Building a house in Upstate NY. I’ve decided to use PEX and go with a radiant system, that I will install. My cousin went with 7/8″ thin wall PEX 16″ o.c. between his floor joists. The cost was around 70 cents per foot compared to 50 cents for 1/2″ PEX. But with the 1/2″ stuff, I’ve been told that 2 runs are needed per bay, meaning that it’s actually 70 cents compared to one dollar per each foot of bay. Has anyone used this before. His source was: www.radiantcompany.com, out of Vermont, but www.radiantec.com also sells it and again, they’re out of Vermont.
The only problem that he’s had was using the connections that were supplied. They were the barb type with double hose clamps on each end. A couple of them have leaked and since then both companies have introduced a compressing ring style connector.
Has anyone used or even heard of any of these companies? Apparently their PEX is custom make with a thinnner wall allowing greater heat exchange capability. My building inspector has OK’d the pipe’s lower PSI rating.
-Aaron
Replies
Not an expert on PEX for radiant heating yet but I just used NRTRobs services here for designing and supplying my materials and am very impressed with their knoweldge and service.
http://www.nrtradiant.com/
Lots of good DIY info on the site.
Daniel Neumansky
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
I am not an expert on this by any means, but I would assume 2 runs of 1/2" is much more efficient than 1 run of 7/8". Two runs of 1/2" have a surface area of 3.14 vs. 2.75 with 7/8"
Thatr is my thought. The 7/8" gives greater mass and flow rates, but what he is after here is heat exchange surface, which is greater with the 1/2" doubled. If I wanted to plan a system that needed longer runs, I would go to larger. I had one where we placed the manifold and controls about 60 from the boiler and ran 2" pex to and from, then heated that floor from that manifold.
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7/8 is more commonly used in ice-melt applications. The thermal mass needs to be higher.
If you are going to let cheap drive the radiant heating bus, you won't like where you end up. Go with the design formulas from the materials manufacturer. Vanguard, Kitec, Onyx and three good brands, but each has different design requirements. The payback on radiant comes later in energy efficiency and the value of the greater level of comfort, but only if the system is properly designed.
We won't use anything but 3/8" in joist bay applications because it's so much easier to work with. If you're looking for help with designs and materials for a DIY app, I'd cast my vote for NRTRob. He's a class act & will steer you in the right/best direction based upon sound engineering.
7/8" in a joist bay? A single run per bay? Never will I do that.
I used Radiantec tubing for three of five zones in my DIY home - I bought the tubing prior to doing all my homework and have worried about it since - the first problem is the most obvious - 7/8 tubing is really hard to work with - large tubing needs a wider turn radius when bending around corners. The large tubing is difficult even when laying on remesh but particularly through floor joists. And because the tubing is thinner than traditional PEX it seemed more apt to crimp when forced - the experience was a small nightmare.
My lasting concern came after I finished my system - a plumber friend told me Radiantec's propietary tubing isn't really PEX and doesn't/won't provide the oxygen barrier I need when using the standard steel wheeled circulating pumps I had bought for a closed loop system like mine. I figure if/when the pumps fail I'll switch to the more expensive bronze impellered/pumps, but if I knew then what I know now - I'd go with standard 3/4 or 1/2 PEX and standard fittings - and local advice. - Brian
I wouldn't be concerned about the circulator, I used Radiantecs 7/8" pex at my own house 22 years ago and have yet to replace the 007 steel pump on my system.
My only complaint with there stuff is the fittings. The barb fittings and hose clamps seem to work loose and leak if I don't tighten the clamps about once a year.
I have done a couple dozen radiant jobs since then, all with wirsbro and propex fittings, much more reliable and easy IMHO.