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  1. #1
    Join Date
    Jul 2008
    Posts
    33

    Default underfloor (radiant) heating

    Hi.
    I'm planning an addition to the house, and I was thinking about using radiant heating in the new space. Is any of this a DIY project? People tell me that it's expensive. How hard can it be?
    It's just PEX tubing attached to the underside of the subfloor. So long as you don't kink or puncture the tubing.........whats the big deal? Can I just run it off of a nearby baseboard line, or do I need to tie it into the boiler? I've put my own copper baseboard line in my living room. (SLANTFIN 80) I sweated the joints with some solder leftover from my old man that he had used in the 1970s.
    It wasn't so tough. I Just gotta remember to shut the water off before I cut into any pipe. (OOOPS!)

  2. #2
    Join Date
    Feb 2008
    Posts
    550

    Default Re: underfloor (radiant) heating

    Given your preliminary experience in installing baseboard, yes I think you could do a diy addition with radiant---but don't fool yourself, you would have to do some research before attempting it---there are all kinds of tasks like stapling up under floor plastic PEX, calculating the amount of heat btu/hr you need to warm the addition, the manifold at the boiler, the proper pumps, mixing valves & other controls.

    Even expert installers run into problems getting the right mix of high heat baseboard (using 180 degree hot water) with radiant (using 100 degree hot water)---a special 3-way mixing valve has to be used with a conventional boiler that is designed for 180 degree hot water---problems with thermal shock & condensation corrosion are possible.

    It is infinitely easier to do an extension of your current copper-finned baseboard, providing your present boiler has the added capacity to heat the addition as well as the existing house.

    Some sites below are a good starting point---could you post the total sq. footage of your house, the sq. footage of the proposed addition, your general location, & the OUTPUT in btu's/hr (listed on the boiler) of your boiler---a determination would have to be made to see if your current boiler is large enough to cover the addition.

    You can do a HLC for each room with the heat loss calculator below, then add up all the rooms.

    Follow the info in the first site below & try to determine the HEAT LOSS CALCULATION for your house, plus the addition--be sure to consider the amount of insulation in your exterior walls & attic the fitness of the windows (drafty or tight), your general location, & how much oil or gas you use over a heating season.

    You can Google "radiant floor heat" to get tons of internet sites, also see if your local public library has "Modern Hydronic Heating" by John Siegenthaler, which has a lot of info & diagrams & photos of a radiant install & is designed for the diy'r.

    http://www.houseneeds.com/shop/atop/...atingindex.asp
    http://en.allexperts.com/q/Radiant-F...diant-heat.htm
    http://hearth.com/calc/roomcalc.html
    http://www.radiantcompany.com
    http://www.radiantec.com
    http://forum.doityourself.com/boiler...er-system.html
    Last edited by NashuaTech; 07-14-2009 at 12:46 PM.

  3. #3
    Join Date
    Jul 2008
    Posts
    33

    Default Re: underfloor (radiant) heating

    I just wanted to know if I would save that much doing it myself. If it's only a $1000. bucks or so to have someone do it,then I wouldn't bother doing it myself. I might install toe-kick blowers too under the new kitchen cabs so as to save wall space. I'm still in the rough planning stage and will figure it out as I go. Thanks.

  4. #4
    Join Date
    Jul 2009
    Posts
    1

    Default Re: underfloor (radiant) heating

    A recent "This Old House" showed PEX tubing being installed on the underneath side of OSB sub-flooring. Won't the insulative properties of OSB trap most of the heat below the sub-flooring and keep it from ever getting into the house? Thanks.

  5. #5
    Join Date
    Jul 2008
    Posts
    33

    Default Re: underfloor (radiant) heating

    Don't know!!!!!!
    I just wanna know if it's worth doing myself. If saves me a few thousand-I may do it myself. If it's only a matter of a day's work for someone to install it ($1000.) then I'd rather have a plumber do it.

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