I have been told by a few hardwood (bamboo and oak) floor suppliers that
laying these 5/8" thick floors over the hydronic heating tubes is ok. The
oak floor planks are in one piece whereas the 5/8" bamboo flooring has three
layers with the middle one perpendicular to the other two.
Just a few days ago I had a contact with another supplier who said that only
bamboo veneer over a softwood is suitable for laying over hydronic heating.
I'm in the process of laying a 1/2" engineered plank (three layer, oak)
floor over a concrete pad with radiant tubes installed. According to the
manufacturer, it is fine as long as the floor remains under 85 degrees F.
With concrete you have to use a vapor barrier, and I'm installing it as a
Hope this helps,
Best surface temperature for wood is 80-85F. This is done by controlling the
temperature and flow rate of the water in the tubes under the wood floor.
All hydronic piping under wood floors should be on their own zones (ie. not
sharing water with radiators) as the temperature requirements for under-wood
heating and radiators is VASTLY different.
Are you just installing the heating system now? If so, make sure you have a
'slab sensor' embedded in the gypsum/concrete layer under the area where the
wood is to be installed so it can measre the temperature of the slab and
send a signal back to the control valve/mixer to keep the water temperature
at the correct value. The area under the wood MUST be separated from other
areas where you may be using stone or ceramic flooring.
Suggest that you go to the manufacturer of your heating tubing's web site
for some background information on the electronic controls they offer to
manage each heating zone.
Most wood flooring manufacturers recommend 4" or narrower strips when
radiant heated, but I have seen great installations with 12" wide reclaimed
Temperature control is the key. Don't expect to use under-wood hydronic as
your primary heat source if you have an old drafty house in Minnesota as the
water temperature will have to be too high. On the other hand, if that same
house uses cast-iron radiators as the primary source and you just want to
take the chill off the floors then you are ok.
If your house is built using ICF or SIP panels, then you can heat it
exclusively with under-wood radiant - depending on the exact details of your
home design, location, number of and quality of windows, etc.... YMMV.
Strict attention to detail is what makes or breaks a hydronic under-wood
installation. You need a really experienced hydronic contractor who has been
around and done many wood installations for this
Thanks Larry and John for the very useful info.
The lower floor will be over a crawl space and there will be about 9" of
fiberglass insulation (R19) and a reflector sheet below the heating tubes.
The upper floor will have no floor insulation, so there will be some heat
flow from the lower floor. The house is in the early stages of construction
and will be tight, draftwise and it's near the west coast. There will be
occasional light frost in the winter and very few windows face north, and
when they do, they are very small. . Windows will be wood with double
glazing. The wood strips will be about 4" wide. The hydronics were designed
by a New England company - Radiantec I believe. The whole system will be
divided into zones with independent automatic controls on each. I am not
planning baseboard radiators for the lower floors but if I need to put
carpet on the upper floors, I'll use baseboard (water) heating and they
would be separate zones with their own controls. This decision is still in
the melting pot.
The walls will be 6" thick SIPs.
Thanks again and enjoy the weekend.
You may want to do a Google search on Radiantec and see if there have been
any consumer complaints. I seem to recollect reading that there may have
been some for some of the DIY companies but I cannot recall which one(s).
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