Radiant In Floor Hydronic - Exisitng Slab

[surfsweb]

Hi,

I have a question that I need answered. Just wondering if this is even possible?

I'll explain my situation first. Then maybe someone can give me some advice. I am building a 24'w x 32'l garage, slab on grade, stick framed, shingled.

I have already done the following:

- Dug the area for the slab, removed all vegetation, soil is good no clay issues, water table and drainage is good, no flooding.

- Poured 8" - 16" of "A" gravel mix as needed, tamped at 8" lifts, to make level base for the slab.

- Slab is 12" thick x 12" wide around entire perimeter with three rows of 15mm rebar. This tapers to a 6" slab for the entire area of the slab with 4"x6" steel wire mesh throughout the entire area, 4" below surface. 15mm 10" long pieces placed around perimeter in slab for 6"x6" curb. Curb also has one 15mm rebar wired to pieces in slab before it was poured. 6" anchor bolts set in curb around perimeter for walls.

- Sill gasket, 2x6 pressure treated spruce bottom plate, 2x6x12 spruce wall studs, 2x6 double top plate, 2x12 headers for all windows, bay doors, man doors.

- 5/12 pitch 24' rafters w/24" overhangs, 2 gable ends, 1/2" 4x8 plywood, clips, tar papered, ice n water along perimeter, both edges and 2 peaks, drip edge, 30 year architectural shingle, w/2 maximum ventilation 301 vents.

- 7/16 4x8 aspenite on all exterior walls, TYPAR, 6 2'x4' windows, 2 32"x80" insulated steel man doors, 1 10'x12' insulated double steel bay door.

- perforated aluminium soffit, aluminium facia, aluminium flashing around all windows and doors, vinyl siding.

I still need to complete electrical and insulate. As you can see I've progressed along with my build. By the way I don't do this for a living, just trying it myself for the first time. It's quite a slow process this way, but it gives me time to learn the trades too. Also quite satisfying.

I was planning on using baseboard electric heat, but have since discovered the wonders of in floor radiant hydronic heating. Sorry about the long winded story, I just didn't know how much information you would need to answer my question.

Here it is:

What options are there for me to install radiant infloor hydronic heating in my garage at this stage? Knowing what I know now I would have done this before the pour.

- I would be able to dig around the perimeter and install 1" blue rigid foam vertically around perimeter to a depth of 24". I would be able to extend the rigid foam from the base of that vertical foam 24"-48" horizontally. Unfortunately any rigid foam under the slab is not possible at this stage.

- I would be able to pour an additional 2" of concrete throughout the entire area inside the 6"x6" curb at the base of the walls

- I would be able to adjust the bay door to accommodate this, and my man doors already have a 2" lip, after entering them, to the garage floor.

If I installed 4"x6" steel wire mesh on the exisiting garage floor slab, attached my 3/8" PEX tubing to it, would a 2" pour over that be enough. Would that still be able to carry the weight of a vehicle, hoist, etc., without damaging the PEX tubing?

Is there another way to accomplish this, is this just a nightmare, is this just too expensive at this point? I would really appreciate any advice or experience that you may have with a situation like this. The reason I want to go this route, it is more efficient than electric baseboard. Also a friend has got me interested in combining this with a solar hot water pre-heater. Trying to go a little green if possible.

Let me know if you need any pics to explain it better. I took lots throughout the stages of my build.


Thanks

S W

 

[Dkramer]

Radiant over existing slabs is no problem. We use a product that attaches to the slab, then the tubing 3/8 or 1/2 pex snaps into it on 12" centers. I would go at least 9" in your case. Then use a concrete with reinforcing fibers added. My concern would be that there is no insulation under the slab, insulating the perimeter will help a lot, but you have one big heat sink under it. It will still work, probably, just higher operating costs. We pour 2" over 1/2 pex so over 3/8 won't be a problem. Haven't done one over garage before however. Won't be an issue with cars driving on it, as the existing slab is supporting the weight, I'm not sure about a hoist, but I would think the pad under the hoist feet would be big enough to spread the load so as not to be a problem. As you already know it would have been better to have it in the slab.

 

[surfsweb]

We use a product that attaches to the slab, then the tubing 3/8 or 1/2 pex snaps into it on 12" centers. I would go at least 9" in your case. Then use a concrete with reinforcing fibers added.

... We pour 2" over 1/2 pex so over 3/8 won't be a problem. Haven't done one over garage before however. Won't be an issue with cars driving on it, as the existing slab is supporting the weight

Thanks for the reply.

What product is it that you use to attach the PEX to the floor?
Could you send some pics or a link to the pruduct?

Wouldn't attaching a 4"x6" steel grid to the floor, with the PEX attached to it also work?

My main concern was the weight of a car or truck on the PEX with only 2" concrete pour around it, 1 3/8" above it.Would it be better to run the rows of PEX parallel or perpendicular to the length of the vehicle. I really appreciate the information.

Thanks.

 

[jklingel]

First, where are you? If it is cold there, you are going to get KILLED by fuel usage, I bet. No insulation under radiant floor is the worst possible scenario. Heat loss (Q) for a given area is a function of temperature differential and 1/R value (U value). Small R, big Q. Big temp diff, big Q. Radiant floors range from about 72 to 85 degrees. If you need the floor on the warmer end, then Q is larger. That perimeter may need as much as 4" of XPS around it, down a couple of feet into the earth, too. This may be a case for a different heating method and rugs, unless you can throw some XPS down, THEN the new slab. Good luck w/ whatever you do. j

 

[Dkramer]

Thanks for the reply.

What product is it that you use to attach the PEX to the floor?
Could you send some pics or a link to the pruduct?

Wouldn't attaching a 4"x6" steel grid to the floor, with the PEX attached to it also work?

My main concern was the weight of a car or truck on the PEX with only 2" concrete pour around it, 1 3/8" above it.Would it be better to run the rows of PEX parallel or perpendicular to the length of the vehicle. I really appreciate the information.

Thanks.

Sorry it has taken so long to get back on this, I don't visit here as often as I should. Hopefully you can still use the info.
Here is a link to the product I have used before. I am sure there is similar products from other companies. http://us.heatlinkgroup.com/en/product/heatlink-heating/89000/pipe-tracking-38-12-and-58
We used construction adhesive to attach them to the floor, which was concrete.
I really don't think vehicle weight would be a problem, but I'm not an engineer. If you are concerned about the lift, then figure out were the lift will go and don't put tubing directly under the supports.

 

[Dkramer]

Here is a picture showing an installation using the above product.