Underfloor hydronic in the Northeast?

[JFCarbonneau]

Hi,

My wife and I are in the process of buying a modular home in New Hampshire and we would like to use radiant floor as our main source of heating. We have heard however that underfloor radiant heating isn’t working too well with our Northeastern winters. Apparently, the system is unlikely to be warm enough to heat the house comfortably unless we install the pex over the floor with "warmboards" for example?

The floor is made of ¾ inches OSB sheating and we would use aluminum transfer plate to attach the pex tubing under the floor. We would also use one layer of ¼ inch cement HardieBacker® Board before tiling the floor. Will this system work with water heated at 120 degrees for example?

All advices and suggestions are welcome! Thanks in advance!

Jean-Francois

 

[Dana]

Hi,

My wife and I are in the process of buying a modular home in New Hampshire and we would like to use radiant floor as our main source of heating. We have heard however that underfloor radiant heating isn’t working too well with our Northeastern winters. Apparently, the system is unlikely to be warm enough to heat the house comfortably unless we install the pex over the floor with "warmboards" for example?

The floor is made of ¾ inches OSB sheating and we would use aluminum transfer plate to attach the pex tubing under the floor. We would also use one layer of ¼ inch cement HardieBacker® Board before tiling the floor. Will this system work with water heated at 120 degrees for example?

All advices and suggestions are welcome! Thanks in advance!

Jean-Francois

"Staple ups" aren't likely to work in most homes at 120F, but they do in some- it depends on the room-by-room heat load, and the layout of your loops, etc. It's a design issue. Calculate the heat load for each room (ACCA Manual-J style), and how many BTUs you'll need per square foot, then work from there how to get those BTUs into the room with the radiant.

If you use extruded heat transfer plates you'll nearly double the heat flux into the room compared to the sheet-metal types.

In my home my lossiest zone is almost a worst-case scenario: Slightly over the legal code limit for % of wall area glazed, 2 layers of 3/4" plywood under birch t & g, with a wool rug covering about 1/4 of the floor area, and only the thin sheet metal plates, no the extrusions. When it's 0F outside for a sustained period it would take 150F water to keep up, but with an open archway into a less-lossy zone and a tolerance for the occasional 62F morning (in that room only) I run it all at 130F, which is about what my NEXT lossiest zone needs to break-even at 0Foutdoors, with 68F interior temp. If your house is reasonably tight & well insulated, and your design-day temps are above -5F you MIGHT be able to run at 120F for a max temp.

There are plenty of homes running 120F staple-ups in new construction in northern VT/NH/ME- I'm pretty sure you can meet your design goals

 

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[JFCarbonneau]

Thank you Dana, this is very helpful.

JF