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Installing in-floor hot water heat for new garage/shop.


Installing in-floor hot water heat for new garage/shop.

Old 01-25-2010, 08:02 AM
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Default Installing in-floor hot water heat for new garage/shop.

I am almost ready to pull the trigger on having a boat/RV garage built. It would be 36x48, and have a concrete floor. I would like to know what's involved in installing the (plastic) pipe, for a hot water circulating heat system.

Does anyone here know how it's done; what dia pipe; spacing; is it layed before the welded steel re-enforcing wire is put down, or on top of it? How many zones?

The idea would be to have a building where the boat/RV would be stored without being winterized. So just keeping the floor warm, without trying to heat the entire building, should be enough.

Appreciate any help.
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Old 01-25-2010, 08:27 AM
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The last one I did was 1/2" pex type pipe that was layed directly to the reinforcement wire 12" apart and zipped tyed every 12" to the wire. As the concrete is poured your finisher pulls the wire to the middle of the slab. The zones are up to you and how you want to maintain different temps in different areas.
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Old 01-25-2010, 08:38 AM
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There are some very good resources on the internet. Google is your friend.
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Old 01-25-2010, 08:44 AM
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go to your local supply and tell them What you need they have programs that will design the system to meet your specs.
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Old 01-25-2010, 09:55 AM
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In another life time I worked in a shop that had one, it did an amazing job.. I researched it a little in 06 to put in the new living room I was doing. Wasn't a good idea to use under hardwood flooring. A lot of info out there for you to dig through, a great idea IMHO.... A area big enough for a boat and RV is pretty big, but you don't need that much heat... Let us know what you decide on, curious... I think I could have gotten away with a hotwater heater, and circulator to keep my 24 x 36 garage from freezing.
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Old 01-25-2010, 10:39 AM
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I have a detached garage in the Tidewater Va. area and it pretty much stays over 32 without any heat. I'd look into the cost of running the system as well as instulation.
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Old 01-25-2010, 10:47 AM
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That's an interesting idea, Mike. I have been googling, and there is a ton of info, but it takes a lot of time to sort thru it all. I did call one place, and they will do a design for purpose, and provide a quote of the materials package. If you buy, then they release the drawings, which is fair.

But now you got me thinking about that water heater/circulator idea. No oil tank; no burner and boiler. I am only wanting to keep a pole-barn, with exterior sheathing and vinyl siding, and interior walls and ceiling insulated, to a temp to keep boat and motorhome from needing to be winterized. That way, I can use either one, when we want to during the winter, and put it back in storage when done.

I should have done this a long time ago, as I don't know how many more years I have to do this. Anyways... that's off topic. Thanks for the idea
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Old 01-25-2010, 11:22 AM
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It's done often in Maine. Look up a guy named Rob at Northeast Radiant Floor Technology. He was on the web a bunch on www.finehomebuilding.com. He'll keep you straight.

In a nut shell I can tell you,
1/2" is most likely OK
Max run of pipe is 350' I recall
My guess is you can get away with 24" center to center runs but a heat calc must be done.
You will have to insulate under the slab with rigid insulation. The thicker the better
Yes, zip tie to the wire,
At your control joints you MUST sleeve the pex
RFH is designed to be turned on and left on.
Nothing is warmer to work off of. You may fall asleep on your creeper
You can run it off a simple hot water tank.
It won't be very cheep. Pipe, pumps, mixing valves, fittings, ect add up to $$$. A Modine or similar style heater is much cheaper to install but the heat will gather at the ceiling instead of being cooler there as with RFH.
Any water spilled on the floor dries quickly.

I didn't do it in my own garage where I have RFH in my house if that tells you anything.

Last edited by Mist-Rest; 01-25-2010 at 01:07 PM.
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Old 01-25-2010, 03:41 PM
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My uncle heats his semi truck tire shop in NW PA with radiant floor heat only, its 100' x 120'. He has the ceiling (40') insulated with 12" bat and the walls 12" bat also, and I believe he said his costs to heat the building in the winter were about $350 (might be a little more now that was about 4 years ago) a month thats with the doors being opened and closed all day. Once the concrete gets warm it doesnt take much to stay warm. I believe he has a 12" slab but it may be 14". I know he had it poured a little thicker than needed. He uses a regular gas fired boiler with 3/4" lines and I think 10 or 12 runs with either 2 or 4 controllable zones.
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Old 01-25-2010, 04:31 PM
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Could you use glycol mixture in the water heater to prevent any freezeup in extreme cold?
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Old 01-25-2010, 08:00 PM
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I believe some do. Especially if its only a temporarily used system.
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Old 01-26-2010, 01:17 AM
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We did a RHF in a boat storage/maintenance building in MA a few years back and the client is very happy with it. 9,500 s.f. maybe 30' high at the highest-basically a big open box that stors big boats in the winter. The guys maintaining the boats love it, no drafts to stir up dust when varnishing brightwork. Constant even heat of 60 degrees. Not cheap but def worth it if you're going to be in the space a lot to work on stuff.
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