PEX under-floor heating. 3/4″ option? Can I go smaller on existing loop?
I’m pulling the copper from my upstairs hydronic baseboard system and replacing with PEX. I’m going to go with the Wirsbo HePex Plus. I only need about 150′ but the smallest it comes in is 300′ So…I thought this might be a nice excuse to put heat in our bathroom. It used to have a radiator long ago but was pulled out when they did the baseboard heat and for whatever reason, they didn’t see a need to put something back in the bathroom. The catch is that the Wirsbo between-joist panels seem to only accomodate the 1/2″ PEX. Questions: 1) Are there commercial between-joist panels that can handle 3/4″ PEX? 2) could I instead go with 1/2″ PEX? Can I connect 1/2″ pex to 3/4″ baseboards? 3) Do I NEED commercial panels? Is there a DIY panel technique? Sheet metal and XPS maybe? Foil faced insulation?
Replies
1. no, no good ones. you can get some really poor quality lightweights built for large pex from some suppliers but I don't recommend it.
2. use 1/2" PEX or PAP. however, connecting it to a baseboard is not a smooth integration. baseboard is very high temp compared to most radiant. in that case I would not recommend using plates at all and I would suspend the tubing from the subfloor in a 2" air cavity to utilize the baseboard high temps. that said, I'd also have to do a load calculation first to make sure the floor can even heat the room, and if you zone it with the baseboard you are likely to not have very comfortable results. this really wants its own zone.
3. there are no good DIY aluminum panels that I have ever seen. foil faced insulation is not a substitute.
Thanks, NRTRob.
I should clarify a few things as I might have confused things a bit.
The baseboard heat is on our second floor. I'm pulling out the copper between the boiler and the baseboards and running 3/4" pex instead. So it'll be PEX to copper baseboard on that circuit. The reason for this is that the current copper in the crawlspaces froze and split in about a dozen places. The PEX will be easier to run, less likely to split, and will be better insulated by me this time than the copper was by the previous owners.
However, since I'm left with 150' of extra 3/4 pex, I was trying to figure out a way to utilize it in our unheated bathroom.
Your 'suspend' option...would that be to leave a 2" airspace using perhaps XPS underneath (to create the airspace)? Would the PEX, itself, be enough to heat the floor?
Even if it just gives us a warm floor, that'd be an improvement. ;o)
It's a small bath...maybe 60 square feet of floor. It's the original tile (house built in '29), so I'm not entirely sure what's between the subfloor (6" planks) and the tile.
it will do floor warming but typically you'd want two runs of pipe per bay. that's a bear with 3/4".
whether floor warming will do what you want it to or not is another question. practically you're limited to 15-20 BTUs/sq ft that way at very high temps. that may or may not be enough.
it certainly is better than nothing though.
I agree w/ the other poster about combining radiant floor and baseboard heat. I'd approach cautiously. Aren't you only going to use about 60 ft of your excess? Other option is to sell your excess. Should be easy.