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Old 05-20-2011, 12:05 PM   #1
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Hydronic heating over existing concrete


I am looking for some ideas on how to install hydronic heating over an existing concrete basement floor. I am also considering ceramic tile instead of carpet as flooring. The best idea I have had so far is to lay 1" x 3" stringers with the Pex running inbetween them 12" on center. Also installing the metal plates with the pex groove to allow for better heat dissapation. I have a concern though over what kind of flooring I could lay on top of the stringers and still get good heat pass through.

Let me lay it out -

1. Put down a heat reflective barrier on concrete
2. install stringers leaving Pex runs 12" on center
3. install pex and heat dissapating plates
4. Lay Plywood or HardiBacker?? Size unsure ? If you lay 1x3's with tubing 12" on center there would be a 6" gap between stringers.
5. Lay Tile!

After I get the flooring completed I have two options to hook it into my water heating system. I use an outdoor wood boiler which heats the water to 185 degrees and its a closed system. I also use a heat exhanger I plumbed into my hot water heater which works really well. I was thinking the most inexpensive way to add this 440 sq ft room would be to put in a thermostat and zone controlled pump off my hot water heater. If I did this I didn't think I would need the additional pressure tank, etc.
Any information anyone could add would be helpful! I am a Do it Yourself type of guy with no background in construction beside my own home projects.

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Old 05-20-2011, 12:37 PM   #2
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Hydronic heating over existing concrete


You're going to isolate the floor heating water from the water the house uses for bathing and drinking, aren't you?
Ron

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Old 05-20-2011, 09:13 PM   #3
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Hydronic heating over existing concrete


It would be isolated from drinking but not bathing if I used the hot water heater...(not that you couldnt drink hot water) I saw a website with it set up that way and I have to admit I had a little concern myself. My original plan was to just put in an isolated system with another heat exchanger and run it that way.
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Old 05-20-2011, 09:47 PM   #4
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Hydronic heating over existing concrete


Quote:
Originally Posted by Toddh169 View Post
It would be isolated from drinking but not bathing if I used the hot water heater...(not that you couldnt drink hot water) I saw a website with it set up that way and I have to admit I had a little concern myself. My original plan was to just put in an isolated system with another heat exchanger and run it that way.
I would isolate the systems. I wouldn't think you could do this and not violate plumbing code.
Ron
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Old 05-24-2011, 05:26 PM   #5
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Hydronic heating over existing concrete


Cold Climate Housing Research Center just published yet another paper on radiant heat barriers; don't waste your money. If you are not going to insulate under the PEX, you'll be throwing a ton of money down the drain. Any way to put down some rigid foam, then PEX? Maybe foam between your firring strips, PEX on top? Too, they make pre-grooved plywood for retrofitting PEX, too; may be of use to you? I'd be inclined to somehow insulate below the PEX. Any long-napped carpet over PEX will kill the heat flow, in case that was a consideration.
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Old 05-24-2011, 11:31 PM   #6
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Hydronic heating over existing concrete


My first thought about radiant heat over concrete in a basement is that you will be heating the ground. And it gets really expensive to heat the cold, damp earth.

A reflective insulation or radiant barrier can direct the radiant form of heat. But heat also moves through convection and conduction. You're biggest challenge is controlling conductive heat. And I agree that a layer of 2" thick XPS (extruded polystyrene) is more important than a radiant barrier.

Because conductive heat works like a frying pan on an electric stove. The heat from the PEX tubing will transfer down to a cold surface like the concrete instead of your room. There's almost no limit to the amount of heat that can be sucked into the ground.

Adding 2" of XPS will prevent the heat from flowing into the concrete. XPS has a melting point of 212F. So you should be find laying the PEX onto the rigid foam board and then moving on with our plans.

Don't forget to insulate the basement walls with XPS and you'll have an awesome man cave.
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Old 05-25-2011, 06:41 AM   #7
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Hydronic heating over existing concrete


use polymer modified cements & electric grids to result in thinnest install,,, cements can be stamped to provide final floor finish,,, its not all that difficult or expensive.
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Old 05-25-2011, 10:38 AM   #8
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Hydronic heating over existing concrete


Thanks to everyone for the great information. I can't really raise the floor 2 inches but I am getting the point on properly insulating under the pex. I have seen a few products that looked easy to use with built in insulation but they are not cheap. Although I will admit that heating the ground doesn't work at all so I may not have a choice. What is the most inexpensive way to do this? I have free heat (outdoor wood Boiler) but this room doesnt heat well with the furnace and is always cold. I have at least 1500 feet I could cover in this finished basement but I was starting with 440 sq. With your comments I would assume that the product Menards offers for this would also be a bad idea.
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Old 05-27-2011, 10:45 AM   #9
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Hydronic heating over existing concrete


Hey Toddh169,

There's nothing wrong with starting out with the cheapest and easiest projects and working your way to the most expensive ones.

Basements are notoriously cold, damp environments because they are surrounded by the cold, damp earth.

Spending a few hundred bucks to insulate the foundation walls and air seal the rim joists is absolutely necessary if you want your man cave to be comfortable. Free heat is great, but no matter how much you add to an uninsulated space...the results are always the same. Cold, drafty rooms.

I'd recommend skipping the insulation on your floor if it will screw up your stairs or if ceiling height is a problem. Instead, install 2" of XPS foam board insulation to the foundation walls and rim joists. Air seal any gaps or penetrations in the foundation wall with Great Stuff or silicone caulk.

Then you can either frame in a standard wall with 2X4s and place it in front of the XPS or tapcon furring strips directly to the foam board. You must cover the foam board with drywall because it's required by code.
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Old 05-28-2011, 12:01 PM   #10
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Hydronic heating over existing concrete


I'd personally skip the 1x3 furring all together & devise a way to fasten the pex through the foam, and into the concrete floor. One of the manu's may already make such fastener for all I know. I would use a 1" thick 25 psi foam insulation in your case, with 2" of small stone concrete over it. I would also suggest drilling a few 2-3" dia. holes in each 4x8 sheet of foam so the new concrete has a few direct bearing points onto the existing slab. A 2" floor only over foam can certainly move a little, and isn't exactly condusive to a ceramic tile IMO.

Is it ideal? No, not exactly, but it rarely is when retro-fitting hydronic heat into an existing structure.

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