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  1. #1
    Join Date
    Jan 2008
    Posts
    6

    Radiant Heating Tubing:

    The radiant heating design for my house has Pex tubing in the basement slab, and the staple up tubing under the main floor is Onix. The rationale for using the Onix is, it is a quieter when the system is operating, but most web site that I have visited for radiant heating all show them using Pex tubing for the staple portion as well. My question is besides the Onix being three time the price of Pex, what are the advantages of using the Onix under the main floor of the house?

  2. #2
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    4,567
    Onix can be run at warmer temperatures and still be quiet. running pex at these temperatures can be noisy. to avoid the noise, heat transfer plates can be used so that the water can be run at a lower temperature. adding the plates can raise the cost to higher than onix.

    another option is to use an outdoor reset mixing system or a high effiency boiler with outdoor reset. this will vary the water temperature to reduce on/off cycles of the system which is when the noise occurs.

  3. #3
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,841
    In new construction homes, it's best to plan from the onset to use radiant tubing. Doing so allows the wall frames to be built with a double shoe, which allows the use of track panels on top of the sub-floor. The track panels are more of an investment up front but like most energy considerations, delivers a less expensive operation in the long term. You see wood is actually a poor conductor of heat, which is why it's used as handles on some cooking pans. Low density wood insulated and provides relatively poor heating panel characteristics, as opposed to something like a masonry floor, which has excellent panel characteristics. The end result is that any staple-up job will require a higher temperature water to deliver the same Btu's to the room. Using the track panels the radiant tubing is just below the finished floor, reducing the depth of penetration and putting the heat directly into the finished floor, which is usually hardwood, which is a better heat panel than the softer subfloor wood. Having the walls framed with double shoes allows for the extra 1/2-inch of thickness for the track panels and still allows plenty of wood to screw the bottom of the sheetrock to the shoe. Our companies choices for radiant in order favorite to least favorite, are masonry products (poured concrete or light weight gypcrete), track panels, staple-up w/aluminum panels and joist heating. Not all manufactures recommend or approve of joist heating but we've done several jobs using that method and it's worked out just fine. We use the Taco Radiant Mixing Block with injection pumping to moderate the water temperature. You can use the Taco mixing block with or without outdoor reset but we ALWAYS use reset controls. There's just no point to putting in radiant if you're going to only control the water temperature to the coldest day of the year. Kind of takes a lot of the comfort and efficiency out of the project. Maintaining very slow temperature changes in the water pretty well guarantees there won't by any noises from the tubing. It's the sudden increase from low to high temps that create the quick expansion of the tubing and can lead to some expansion noise.
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