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I thought I had nailed down all the details of installing hydronic radiant floor heat in the soon to be poured concrete floor of my new garage. That is until somebody mentioned I should look into ELECTRIC floor heat. It's a little late in the game to be changing my mind about this, but since it is an important and very permenent decision, I thought I'd ask for opinions from those VMFr's who may have used electric floor heat instead of the hydronic type. What are the pro's and con's?
 

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Electric infloor heat is great for bathrooms and small spaces from what I have been told. There are larger systems out there that do bigger spaces. It is great for instantaneous heat in a very thin mortar or concrete bed.

the hydronic systems. I have come informed of a few different types through the years. One has a sleeve through which the actual hydronic tube is passed through (think of it as a pipe within a pipe in the even the slab breaks). Another is just a pipe supported on little chairs and the concrete is poured around it (when the slab cracks the piping fails) an a final types which uses rubber (and I have no comment on the longevity of this type).

A couple of things to consider when using hydronic in floor heating. KEep you slab pours to the minimum and have lots of control joints which surround the perimeter of your zones. I would consider zones to be about 10'x10' so that way in a 20x20 garage you have 4 zones. if one of the pipes fail in the slab you still have 3 zones left and you wont loose the entire system.

My pops old office had a copper pipe hydronic system in a concrete slab. Junk. IT was always busted until it finally completely failed. The new systems offer warranties on the piping and such. That is how I would be basing my decision making, who offers the best warranty I could afford on the system. Once it breaks you are into chipping out the floor and starting over again with a pipe system and floor.

At least that is the way I am thinking if I was doing my own in floor/pour hot water hydronic system.
 

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Skunked_Red_Head's comments about the importance of zones is a good one.

All of the data I've seen shows a hydronic system with a GROUND source (not air) heat pump is the lowest cost way of doing floor heating.

John Harvey
 

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I have a hydronic system in my woodshop. I placed Kitec tubing on 14" centers, and interleaved zones, as mentioned before. Under the slab is 2" of styrofoam and a vapor barrier. I "simply" rolled out the 6x6 wire mesh, tiewrapped the tubing to it, and made sure the mesh made it to mid-level in a 4" slab as the concrete was placed. My heat source is an electric tankless boiler, but I'd suggest a small gas tankless unit from Takagi ($600 or so). Actually, I have a solar unit for the primary heat, but have never installed it.

I've used electric mats (STEP warmfloor) with great luck under stone in bathrooms, but it's pretty expensive to install. Well, so is Hydronic.

Make sure your slab is well supported, and maybe stay away from hydronic if you have expansive soils.

Happy heat!
 

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The newer hydronic systems use a heavy wall high density polyethylene tubing. There is no comparison to older tubing. You will not have problems pouring it into the slab. Like others have stated, you need good slab pours. Don't skimp on rebar and wire mesh. Not just for the heating either. Good support will prevent spalling and load cracks. A vapor barrier will help retain the heat into the slab. Personally I prefer a boiler over an instantanious heater. But, you need to decide if you are going to keep heat on all winter. A boiler is better at keeping constant heat. Where as an instantainious heater is better for quickly warming an area. Oh and yea, lots of zone valves.

You will love working on a warm floor in the winter!!!
 

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Don't confuse the terms "zones" with maximum tubing runs. The rule of thumb is to have radiant tubing runs no longer then 200 feet @ 1/2 diameter tubing. You can have several runs that are fed from a single zone. I have a four season room that is 450 square feet. I used one zone with four runs to heat my floor. They sell manifolds that are made to any specification. I recommend that if you are heating a garage floor you set the system up like you would for a snow melt driveway system. This means that the water from your heat sourse (boiler etc) runs through a heat exchanger. The fluid in the actual slab loop is a glycol/water mixture. This prevents freeze ups of the slab tubing in the event that you lose power. This also allows you to shut off the system without having to fret over tubing damage from freezing. Also, I'd be concerned with the concrete used for the garage floor. In normal slab pours the material used is not everyday concrete. Its a concoction made specifically for radiant slabs. Trouble is you need a concrete pour of wired 5 inch, that has a slump test that equals 3500 psi if you wish to have a floor that will last along time while having 4000 pound cars sitting on it. Finally I personally would only go radiant floor heat in my garage if I was using the space for not much more then parking. If you intend to aggressively work on the vehicles in the space, I'd pour heavy and go with a good old fashion forced air system. But thats me.
 
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