Hydronic tubing above or below subfloor?
I’m getting ready to do renovate my 1956 cape cod in Delaware. The house is heated with hot-water baseboard radiators throughout (supplied by a 120,000 BTU gas-fired boiler at 180F). In the remodeled kitchen, I’ll be putting cabinets where the existing radiators are. Floor will be ceramic tile rather than the current vinyl sheet, over 3/4″ plywood.
While I could install toe-kick radiators under the cabinets, I’d prefer in-floor hydronic heating throughout the kitchen. I’ve had it in a couple of prior houses, and liked it a lot.
My question: what are the operating cost and performance tradeoffs of an “above-the-subfloor” system like Warmboard, vs running tubing under the subfloor (in aluminum extrusions such as Wirsbro Joist Trak)? How much performance do I lose by the tubing being under the subfloor rather than above? If I can avoid it, I’d prefer not to add the floor thickness of a Warmboard or similar product (I’ll already be adding thickness with cement board and tile).
The kitchen is currently above a non-conditioned, non-vented crawlspace, but as part of this project I plan to insulate the crawlspace walls per the excellent instructions on this website. In general, though, the house is insulated as well (or I should say as poorly) as might be expected of a 1956 house.
Thanks for any assistance and comments – I’ve done a fair amount of searching on this particular question without success, but a link to a previous post would be great as well, if one exists.
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