From day one we wanted to have hydronic floor heating, our architect had used Warmboard before and seemed like a no-brainer over other approaches. 1 1/8″ plywood sub-floor with channels for 1/2″ PEX and a thin layer of aluminum on the top to her spread heat evenly. Looks like Warmboard offers a turnkey package now that includes heat loss analysis and an appropriate boiler, but we just got the system design, panels, tubing, and manifolds from them (through the architect as part of their package). Then our plumber helped us pick out a boiler and installed that and the tubing and manifolds and controls.
I think a fair number of people don’t bother with zones for hydronic heating, and with high efficiency condensing boilers they are most efficient when you don’t use a thermostat and just make your adjustments at the boiler, pretty much set it and forget it. But we like sleeping in a cool bedroom, having a toasty floor in the bathroom, and being able to dial back areas of the house we are not using (just two of us in the home), so we opted for five zones with thermostats, (1) master bedroom, (2) master bath, (3) living area, (4) upstairs bedrooms, and (5) upstairs loft. Warmboard produces a really nice set of plans and instructions that show the panel layout and also the tubing layout, highlighting where custom grooves/channels will have to be cut with a router (they provide templates). There was a little back and forth with Warmboard re zones, and also a panel layout adjustment to make sure channels were running perpendicular to joists in one room (1 1/8″ is more like 1/2″ at channels, so I don’t think you want those running parallel to floor joists).
Despite the fact that the architect was familiar with Warmboard there were a few issues with their installation of the subfloor panels. First, they used the plans provided by Warmboard as a general guide, but did not follow them closely, resulting in the need for additional routing of channels (adding cost and reducing effectiveness of the aluminum layer) and creating a couple of “cold spots.” Perhaps following an outdated set of plans they also installed a few panels with channels running parallel to the floor joists, I caught this and asked that they be pulled up and re-done. That required ordering some additional panels, which took some time to come and interrupted/complicated further work while we waited for those to come in. Finally, the installer ignored the Warmboard guidance that a 1/8″ gap should be left between the ends of the panels, the reason for which became clear later on as panels expanded and caused some buckling that did not subside. We still have some very noticeable high spots in the floors.
Our construction manager was worried about hydronic (PEX) tubing getting damaged during installation, so we completed the interior (blown closed cell) insulation before tubing (a little under 3000′) was installed. After installation and testing we insulated under the main level, encasing the tubing below the subfloor in closed cell foam. We then protected the tubing by covering the floors with the cheapest 1/4″ 4×8 material we could find.
For a boiler we selected a German engineered and made wall mounted Viessman Vitodens 200-W B2HB 57 (57 for roughly 57kW I think, which is about 200 kBTU, we did not do any formal heat loss calculations, I suspect it was overkill going with the largest version of this boiler). The boiler provides hot water to the hydronic heating system through a Viessman mixing valve and three circulators connected to three Warmboard manifolds. The manifolds seem quite nice, though the site glasses for flow rate adjustments get hard/impossible to see through pretty quickly. Each loop has a Stellantrieb 24 volt actuator that is controlled by one of two Taco ZVC403s, which are in turn controlled by five Nest thermostats (I failed to install wiring for these and construction manager/installer didn’t catch this, so we had to run wires after drywall was up, which was a pain).
As I mentioned before, the boiler could control everything if we only wanted to have one heating zone, with that approach you would not need the thermostats or Tacos or actuators, and you could still dial some areas of the home up or down by adjusting loop flow rates. The boiler has an outdoor temperature sensor and you tweak slop and offset to adjust a “heating curve” that determines how hot the water delivered to the hydronic heating system is. Each manifold has temperature gauges at input and output, so you can see how much the temperature is dropping, which indicates how much heat is being left in the area being heated. The installer did initially make a mistake with circulators for the hydronic system, with the manifolds having actuators that are opening and closing the circulators are deadheading, in some cases frequently/for extended periods of time. The solution was to install circulators that are designed to handle deadheading, in our case they used Grundfos ALPHA1s. I ordered a Vitoconnect 100 from a local supplier and installed it so I can monitor and control the boiler remotely (installer did not know much about Viessman equipment, a Viessman tech helped with some things, but I don’t think he really knew about remote monitoring/control either).
The boiler also feeds an 300 liter (79 gallon) Viessman Vitocell 100-V indirect water heater. The construction manager floated the idea of tankless water heaters, but then you need to plumb gas to those, where are you going to put them, and they are expensive. For me was simpler to just have an indirect tank that is large enough to fill up a bathtub. Indirect tanks are simple, super low maintenance, and last longer than a gas fired water heater, and are not too expensive (though ours was made in France).
There was a little bit of a learning curve with this equipment. Took me awhile to figure out that the hydronic system shuts down (power to circulators is cut) when the DHW loop kicks in. And when it is warm enough outside the power the the hydronic system circulators is shut off. The settings for the boiler are pretty extensive, I am sure all of this can be controlled/changed.
Then we had a couple of leaks that were bad enough to cause damage to the sheet rock in the garage area below the mechanical room. First leak was coming from the condensate drain line at the bottom of the boiler, and drove me crazy trying to figure out what was causing it, took lots of photos, took the boiler apart, calls to Viessman, etc. Turns out the problem was that the installer connected the drain line from the boiler directly to the neutralization box (our drains are PVC, not sure we really need the neutralization box, but at the very least we are being good citizens by not dumping acidic condensate into the sewer, and this boiler generates a lot of condensate).
