painstakingly wrap pieces of adhesive-backed elastomeric foam tape around the multiple contours of a circulator volute. Then keep your fingers crossed that the adhesive keeps that foam in place. This, in my option, is a messy and time consuming approach that looks unprofessional and is not likely to be accepted in the field.

Our industry needs a better way to insulate circulator volutes. Maybe it’s a series of insulation shells that are precisely shaped for specific circulators. These shells are split down the middle and easily fit together after the circulator is installed. The R-value of the insulation shell doesn’t need to be very high.  A nominal R-3 (°F•hr•ft2/Btu) rating would be sufficient for most applications.  

For chilled water applications, what’s arguably more important than R-value is the continuity of the insulation and vapor barrier around all small details on the volute and the connected piping. There should be a complete air seal at all edges of the shell. There should also be an air-tight and vapor-tight transition from the volute insulation, across the isolation flanges, and onto the adjoining pipe. The guiding principle is simple — if air can reach the cold surface, condensation will form.

Another possibility might be a hollow plastic shell that again easily snaps together around the volute and flanges of an installed circulator. This shell then gets filled with an expanding foam that finds its way around all the nooks and crannies. Perhaps the volute would first be coated with a release agent so that the foam would easily pull away if the circulator needs to be replaced.

These insulation systems would not cover the motor or electrical portions of the circulators. Those areas typically generate sufficient heat to prevent condensate formation. If covered with insulation these portions of a circulator would likely cause overheating if and when hot fluids passed through the circulator.



Circulator manufacturers — please consider how your small circulators will be used in upcoming chilled water cooling applications. The industry needs a simple, reliable solution to prevent surface condensation. 

If past trends on how novel hydronic components have influenced the market are an indicator, manufacturers who get dependable solutions into the field early are likely become preferred suppliers.