Imagine 700-foot-long circuits of 1/2-inch PEX tubing laced back and forth through a series of holes in the floor joists. No heat transfer plates are present. Along the bottom of the floor joists is a layer of bubble foil insulation.
Consider that this installation is in upper Minnesota where design temperatures approach –40 degrees F and winds often come straight down from the Arctic.
Do you envision a barefooted family circled around a board game on their toasty floor, like you’ve seen in sales literature for radiant floor heating?
If you’re an experienced hydronics professional, you’re more likely picturing that family wrapped in blankets, scarves and hats while one of the parents angrily complains to the heating installer on the phone. A few weeks later, you might even envision a litigation process getting underway. Another hapless attempt to bend the laws of physics has soured a homeowner, enriched an attorney and convinced an apathetic installer to stay away from future radiant heating installations.
But wait! I’ve actually been told there’s at least one installation fitting this technical description that performs just fine for its owner.
How can this be?
Perhaps the house is super-insulated and almost hermetically sealed so its design heating load is a scant 5 Btu/hr/square foot. Maybe the owner is “warm-blooded,” and an indoor temperature of 55 degrees F is just fine when it’s –40 degrees F outside. Or perhaps there’s an area up in northern Minnesota where physics just doesn’t apply.
Short of these possibilities, all I can say is, “lucky or liar,” because this installation method is about as far from recommended practice as it gets.
Discovery Of The CenturyHave you heard that all those Ph.D.s in the research departments at Dow, Owens Corning and Certainteed have been asleep at the wheel? Apparently they all missed the discovery of a foam-based insulation material that yields an R-value of 40 degrees F•hr•ft2/Btu, with a thickness of only one inch!
How do I know this? The person who discovered this miracle insulation product told me about it.
Think of the implications: You could build a super-insulated house with walls and ceilings that only have one inch of this material. Assuming 10 percent of the walls in a 1,500-square-foot house were R-3 windows, and the air leakage was 0.3 air changes per hour, this house would lose less than 15,000 Btu/hr when it’s 0 degrees F outside. You could keep it comfortable with a couple small electric space heaters from Wal-Mart.
This new miracle insulation makes typical extruded polystyrene, with an R-value of about 5.4 per inch of thickness, look pathetic. How could all those smart people, working for those multibillion dollar world-wide companies, have missed this discovery - and missed it by almost 800 percent? Perhaps the person who discovered this miracle product got very lucky. Or perhaps there’s another explanation…
During our conversation, I told the purveyor of this miracle insulation that when my seal goes on a set of plans, I’m responsible for the performance of all the materials and methods specified. I asked him to send me third-party testing results for the product to ensure that it performs as claimed. He said he would. I’m still waiting.
A Fool And His Money Are Soon PartedDuring my years in the heating industry, I’ve heard some pretty interesting claims, some of which challenge the limits of reality and just plain defy explanation. Some of these claims are probably entertaining to those with experience and knowledge of the fundamental physics that’s always at play. Unfortunately, these claims often lead to sales to those that choose not to, or simply don’t have the background to, scrutinize them. Disappointment soon follows. At that point, the vendor either insists the product was not properly applied or has simply moved on to the next miracle.
Your customers will seldom challenge the decisions you make about the methods and materials used in their heating systems. They simply expect those choices to provide years of reliable and efficient operation, and don’t care about any further details. They trust you, as a professional, to make the right decisions.
Those decisions usually involve thousands or even hundreds of thousands of dollars worth of materials and labor. Some of those chosen materials might literally be set in (or under) concrete, and thus are essentially irreversible.
The best defense is a good offense. When you come across a material or method that’s drastically different from current practice, it pays to ask questions and understand how the new material or method performs as well as it does within the unwavering laws of physics. Ignorance of those laws is no excuse. There is no such thing as “inexplicably great performance.”
Ask for third-party test results on new products or installation methods. Get them and read them. Ask those promoting new methods or materials for references that you can contact to verify performance claims. Manufacturers of legitimate products are happy to support your inquiries with third-party testing results, as well as listings of the standards they meet. If instead you decide to take every vendor at his word, be sure to check your general liability insurance and prepare to go it alone should actual performance fall well short of claims.
One of the best ways to gain knowledge on materials and methods used for modern hydronic systems is to attend an industry conference, like the Radiant Panel Association’s “REXperience” event coming this May in Utica, N.Y. In addition to attending seminars on specific topics, you can listen in as often-controversial issues are debated by your peers in the hallways and lobbies. You’ll have plenty of opportunity for second opinions from people who’ve cleared hurdles you may not yet have encountered.
By scrutinizing products and installation methods, you’re helping yourself as well as the hydronics industry maintain standards that will ensure a vibrant future.
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