Misconceptions about hydronics, radiant heating

Sept. 5, 2014
I want to stop and address some radiant/hydronics myths That hydronics are too expensive That hydronic radiant floors won’t work in a super insulated homes That you can’t justify installing a boiler in a super insulated Passiv Haus home That hydronic systems are too complicated for most technicians That plumbers aren’t qualified to do hydronic heating That radiant cooling doesn’t work in humid climates  
Every once in a great while, it pays to stop and look backward to see where you have been so you can figure out where you are going and make certain you have a plan to complete your journey. It also pays to read the signs along the way, even though some of them may be conflicted. Such is the case with my journey in hydronics over the past 30-plus years, especially as it pertains to radiant and hydronics. I want to stop and address some of these myths so moving forwardwe have a clear view.

Hydronics are too expensive: I used to hear that complaint all of the time. It usually came from the mouths of building contractors who really had no idea of the comfort that our hydronic systems could deliver, and really all that they were looking at was the dollar cost per square foot, not the benefits of comfort and affordable efficiency that are unmatched by any other system on the market.

The few smart general contractors I used to work for understood the value of hydronics and offered it as an alternative to their customers as an add on. They were also very profitable and weren’t really just looking for the lowest dollar cost per square foot for a “heating system.” I am also aware of one of our members who is turning out radiant ceiling heating and cooling systems in the Southern California market for a cost equal to that of forced air, except that the comfort conditions are incomparable, and cost of operation significantly less. It can be done, but we have to take our focus off of warm floors and put it on radiant comfort.

Hydronic radiant floors won’t work in a super insulated home: This rumor has more truth to it, but again is a misconception. The larger the energy emitting surface, and the lower the energy loads (heating or cooling) then the lower the surface temperature will be. This doesn’t mean a person can’t heat their super insulated Passiv Haus with hydronics; it just means that the installing contractor shouldn’t push the concept of “warm floors", but instead should look to alternative emitting surfaces like ceilings, walls and bathroom floors, and sell the concept of “radiant comfort” instead of “warm floors". If ceilings are chosen as the emitter of choice, it will require less material and labor to make the system work, and the consumer will be much more comfortable using a radiantly heated and cooled building than they will using any other method of delivery, which leads us to the next rumor…

You can’t justify installing a boiler in a super insulated Passiv Haushome: This statement would be true if the boiler were only going to be providing space heating. What about the production of domestic hot water (DHW)? Having a super insulated home does nothing to address this major energy need. If the appliance is set up correctly with a reverse indirect, it will work perfectly for providing ultra high efficiency domestic hot water production and also provide a nice buffer tank and space heating system.

In fact, the numbers I have seen tell me that there isn’t a boiler with an output small enough to satisfy the heating demands of these super insulated homes without creating short cycling conditions. The use of the reverse indirect tank as a buffer tank for space heating and DHW production kills two birds with one stone, and the modulating condensing heat source stays in the sweet mode of condensing even when it’s producing DHW.

Hydronic systems are too complicated for most technicians to work on: The fact is we have built some systems that make the technology used on the International Space station look weak in comparison to the technology used in our comfort systems. But that doesn’t preclude the possibility of simplifying these systems. It all comes down to a competent design and installation.

 A simple dual load heat source as previously addressed, coupled with a single state of the art variable speed circulator, coupled with an appropriately sized emitter panel, tied to readily available modulating non- electric thermostatic control valves, will provide the end users with the perfect high efficiency radiant comfort system that can deliver the highest degree of comfort and efficiency known to mankind. And with the recent introduction of modulating compressors, it is entirely possible to provide a modulating cooling system as well.It’s just heat.What’s the big difference? The big difference, if you will, is that radiant heating and cooling affect the Mean Radiant Temperature (MRT) of a given building. For those who don’t know, the MRT is the number one factor that influences human comfort. No other conventional system can make this claim. It directly addresses the primary means of delivering excellent human comfort by addressing the MRT, and in the case of heating, does so without moving a lot of air. This is one of those things that must be experienced in order to understand its value, and once it is experienced firsthand, the true meaning of radiant comfort becomes priceless.  We are working towards having some “Experiential Demonstration Centers” whereby our members and their customers can go and actually experience radiant comfort first hand. Stay tuned for more information.

Plumbers aren’t qualified to do hydronic heating: Now, if this is true, I and many of our members are a huge anomaly.  I started out as a residential plumber and ended up doing nothing but hydronics. It is true that the skill sets required are essentially the same as those of a pipe fitter, but other than requiring additional training above and beyond the requirements of conventional plumbing, there is absolutely no reason a properly qualified and properly trained and licensed plumber has to limit their trade to the potable water and drain waste and vent sides of a given building.

In fact, if you are in the plumbing trade and are not offering hydronics as a part of your services, you are leaving a lot of potential revenue on the table to your competition. The RPA has many technical training opportunities available to qualified contractors to show them how to do these installations right. It requires a time commitment, but the rewards well outweigh the risks and costs associated with getting proper training.

Radiant cooling doesn’t work in humid climates:  This rumor couldn’t be further from the truth. Yes, it will require the movement of air, but the required movement of air in order to control the relative humidity and dew point are a minor fraction of the air movement required to address both the sensible and latent energy needs of a given building. It does require a proper load calculation and a proper system design and installation, but again, any system that is worth its salt also requires these commitments to ensure proper, efficient delivery of good human comfort.

Many major PEX tubing manufacturers are now offering radiant cooling as a part of their offering. If you haven’t looked into it yet, you need to do so soon before your competition does, and makes you look like a Johnny Come Lately. And don’t dwell on the production of condensation. They have it well under control.

If you are not a member of the RPA yet, you should check us out at www.radiantprofessionalsalliance.org. Look around the  web site and see who our members are. This is one of the largest brain trust of hydronic experts in the world, and we are here to help you grow radiant and hydronics. Joins us, won’t you?

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