BY JOHN SIEGENTHALER
With systems dating back into the 1800s, hydronic heating has been around a long time. As with many technologies, a modern hydronic heating system bears little resemblance to one based on the earliest design techniques and hardware. Imagine explaining the concept of a circulator to a design engineer from 1900 who might only know of electricity as something a few scientists experiment with. Think about convincing an engineer of that era that pipes capable of lasting well over 100 years could be made of materials derived from oil.
Hydronic systems were the “norm” in many buildings prior to the availability of central cooling systems, which began entering the U.S. market in the late 1950s. Central cooling was indeed a “game changer” for the U.S. thermal comfort market. It shifted focus to forced air distribution systems, which could deliver that highly anticipated cool/dry air in summer, as well as heated air in winter.
The compromises associated with forced air heating, including air temperature stratification, dirt accumulating in ducting and low interior relative humidity due to increased air leakage were tolerated because come summer, the cool/dry air delivered by those forced air systems was considered a “godsend.”
When central cooling first became available, hydronic heating systems were almost always supplied by boilers burning fossil fuels. Most were designed around what we now consider to be “high temperature” heat emitters, such as cast-iron radiator, cast-iron baseboard, wall convectors and eventually fin-tube baseboard. The radiant panel heating market slowly evolved from its beginning with iron-based pipe to copper tubing, which, in the years following WWII, was considered a major advancement in piping technology.
Still, the allure of central cooling, driven by the marketing capabilities of major corporations and the desire of Americans to have the appurtenances of “modern” homes, allowed forced air systems to continue to gain market share over hydronic systems.
By the late 1970s, when I got my first job that exposed me to hydronics, the radiant panel heating market was almost extinct. I even remember being told by my first boss, a sincere man who helped pioneer the use of copper tubing in radiant heating systems, to “forget about radiant heating, it’s dead, it’s gone.”
Who would have known that within about four years of that statement, the first Wirsbo PEX tubing would appear on the North American market to slowly, but surely, resurrect the hydronic radiant panel heating market.
Much of this interest has been stoked by government and utility programs aimed at reducing, and in some cases, eliminating the use of fossil fuels heating buildings.
Fortunately, most of my career has been spent enjoying the benefits afforded by a growing market for hydronic heating. Boilers have evolved from 500-pound units connected to masonry chimneys to wall-hung cabinets that automatically connect and converse with wireless communication devices located just about anywhere in the world. Circulators have changed from those using external motors and spring-loaded couplings to small ECM-based devices that think — to some extent — for themselves. I could go on about changes in other devices such as thermostats, tubing joining methods, and so forth, but I’m sure you get the point.
Still, for decades, hydronics technology has suffered from a major limitation. Simply put: Boilers can’t provide cooling.
I’ve witnessed situations where potential customers who adored the expectations of superior comfort, silent operation and elimination of floor registers, reluctantly gave up on installing hydronic systems because they couldn’t provide cooling. They would not accept the fallback suggestion that a different installer could provide a totally separate cooling system, especially when that option would add significant cost over an already premium-priced hydronic radiant panel heating system.
There’s little doubt that the (perceived) inability of residential hydronic systems to provide cooling has been a major factor in limiting their market share to single digits over several decades.
Future historians will have no trouble establishing a correlation between hydronics technology and boilers of all sorts. The hydronic heating market has been, and continues to be dominated by boilers that produce hot water by combusting a fuel.
However, over the last few years, several trends suggest that the future of hydronics technology may not be dominated by combustion-based boilers. Electrically-powered heat pumps, in all their varied configurations, are quickly establishing a new normal for supplying heat to buildings.
Much of this interest has been stoked by government and utility programs aimed at reducing, and in some cases, eliminating the use of fossil fuels heating buildings. There’s also increasing consumer demands for carbon reduction strategies. The increasing aggregate capacity of utility-scale solar and wind-generated electricity in North America is also contributing toward this transformation.
