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Warmfloor versus hydronic heating set in gypcrete or Maxxon Therma-flor?

I'm an architect in WA. A client is building a new home in Eureka, CA. I had specified hydronic radiant heating set in a Maxxon Therma-Floor (similar to gypcrete) base. There is no supplier in the Eureka area. Apparently it comes out of Santa Rosa or Sacramento. The owner and contractor are now thinking about using Warmfloor (electric radiant heating). I have heard that the heat fluctuates more with Warmfloor because there is no mass. Does anyone have experience with Warmfloor? or any suggestions about gypcrete supplier/installer for the Eureka area?

Asked by Karla Forsbeck
Posted Fri, 05/16/2014 - 18:38

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3 Answers

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Karla,
I'm no fan of hydronically heated floors, but hydronic heating systems almost always make more sense than electric-resistance systems like Warmfloor. Unless your electricity rates are quite low, or your building envelope is extremely well insulated and tight, or the house has a very large PV system, heating with electric resistance elements usually condemns the homeowner to high energy bills.

Answered by Martin Holladay, GBA Advisor
Posted Sat, 05/17/2014 - 06:50

2.
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WarmBoard (tm) or tubing under a wooden subfloor using extruded aluminum sections to get the heat out of the tubing & into the subfloor can work at condensing water temperatures for high efficiency using condensing boilers, just like the gypsum & lightweight concrete solutions. It's more expensive to install than resistive electric mats, but quite a bit cheaper to run.

There notion that the floor needs the thermal mass of the gypsum-concrete to avoid temperature fluctuations is not well founded. Systems that don't have aluminum to even out the floor temps with distance run at higher water temps, and have distinct "striping" of temperature across the floor, but that doesn't mean the temperatures fluctuate. In a well designed system with proper controls the temperature at any given point in the floor won't change rapidly with time, but with high-temp staple-up radiant systems the temps will vary by proximity to the tubing. But with lower temp systems using aluminum spreaders that striping effect is fairly minimal.

WarmBoard is installed above the sub-floor, and is quite responsive- can even be used with set-back thermostats (unlike Gypcrete, etc.), whereas systems using aluminum plates or extrusions under the subfloor are slower to respond, and like the high mass systems, better run in "set & forget" mode. They also take somewhat higher water temps than WarmBoard or Gypcrete, but at WA code-min construction heat loads would still be able to run at water temps suitable for condensing boilers even at the 99% design condition.

Answered by Dana Dorsett
Posted Mon, 05/19/2014 - 13:46

3.
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Karla ,

Dana is correct . Mass , as earlier thought should not be in the floor . Systems using above sub floor boards with aluminum or even better graphite are very responsive , require lower water temps , and can utilize setback if desired . In the correct application or where the heat loss of the home allows you may not even require a separate appliance for space heating . Remember , the closer the spacing the lower the supply water temps , the more efficient the equipment will operate (condensing) . Warmboard is hands down the best 12" on center product there is , I prefer and use Sunboard panel with the graphite covering , the heat spread is more even , it is more economical , and the spacing at 8" on center allows me to use lower SWTs maximizing efficiency of whatever source is being used .

Answered by Richard McGrath
Posted Tue, 05/20/2014 - 08:58

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