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Radiant heat and a bloody nose

Tony Viz
Tony Viz Member Posts: 7
I put in a staple up radiant floor heating system in my own vacation house in New Hampshire. I used 3/8 Onyx, 200 foot loops stapled every two feet. 3/4 sub floor and a 3/8 pre finished enginered floor. I have to run my temps between 140 and 160 to get the floor warm and the house comfortable. The problem is the house gets really dry. We have a good sized humidifier and it is still dry. So dry that you get bloody noses. Where the heck is the moisture going?


  • Stack effect

    The moisture is going out the top of the house.

    Stack effect happens in every building. Cooler/drier air enters at the bottom, picks up BTU's AND moisture as it begins to rise and exits at the top.

    Do you have tongue and groove ceilings in the vacation home?

    I witnessed a situation in a log home once where it literally rained in the house.

    T&G knotty pine ceilings with nothing but paper backed fiber glass insulation behind it. The warm/moist air passed through the T&G joints and condensed on the roof. Rained back through the ceiling and the entire ceiling had to be taken down and re-installed. This time the put a real vapor barrier behind the T&G.

    FYI, the heating system has nothing to do with stack effect although some would argue that warm air systems magnify the effect.

    Any chance you can find someone to perform a "blower door test" on the home? It will identify the "invisible" leaks.

    **Edit** I believe that Onix is supposed to be stapled every 6 inches, not every two feet. If possible, tighten up the staple spacing and you may be able to lower your water temps.

    Mark H
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