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New Garage Radiant Help

We have a DIY garage project and I was told you may be able to help. It's 20 x 40 going to be well insulated, maybe 12" centers on tubing? What kind of round about btus are we talking and how many feet of tubing would you recommend? I really appreciate any help you may have. God bless



  • Brad White_202
    Brad White_202 Member Posts: 105
    A few questions, Carl

    First of all.... soccermom...?? OK... :)

    Well, actually my first questions are, "where is the garage (city, state) and to what temperature do you intend to heat it?"

    Are the walls insulated and will it be air-sealed?

    Is the intended use to be for, well, car storage (As-If anyone does that anymore...) or a workshop?

    Is the slab to be, ... let me change that, Insulate the slab and edges....

    More later.

    Peace Out.
  • singh
    singh Member Posts: 866

    There are links on this site that will help you calculate the heat loss of the garage. That would give you BTU's. You also would want to know if you want to keep the garage at 55* deg or 70* all season long, make a difference in the heat loss . You need to know if antifreeze glycol would be added or not.
    I would be looking at 4 loops of 1/2" tubing 12" on center @ 200' each.

    Good luck.

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Supply House Rick
    Supply House Rick Member Posts: 1,404
    Insulated walls

    and in slab, for cars and stuff only. Located in Dedham, MA. 1 window, door and insulated double car garage door. Thanks

    #my wife's email, I usually don't use internet

  • Brad White_203
    Brad White_203 Member Posts: 506
    I figured....

    that was your wife's e-mail, Carl! Just teasing.

    I am in Auburndale, right up the road by the way.

    If you know the temperature you wish to keep, that is key. Above freezing or say, 60 degrees? Naturally it is an opportunity to melt snow off the cars and "pre-warm" them. So nice.

    You did say well-insulated in your first post- I was rushing for my bus and missed that.

    Devan (D.S.) has your back as a good ballpark place to start. I would definitely use glycol and separate it with a plate heat exchanger or indirect water heater type exchanger, using your boiler as a source.

    The basic principles are:

    1. The closer the spacing, the more even the heat will be. (Less "striping" or perceptible differences in floor temperature.

    2. The deeper the tubing in the slab, the more even the heating. The heat can and will spread out as much as rise up. If you do not use at least R-10 below and all around, this will be compromised.

    3. The more closely spaced the tubing, the lower the water temperature you will need. The further apart, the warmer the water you need. With hotter water further apart, this exacerbates "evenness issues".

    I agree with Devan that the 12-inch spacing will give good results in most garages and slab installations but the variables of actual heat loss and fine-tuning are not known.

    By "fine tuning", you may want a more dense strip with more heat output at the perimeter and less toward the interior. You may have a fixed storage unit which might need less. You may have a walking path or the car ports which want more...

    My point here is that by using more circuits and with variable spacing, you can make it suit your actual needs.

    You will be pleased, I think. Warmer cars, melted snow and then, dryer floors. I might suggest a small fan with a de-humidistat though, for it can be steamy in there during floor-drying.
  • Supply House Rick
    Supply House Rick Member Posts: 1,404
    Thanks guys!

    This site rocks!!!
  • No round BTU's....

    Only rectangular and square btu's. Round btu's went the way of the dinosaurs, along with round boilers.

    Why do a heat loss calculation? THe smallest boiler you can find is going to be too big.

    Plop a 50K BTUH mod con boiler in there and let 'er rip!

    30 X 40 = 1200 square feet. At 30 btu/sq foot per hour (max output of radiant floor heating system) load would only be 36,000 btuH.

    Smallest mod con boilers available (at present) is 50,000 btuH...


    Happy Halloween ya'll :-)_


  • Supply House Rick
    Supply House Rick Member Posts: 1,404
    This is way more than I expected!

    Thanks again
  • Supply House Rick
    Supply House Rick Member Posts: 1,404
    Now I don't need a contractor! Thanks!!!!!!!!

    4-300' loops
    1- 4 port manifold
    8- compression manifold adapters
    1- circ ups15/58
    1- 3/4 mixing valve
    1bag cable ties

    Who needs contractors! You guys are the best at handing over your business to homeowners. Wondering why you phone isn't ringing?
  • Brad White_203
    Brad White_203 Member Posts: 506
    No good deed goes unpunished.

    I suspect that this last "Carl" posting may be a fake, but if not...

    Then, doing good deeds also serves another purpose sometimes.

    Proctology diagnoses of enlargement and flammability suddenly become simpler for one thing.
  • jp_2
    jp_2 Member Posts: 1,935
    2 different things

    there's talking about it and there's doing it!

    guess you won't get much help here when you system is in but doesn't work?
This discussion has been closed.