School me on Hydronic heating, concrete slabs

Discussion in 'The Garage' started by gsweave, Apr 14, 2013.

  1. gsweave

    gsweave Yinz, blinkers are on, JACKWAD!

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    Building a 44'x28' garage/workshop.


    thinking hydronic heat held at 60 degrees, Pennsylvania winters.

    Some say a 40 gallon hot water tank would be sufficent, with a pump. I don't know?

    4" concrete slab. aside from PEX and a suitible manifold for three zones, what do I need, what costs should I project.
    #1
  2. pvangel

    pvangel Team AARP

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    A 40 gallon tank is more than enough, really it is the recovery rate on the heat and what is most cost effective. If you have Natural Gas than a small even 6-10 gal gas fired heater works fine, electric maybe 15-20? You have to evaluate the energy costs in your area.

    I have it in my garage and installed a mixing valve off my boiler so I could run the lowest possible temperature water out to the garage and a temp gauge on the supply and return so I could monitor it. My water going into the slab is 110 deg and comes back at about 90 so am only raising the water temp by about 20 deg.(maybe a little more)which is very efficient.

    Once you get the slab up to temp it takes little energy to maintain. Whatever it ends up costing you just do it, best money you can spend on the garage!
    #2
  3. Motornoggin

    Motornoggin Two-Bit Throttle Bum

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    40 gallon should be plenty.

    I run an outside slab (stupidly steep driveway) on a pump and boiler with no tank. Filled with antifreeze, I just flip a switch when I need to melt the ice off.
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  4. C Squared

    C Squared Now with TURBO!

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    That will work. I have a 32X32 foot 12 foot walls shop in WI.
    Lots of ceiling insulation ( over 24") SIP walls

    I use a 40 gallon Water heater (high efficiency) I have a blend valve etc. and I run the heater at 2 steps off lowest temp. 100? out and maybe 90 back.

    I heat the shop to 60 deg. That is long sleeve shirt comfort.

    I could take pics of the system if ya needed it.
    #4
  5. DUNDERHEAD

    DUNDERHEAD Been here awhile

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    I have a 24 by 30 foot shop I built in 2005. Radiant in slab heat supplied by a wall mounted propane fired boiler made by Takagi. Amazing little unit measures 14 inches by 30 inches high, supplies hot water on demand. Poured slab over 2 inches styrafoam ( more would be better if budget allows ) over 10 inches crushed stone. R-21 walls and R-30 ceiling. I keep the thermostat at 58 year round here in CT. The most comfortable heat there is !
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  6. darkstarmoto

    darkstarmoto Am I evil? Yes I am

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    ^^ Insulation...that is the key to a good radiant system. Must separate grade from slab and also remember to pull the radiant grid up into suspension in the concrete. Leaving it laying at the bottom against the insulation will not be as affective.
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  7. DUNDERHEAD

    DUNDERHEAD Been here awhile

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    Remember when you order the concrete to tell the ready mix plant. Mine had Fiber-Mesh in the mix. I also recall pouring 5 inches thick. More mass is better !
    #7
  8. 3bangin

    3bangin 2010 Tiger 1050

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  9. tommymerle

    tommymerle advwanabee

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    insulate the side of the slab too. I have infloor heat in my shop and house, love it.
    #9
  10. C Squared

    C Squared Now with TURBO!

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    Yup, I have 3" of insulation under my slab and also outside edges.

    Same in the house and garage.
    #10