Hey Mongo, radiant staple-up info
Did you see the article in JLC about the air gap distance and use of Al. plates? It seems that less air gap (Celotex tight to tubing) is better than a 2″ gap which was recommended to me and I think is also what you do, right? Heat transfer through the floor was slightly better, and recovery a little more so.
It also said that use of plates is a lot better than not using any. I didn’t use the plates, and I have trouble maintaining a set temp. when it gets really cold. Basement is toasty. This in a drafty old former one-room school that is getting redone one room at a time (no insulation in most walls).
Question: Does anybody have any experience using the plates? I’m wondering now about adding some plates, or maybe I should just step up the pace on my gut-and-redo projects.(replacing windows, all new wiring, insulation and drywall.) I also never installed batts under the celotex, which woudn’t be hard to do. Any thoughts? Good sources for the plates?
TIA
Bear
Replies
Bear,
For staple-ups in new construction, the BTU calcs hardly ever show the need to use plates. Caveat...I'm in CT. In a sunroom with lots of glazing? Sure, they may be needed. In a remodel like your job? that also sounds like a candidate until you get a chance to tighten the building's envelope. Even when they're required, they can usually just be used within 4'-6' of the rim joist.
I frame floors with TJIs so the celotex gets pushed right up to the bottom of the TJI's upper flange. If framing with 2-by, I'll push it right up to the staples that hold the tubing up. The staples I use have a flat plastic head that cradles the staple, the insulation goes right against the flat cap. That's usually a 1.5" gap with TJIs and a 1" gap when pushing the celotex right against the cap of the staple.
If you're cold, ensure that there is sufficient r-value around the rim joist. In a cold floor that's sometimes th culprit, as it allows the heat between the celotex and the subfloor to leak out the rim joist instead of heating the floor. Normal rule of thumb is three times the R-value under the tubing than is above it. More insulation under the celotex probably wouldn't help right now unless you have carpeting. It sounds like the basement, buried in terra firma, is simply tighter than the upstairs. Still, if the winter chill is wearing you down, plates and additional FG under the celotex may improve the comfort level.
What temp water are you circulating? Staple-ups are usually run hotter than slabs, around 130-140 or so. My staple-up runs at 110 with no problems. Loop lengths are within limits? Proper tubing diameter?
Overall, I'd venture it's the leaky envelope and not the lack of plates that's killing you right now.
I'm outta town tomorrow...I'll check in next week. Email David Thomas as well, he'll be able to offer accurate advice.
Good luck and stay warm!
Thanks for the reply, Mongo.
Boiler temp 180°, not sure of temp in loops after mixing valves. 1/2" PEX tubing, loop lengths not excessive. Rim joists well insulated, but as mentioned, little else is. It seems that is where the effort should go.
I didn't think I needed the plates when I was putting in the system, but started to wonder when it wouldn't keep up when really cold out. But I do think when the envelope is tighter, it will all be fine. Didn't do batts under the celotex yet due to ongoing plumbing and branch circuit wiring projects.
Bear
Edited 12/14/2002 6:23:01 PM ET by BEARMON
I saw that too and was inmterested because I was taught to go down a little. I use the plates with wood floors. You have to be carefull about keeping spaces between and not stapling too tight. The need room to expand and contract. You can get crinkling noise from tham and a sqeeking noise from the PEX sliping as it grows in length. The plates help transfer the heat to the subfloor by conduction instead of relying just on radiation.
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