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radiant heat

ed m
ed m Member Posts: 65
definitely need insulation


  • Lee Nichols
    Lee Nichols Member Posts: 4
    Under floor joist radiant heat

    I have recently built a 2800 sq. ft. house in upstate NY. I decided to use hot water radiant heat under the floor joist, the boiler is fueled by propane gas. The heating system includes hepex tubing and metal floor joist tracks. A general contractor was hired to do the sub-contracting. I have an unfinished basement below the heating system, should there have been some type of insulation installed below the tubing to keep from losing heat. Everytime I have asked the gc or plumber they say it was not needed because heat rises. I belief they took advantage of me because this is the first house I've ever built and didn't know the difference. My biggest question is it common practice to install insulation or not? Any comments positive or negative would be greatly appreciated.
  • Paul Pollets
    Paul Pollets Member Posts: 3,658

    A "staple-up" application with an unheated crawl below should have R30 insulation installed. Radiant heat does not "rise", it conducts through the subfloor. Without the insulation, the downward losses would greatly increase fuel costs and not heat the space very well.

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  • singh
    singh Member Posts: 866

    exactly what Paul said. R-30 insulation if unconditioned space below , unfaced ok. plus it should touch and be in contact with plates.

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  • Derheatmeister
    Derheatmeister Member Posts: 1,572

    Yes you need Insulation,Otherwise you get HEAT Down LOADING!!! Also if you Install INSULATION Install it Foil faced up. and if you are going to install "CANS"(Reset Lights) you must keep the Tubing clear from this!! HM
  • Derheatmeister
    Derheatmeister Member Posts: 1,572

    Then again if one was to keep the Lower level on it's own Heat emitters, and the temp down stairs was set to say 75 then it may work!! but if you keep the temp Down stairs to say 60 because you are not occupying it then you will have a problem !!! Have seen it especially with Garages below living areas. HM
  • Rich L.
    Rich L. Member Posts: 414
    \"heat rises\"

    This is a common miscomception and a question I've asked every new apprentice I've had the pleasure of working with. To clear that one up - no heat dosen't rise, hot air rises. Heat goes in any direction, including up, and is always trying to travel to cooler places. That's why you want the insulation.
  • Weezbo
    Weezbo Member Posts: 6,232
    even insulation beneath the area,

    can only do that much :)

    The floor coverings, the layout of the plates and tubing ,the outdoor temp, the temp of the water to overcome the lack of insulation effects on rim Joists and box beams....on and on... all certainly have some direct bearing on just how and where the heat is going...

    on and on.... is one grey area .that it might be best to have an insulation contractor explain *~/:)

    sealing penetrations around pipe, wires ,ventilation ducting,.... are within that part of where the Heat might be deciding to go , in its fluid journey :)

    that was interesting..
  • GLENN_14
    GLENN_14 Member Posts: 58

    Foil not needed with plates. first two stages of heat transfer with plates is through conduction so you do not want foil in contact with the plates.
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