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staple up under wood???a good idea or not

jonny88 Member Posts: 1,139
hi,so we are getting ready to renovate.my basement ceiling is completly open.i was going to run a radiant zone on the first floor but after finishing dans book on radiant heat dan has kind of scared me a bit about the effects radiant might have on wood floors. half of the would floor is existing but we are updating kitchen and adding 200sqft to it with new wood floor to match old.anyone have problems with floors buckling etc,thanks in advance for your help.wife read the book and is warning me to get it right or else??????????


  • meplumber
    meplumber Member Posts: 678
    A couple of things to consider.

    First.  The wood flooring manufacturers have been unneccesarily vague on the subject, but here is the rule that we use.  Contact temp of the floor should not exceed 80 deg with real wood.  Even with that there are still concerns.  I have been told that as long as the wood is allowed to fully acclimatize(sp?) to the space, then it limits the expansion and contraction of the product.

    Second, I would consider aluminum transfer plates to try and keep the water temps as low as possible.  A regular staple up job would require 160-180 water.  With the transfer plates, you could drop the water temp to maybe 140 design day.

    Third, I prefer to do floor warming with wood.  Setting the floor, via a floor sensor, to stay at 70-75 deg and then use a panel radiator to fill the btu gap to achieve space heating.

    Good Luck.
  • jonny88
    jonny88 Member Posts: 1,139
    wood floor

    so i see it is a legitimate concern.i was intending to use transfer plates,thanks for your reply and help.
  • Greg Maxwell
    Greg Maxwell Member Posts: 212
    staple up

    We have been doing radiant systems, transmission plate type, rather than direct staple up, for many years with much success. If you do it properly, you will have no problem.

    First, are your floors narrow or wide, and what material. What is the total thickness of the flooring, subfloor included. Those factors will tell you weather you should do a transmission plate method or not.

    If the flooring isnt too thick, and you have narrow boards, you shouldnt have any problem. First thing you need to do is a heat loss calc. Can you match the loss of the rooms that you with a joist plate application? I personally try to keep my water temp to a maximum of 140, but less if you can. I use Wright Soft as my heat loss calcultor, and that will give you the water temp that you will need. You will use 2 runs per bay, and you may be able to use 3/8" tubing. And, modulate the water temp if you can.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    Hardwood Flooring Manufacturers recommendations are flawed...

    I think someone there mistook the maximum allowable floor surface temperature (85 degrees F) as the maximum WATER temperature...


    If wood is limited to temperatures of less than 85 degrees F, then it should be illegal to place hardwood flooring in areas where it will see sun shine. I've seen unheated floors, lying in direct sunshine that had surface temperatures in excess of 130 degrees F...

    They key to floor stability is to make certain that the wood is naturally acclimated PRIOR to placing it over a warmed surface that WILL Drive excess moisture out, unevenly, causing warping, and cupping. The mositure content of the wood MUST be equal to the background relative humidity BEFORE it is installed, AND a reasonable R.H. must be maintained throughout the year, or you can expect movement. Heck, the hardwood floor in parts of my home (unheated floor portions) changes seasonally, and it doesn't even have heat underneath it...

    In an existing situation, I would think that the wood is about as acclimated as it is going to get. Make sure the new woods is as stable and dry as it can be before you put it in, and you should be fine. Limit the floor temperatures to 85 degrees F for the humans, not the wood.

    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.
  • Greg Maxwell
    Greg Maxwell Member Posts: 212
    edited July 2011
    Water temp

    I use 85 as a max emmisive temp as well.
  • jonny88
    jonny88 Member Posts: 1,139
    thanks M.E and greg

    M.E , now i can put mine and my wifes mind at rest as dan mentioned you a lot in his book.thanks for the clarification.greg is will look for that software for a heatloss calc.thanks again,as dan says if you have a ? come here.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,128
    Don't forget

    to buy/rent a moisture meter.  Everyone says 'acclimate', but what good is this if your wood sits there for a week in a house with no A/C running?  Remember, the wood could've been sitting in a warehouse for months.  Do the proper insulation/vapor barrier required (depending on construction and what's below), put in the tubing, hook it up, get the flooring in the room, get the radiant on, and some dehumidification (A/C or dehumidifiers).  Then check both the hardwood, and the subfloor.

    I apologize, because I can't find the emails I have regarding this.....still looking.

     They (anyone in the hardwood profession who will actually kinda-sorta-give you an answer) say, the hardwood should be in the 6-8% moisture range, and the subfloor no more then about 4% more then the hardwood, before installation.  I think these lower moisture content numbers are pretty hard to get, but the gist of the email was equal emphasis was placed on minimizing the difference between the subfloor and the hardwood.

    When I get home tonite I'll sort through the lengthy email discussions and post a summary.
  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    we've done, oh, a thousand

    under wood for full heat with NEARLY no problems. there have been a few. We had a substandard wood product that was having problems even in non-radiant applications, for example.

    Fact: wood will move with moisture. If you are not controlling humidity in a home, and your region has humidity swings, your floor will move with them.

    Fact: wood might be too wet when you get it for your area. the average moisture content for your region should be used to guide when to install the wood floor, whether you are doing radiant or not.

    Fact: radiant heat cannot CAUSE a moisture problem. and all wood movement problems are moisture problems except in the most extreme cases.

    We use 30 BTU/sq ft or 85 degree surface temps as the max. however we also do water temperature reset on nearly all of our systems which helps prevent heavy cycling of heat on the floors and allows temps to be more gradually changed.

    If you do your due diligence with the wood floor, properly designed and installed radiant won't hurt it. If you buy cut rate flooring and don't watch the moisture, you could have problems even without radiant.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • meplumber
    meplumber Member Posts: 678
    Just re-read the last email I got from the wood floor guys.

    It says 85 deg contact temp.
  • jonny88
    jonny88 Member Posts: 1,139

    thanks to everyone who took time out to answer my ?.
This discussion has been closed.