Quote:
Originally Posted by randen
Daox
I wonder if a spacing of tube 6" placed in a plywood groove with a ceramic or porcelin tile thin-set down would conduct heat well enough without an aluminum spreader. I know that a floor-cover of tongue and groove wood would be useless or god forbid carpet but I would bet that a hard surface such as for-mentioned tile would act more like the Cadilac concrete slab.
Maybe some one could try an experiment with a small section to see how well the heat would propagate through the tile.
Randen
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Randen,
Good thoughts.
"Thin set" can be a variety of materials. Some are mostly concrete based where others have a lot of room temperature hardening plastics. Each would vary with the concrete type being the best conductor of heat.
I believe that a good thick (~ 1/2 inch; 1 cm) trowel of concrete based thin set would be a superb distributor of heat when directly coupled to a ceramic, tile, slate, stone or other type surface.
That said, a routed groove in the plywood would be an easy thing to do so that about 1/3 of the PEX pipe is exposed above the plywood surface (5 mm?). The thick layer of mud (thin set) would cover this and the tile could be applied rather easily on top of that.
It also depends on the heating system capacity and the number of degree days you are in. Here is Oklahoma, we use a thinner slab when we put in radiant flooring as it is easy to get a floor that contains too much heat. Our outside temperatures get cold quickly, but then warm up almost as fast. Home air temperature overheating is an issue here when well intentioned homeowners set their slab radiant to 78 F. It is great on cold nights, but when it warms up outside the next day, the heat remains in a thick slab for days (long thermal time constant). This heats air and clients have been known to open doors and windows to vent extra heat in winter.
Despite recommendations to keep the slab at 72-73 F, some insist on pushing the slab temp higher. And then they complain of overheating . . . This is especially true when the radiant system is a natural gas boiler with a huge BTU capacity.
The use of a small heating system (like geothermal) can be coupled to the slab so that the slab is heated in the daytime and the cumulative amount of stored BTUs delivered at night (thermal "flywheel" effect). This often requires a thicker slab (long thermal time constant). This allows a smaller heating unit to maintain a house temp on a cold night when double the number of peak BTUs might be needed.
The issue of how much slab thickness (how much stored slab heat) and how much heat to store is an evolving art.
It might be appropriate to put one long thermal time constant heated slab radiant system in a lower floor with faster responding (smaller time constant) floor above (bedroom areas).
That way, you may get the best of all situations where different living areas can be controlled more appropriately.
Easy to do with a variety of flooring materials.
Steve