Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

pex attachment to existing concrete

Troy_3 Member Posts: 479
is still up in the air. These concrete floors are 12
" thick over six floors high. The thought is to use 2" of concrete topping and stain it. I'm thinking that the exposed concrete will conduct the heat sufficiently to the surface. Granted the slab floors will heat as well. This is going to be a slow system to respond. No setback here. The other option is that preinsulated preformed polystyrene blocks. It comes down to cost again. Too bad dollars are always such a concern. These are not millon dollar condos. They are college dorms. The exposed concrete is a plus from a wear perspective


  • Troy_3
    Troy_3 Member Posts: 479
    Pex attachment to existing concrete

    What is the best(quickest) method to attach pex to existing concrete to prepare for an overpour. I'm designing a warehouse retrofit to loft apartments and pushing radiant. The key seems to be an efficient method of attaching 120,000 feet of pex onto existing concrete. If the anchors or labor drive the job to high it won't happen. Any successes? suggestions? Ideas? Help!
  • Ron Gillen
    Ron Gillen Member Posts: 124
    Wire Mesh

    Probably easiest to tie-wrap to wire mesh. What about insulation?
  • Paul Pollets
    Paul Pollets Member Posts: 3,616
    Thermal Break

    Without a thermal break, fastening directly to an existing concrete slab will raise loop temperatures significantly. We've used the Uponor Pex rails, perhaps 1" or 2" foam insulation board and foam clips would be easier. The foam clips tend to pull out of the foam when walked on by the concrete guys, but some have been able to use this method without too much difficulty.

    I'd be running the heat loss calcs to see the real water temps required. A thermal break is required in many jurisdictions, and makes good sense.

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • ALH_4
    ALH_4 Member Posts: 1,790

    Definitely get some insulation between the existing slab and the new slab...even if it is just a thin layer of extruded foam. You might put down 1-inch of foam and either clip the tube directly to the foam or tie the tube to 6x6-10ga WWR.

    If insulation is not possible, I would use steel panel radiators instead of radiant.
  • ALH_4
    ALH_4 Member Posts: 1,790

    It would give you a lot of mass, but why not just insulate the ground level and shoot down some mesh directly to the concrete on the upper levels? Run it on constant circulation with OD reset and use those Oventrop TRVs on each dorm. That should help deal with the mass. Just an idea.
  • Troy_3
    Troy_3 Member Posts: 479
    insulated panels

    Thanx for the advise guys. I'll run the calcs. Does anyone know the name of the company that make the preformed insulated panels. I saw them at ish in chicago. Can't find the lit. Has anyone used them? They had nubs sticking up to hold the tube. That would insulate and hold tube till the concrete gets poured. I was hoping to use 3/4" tube because it is such a wide open space. I want to minimize my manifolds.
  • ALH_4
    ALH_4 Member Posts: 1,790

  • Ron Gillen
    Ron Gillen Member Posts: 124

    http://www.beaverplastics.com/beavercurrent/insulworks.html This is the site for the foam with the little nubs
  • Dave_4
    Dave_4 Member Posts: 1,405

    I have done this. Use Dow Corning Fan-Fold insulation. (3/8" closed cell foam). R3.4. Place welded wire mesh on top if this anf pin down here and there with powder actuated pins and a small piece if sheet metal as a washer. Zip tie tubing to this wire. Low cost. Easy install.
  • Tim Doran_4
    Tim Doran_4 Member Posts: 138

    I would probably go with pex rails shot into the existing slab and 5/8" pex. Push the loops out to 500" with a 20 degree delta. Insulation may not be needed on the suspended slabs due to the thickness and relatively small temperature difference. I would keep the spacing tight to keep the fluid temps down and outdoor reset is a must. Wish I still had some of the tools that I developed for Uponor so I could model this to give you a better answer. I guess I need to find time to build some new calculation tools for myself.

    Tim D.
  • Ron Huber_2
    Ron Huber_2 Member Posts: 127
    slab overpoor

    We use insultarp with 5x10 flat wire mesh (lays flat as opposed to mesh on a roll) and nylon ties, either 3/8 or 5/16 pex, depending on the thickness of the over poor, usually at least 1.5 inches. You want at least 3/4" of concrete over the top of the tubes. This method has worked well with very few problems, just make sure you have plenty of ventilation durring the curring process if you are pouring in an existing structure.
  • Tony_23
    Tony_23 Member Posts: 1,033

    www.ezfloor.net although they are not insulated, just plastic.
This discussion has been closed.