If you’re not convinced, I suggest downloading a copy of the publication “Advancing Toward 100 Percent,” from the Clean Energy States Alliance. It’s a free downloadable PDF. This publication is not a propaganda piece. It’s a compilation of the energy policies that many states are implementing, which, whether you agree with the underlying motivations or not, will be a major influence in shaping the future market for hydronics technology.
Nearly all heat pumps suitable as hydronic heat sources can also provide chilled water for cooling.
Collectively, these trends and energy roadmaps represent one of the biggest opportunities the hydronics market has been presented in decades. Not necessarily because of fuel switching, but because nearly all heat pumps suitable as hydronic heat sources can also provide chilled water for cooling.
Hydronic professionals need to capitalize on this. The hardware for doing so is already on the market. Air handlers with chilled water coils, console fan-coils with condensate pans and even radiant panel hardware in combination with appropriate controls, can be applied as the means of converting chilled water into excellent cooling and dehumidification.
Heat pumps enable a mechanical contractor to provide answers to questions like “I really want to use radiant floor heating in my new home, but what do I do about cooling?” They also enable that contractor to provide a “total comfort (and DHW) solution,” and take sole responsibility for the system, profitting from providing additional materials and labor on each sale.
I anticipate that one of the biggest challenges in growing the small-scale chilled water cooling market is understanding the importance of insulating and vapor sealing all piping components conveying chilled water. Although this sounds like a “no-brainer,” it’s anything but. Most hydronic heating systems in North America are still installed without insulation on pipes and piping components. The justification is usually that the piping is in conditioned space, and thus, heat loss from it is contributing to the building’s heating load. Installers who carry this “tradition” into the chilled water cooling market will quickly learn a costly lesson. Moisture-laden air is unforgiving to improperly selected insulation or poor workmanship. If that air contacts any surface below the dewpoint temperature, condensation will occur. Puddles, stains and rusty surfaces will follow.
Although there are plenty of pipe insulation materials available for chilled water systems, the same cannot be said for other basic hydronic components. Examples include circulator volutes, air and dirt separators, buffer tanks, isolation flanges and even basic valves. In most cases, the current “solution” is to wrap these components with elastomeric foam tape. If properly done, this works, but it’s time consuming and not very aesthetically pleasing. Manufacturers need to step up with pre-formed insulation shells for their components, along with details and products that allow simple seamless transitions between these components and adjoining pipe insulation.
If you want to avail yourself of the growing market for small-scale hydronic cooling I suggest the following:
Hydronic pros who choose to read the “tea leaves” regarding heat pumps, and act smartly on that information, will surely profit. Opportunities for integrating heat pumps into hydronic systems are already occurring in many areas of the U.S. Demand will increase as state electrification goals continue to shape the market.
The movement toward “beneficial electrification” is perhaps one of the biggest opportunities set before the North American hydronics market in decades. With all due respect to product development, this opportunity is more consequential than next year’s new offerings for boilers, Wi-Fi thermostats or press tools.
It’s also an opportunity that comes with many “advocates,” such as architects, low-energy home builders, Solar PV installers, utility reps, regional energy planners, environmental proponents and yes — even politicians. The words “heat pump” will grab their attention, setting up the opportunity for you to explain how hydronics technology completes the comfort part of the offering. The potential end results from combining heat pumps with hydronics far exceed those attainable using air-to-air heat pumps, mini-splits or VRF systems.
A final bit of counsel: Please view this confluence of market trends without personal or political bias. You may or may not agree with the social or political spin associated with these trends. Be that as it may, you should recognize the exceptional opportunity to expand your company’s profit potential, and “evangelize” your passion for hydronics to a much broader and highly receptive audience.
Photo courtesy of John Siegenthaler.
John Siegenthaler, P.E., is a consulting engineer and principal of Appropriate Designs in Holland Patent, New York. In partnership with HeatSpring, he has developed several online courses that provide in-depth, design-level training in modern hydronics systems, air-to-water heat pumps and biomass boiler systems. Additional information and resources for hydronic system design are available on Siegenthaler’s website, www.hydronicpros.com.