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Air sealing for Ultra-Fin

JakeNY
JakeNY Member Posts: 3
I just saw my brother’s new house and he had Ultra-Fin installed. He was told it doesn’t matter which way he installs fiberglass batts with kraft facing, and no air sealing was done.
I was planning on helping him insulate the rim joist with XPS, and was wondering whether there is any reason why the holes drilled to route the pex should not be sealed with foam. Caulk or spray foam along the joists where they meet the subfloor? Rigid foam under the UF and then Roxul? Am I on the right track using these conventional air sealing methods?

Comments

  • hot_rod
    hot_rod Member Posts: 18,195
    the rum or any cold walk needs to be insulated for both heat loss and air gaps. foam blocks as you describe installed with those cans of expanding foam

    Just batts should be fine below fin
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,839
    Don't forget to isolate zones in the joist bays. That transition between the kitchen and the dining room, if you don't use XPS to delineate the zone, you will get trans zone migration of heat. Maybe not a big deal, but you have an opportunity to do it right, right now. No sense in putting heat where its not needed. It will cause discomfort due to over temp, eventually. Think like energy, flowing from hot to cold...

    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • JakeNY
    JakeNY Member Posts: 3
    On an 8” joist, if 5-6” is dedicated to the UF system, how do you support the remaining thickness of the batt that doesn’t fit in the joist? Roxul better than the pink stuff, right?
  • Our last Ultra-Fin job had 8" joists. You just need 4" (2" above the UF and 2" below) and then used 4" Roxul (R-15) in the bays and 6" Roxul (R-23) at the joist ends.
    The Roxul is a tight fit and won't go anywhere unless you've got rats in the crawlspace.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
    cnmdesign
  • JakeNY
    JakeNY Member Posts: 3
    Thanks, I’m in southern NY.
    I have been doing a lot of air sealing in my own home this winter and have been using Roxul instead of the pink stuff and it’s great stuff to work with in comparison to fiberglass.
  • HomerJSmith
    HomerJSmith Member Posts: 1,923
    edited March 2018
    I would like to know the thermal efficiency of Ultra-Fin to standard Rehau transfer plates stapled to the bottom of the sub-floor, insulated for back loss. Air is just not a great conductor of heat energy, especially convection. Conduction, I would think works better. Besides, you don't insulate tight against the transfer plates but keep the insulation 2" below the tubing, the best of two worlds--conduction and convection.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,839
    Conductivity is the king of heat transfer,,, Air is actually a terrible conductor of heat, hence why we use hydronics. UF requires water temperatures in the area of 180 degrees F in order to deliver the goods. It has its applications, but not in the world of high efficiency heating. I think a person could do the same thing with copper finned tube element...

    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • hot_rod
    hot_rod Member Posts: 18,195
    I have done a few UF jobs running 150SWT, it all depends on the load you are covering, BTU/ sq. ft .

    Wasn't all that long ago suspend "bare tube" pex systems were showing 16 BTU/ sq. ft with R1 covering and 140SWT, by some of the pex manufacturer Design Manuals :)

    I think it is good product for adding floor warming to a fin tube system on a conventional boiler, for example.

    Their website has all the details you need and independent testing by the Canadian Warnock- Hersey labs.

    I'd like to see a time when all hydronic systems operated below 120 SWT, we have the technology.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • My experience out here in balmy California, Ultra-Fin runs at surprisingly low water temperatures: 110-120° on 30° days in an uninsulated house. I would call that high efficiency heating, no?

    I consistently over-estimate the heating curve when the system goes into operation and the home owners get roasted.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour