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  1. #1
    Join Date
    Oct 2006
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    Hi, new member here.

    We are building a new house in SC Wisconsin. 32x44 envelope, full main and first floor, 32x24 loft. There will be no basement as our soil is pretty bad (clay, rocks and very wet), basically slab on grade and 2.5 story house. No carpeting, all tile or wood floors. Total heatloss is ~44K BTU/hr.

    We are general contracting together with our friend HVAC guy (he has the both HVAC and GC license, insurance) and subbing only concrete and plumbing (by the code).

    Now, we are pretty much decided on hydronic floor heating. As we are getting mixed advice, there are questions we have:

    1. Visquine over the grade, then 2-4in of sand, 2in foamular, pex piping, mesh w/ties to press it down and then 4in concrete floor. (other options are foamular only 8ft around perimeter, no visquine, staples instead of mesh).

    2. One zone in the main floor, 2 zones in first floor, 1 zone (loft w/ 2 bedrooms) on the second floor.

    3. Gas boiler with big tank electric water heater in front of it also running hot water (option is just a holding tank).

    4. Biggest problem... AC/vent

    Any advice or help is greatly appreciated as we would like to avoid putting conventional H/AC furnace.


    BTW, I forgot to mention that both floors are 16" trusses (2x4 plates and webs), most of exterior walls are 2x6, tall south wall (with big windows) is 2x8, roof trusses allow for R-50.

    [Edited by witom on 10-21-2006 at 02:43 PM]

  2. #2
    Join Date
    Oct 2006
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    So, am I understanding you correctly? You don't want a air handler or any other A/C unit in the house, but you still want conditioned air for the house.

  3. #3
    Join Date
    Oct 2006
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    Thread Starter
    Well, if we go with radiant heat all over the house, we would like to avoid putting another heating system. But what we found out, putting just AC with ducting will be ~same (from ~$1K less to ~3K more) than full conventional heating/cooling.

    What other choices do we have? Hydronic cooling?
    How would we deal with ventilation?
    Any other advice?

  4. #4
    Join Date
    Jul 2000
    Northern Wisconsin
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    As for the radiant heat: With wet ground close under the slab you want to definately put a vapor barrier down... the thicker the better. Definately insulate!!!!
    The difference in heat loss from a slab without ground water within six feet of the surface and one with moisture near the surface is DOUBLE. You are only going to stop this loss of heat to the earth with insulation. R-10 minimum and R-20 is better. Cost more up front, but you'll save in terms of fuel bills to pay the difference in a few years. Not to mention the fact your floor will heat more evenly with a lower water temperature.
    They make a stapler and staples that are designed to staple the tubing directly to the insulation.
    Zoning is your choice and should be decided by use of the room and floor coverings from area to area. If you're using standard Heat Pex tubing you'll be limited to approximately 300' loop lengths anyhow... this tends to make zoning easier to layout.
    With radiant heat I would always opt for a high efficient condensing boiler with modulation. I personally like the NTI units
    As for air conditioning: if you don't want the ductwork think about a ductless minisplit. Being in wisconsin also I know the real need here is more in the line of dehumidification verses cooling. A ductless unit installed up in the loft area should do a good job of cooling the whole home and they are great at taking a lot of moisture out of the air.

  5. #5
    Join Date
    Oct 2006
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    Thread Starter
    Great post, Firecontrol!

    So the plan so far is:
    - 2" 150 R-10 insulation around 3'9" frost wall (no drain tile, no tar, no gravel, no taping, no Z flashing)
    - 4-6" of sand over the grade inside
    - visquine vapor barrier (not taped edges)
    - 2" of 250 R-10 insulation (code says it has to cover the whole floor, no heatsink)
    - 1/2" pex clipped down or pressed down with mesh rebar
    - 2x6 walls with 1" R-5 outside, taped tyvek, 5.5" fibreglass bats or blow, for total of R-27 to R-31 on the whole wall thickness
    - about R-50 on the cathedral ceiling and flat ceiling

    Now, more questions:
    - Where can I get more info about that ductless minisplit AC?
    - Would I need air quality/humidifier (Broan? ductless?)
    - Why 300' loops is all than can be get for PEX. It's sold in 500' (local Menards, ~$0.23 per foot) and 1000' (eBay, ~$0.28 per foot).
    - Are 2 zones OK in the slab or it should be one (whole slab will keep heating up with 1 zone turned on, right?)

    If not ductless minisplit AC, have anyone heard about and their 2in1 box boiler/chiller units?

    Thanks again!

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