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radiant heat in a garage

I have a customer who is building a 30x30 garage to house and work on antique cars. He wants to use hot water in-floor radiant heat with a coal fired boiler. The floor is to be 6" concrete with 2x6 framed walls and a truss roof.Questions: What material is best to use for the piping under the concrete? Can I run high temperature water(i.e.160-180 degrees)? How deep to set the tubing/piping under concrete? Iam considering Pex, Kitec, but homeowner wants copper. Any help is greatly appreciated.


  • Saggs
    Saggs Member Posts: 174

    The 1st thing you should do is checkout a couple web sites. Try www.ipex.com and www.burnhamradiant.com. These manufacturers both have very helpful free radiant instruction manuals. I just built a 28x36 garage with 1/2" wirsbo pex tubing spaced about 10" apart and closer along the perimiter. I put down a thick poly vapor barrier over the compacted grave/sand base. I have frost walls around mine so I put 1" blue board around the inside perimiter of the frost walls about 8" high. This gives some insulation around the sides and gives a little room for crush or expansion of the concrete against the frost walls. On trop of the poly I laid down 2" blue board across the entire area. On this I stapled the pex tubing and brought all my supplies and returns to one area where the utilities come in. I also used the 2" blue board all along the outside of my frost walls from the footing to the top edge. This will help keep the heat in. It's pricey but worth it in the long run. This was my own place and my 1st radiant in concrete job. Make sure you use pvc bend supports where the tubing exiits the crete, these can take some abuse that may occur. Use the Pex not the copper,that would be nuts. I keep my supply temp at about 100degs and the room temp at 54degs, I'm in N. VT and it works awesome!! Nothing like laying on a warm floor when your bustin' your knuckles on your kid's beater. I have 6" walls and 14" in the attic, it keeps an insulated storage area and bathroom on the 2nd floor warm as well. I piped it into my existing Buderus in my home. Try to talk this dude into oil or gas boiler, he'll be happier in the long run. Good luck.
  • Tim Doran
    Tim Doran Member Posts: 208

    I would suggest that you start out with a proper heat loss calculation and work from there. We can assit you if you wish. 800-321-4739

    Tim D.
  • kevin coppinger_4
    kevin coppinger_4 Member Posts: 2,124
    ditto to...

    what Tim said. Get a heat loss done then you can figure boilers...that can be later. Once the concrete is poured its too late to back track...I would use nothing other than PEX for tubing...yes I prefer Wirsbo. kpc

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  • ALH_3
    ALH_3 Member Posts: 151
    Pex etc.

    You might show the homeowner some pex-al-pex. It behaves more like soft copper so he/she might like the "feel" of it better. Coal is an incredibly cheap fuel(also incredibly high maintenance and dirty to have around antique cars or engine parts), but a 6-24 Vitodens boiler could simply be plumbed directly into the system with no mixing or extra pump...no relays, no mixing valves, easy addition of an indirect water heater, no external controls. Just hook up 4 pipes(2 if no water heater), 120v in, the outdoor sensor and you're done. You dont even need a thermostat. It's just a thought.......


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