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Author Topic: Radiant in garage slab  (Read 13219 times)

hondaracer2oo4

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Radiant in garage slab
« on: March 10, 2016, 04:59:37 AM »

Ok everyone, planning on pouring my 28x40 foundation for my garage in about a month in a half. I am looking to put radiant in the slab, I will never get a chance to do it a second time and I figure if I never hook it up not much is lost. My question is any suggestions on the thermal break around the edges of the slab to the frost wall? I have gotten people suggesting 1 inch of foam on the interior frost wall which will be level with the floor when it is poured. Also got suggested cutting 2 inch foam at a 45 bevel and placing the against the frost wall and you will never see the foam at all but it breaks the wall from the slab. Any other suggestions esspecially around the garage door openings for thermal breaks. Thanks.
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Cabo

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Re: Radiant in garage slab
« Reply #1 on: March 10, 2016, 04:16:15 PM »

If you are pouring frost walls, you could pour them 5 1/2" lower then your floor, set long anchor bolts and install a PT 6X6.  I have done this several times (for myself and clients) and have had very good luck.  You could also add 1-2" foam against that is you wanted more of a thermal break.  At the garage door vehicle tires shouldn't have much effect on the foam.  Remember to leave your tubing back from the edges some so you aren't up against the thermal break.  You won't regret putting radiant in your garage.
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Gooseman

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Re: Radiant in garage slab
« Reply #2 on: March 10, 2016, 06:08:32 PM »

Just pored my slab in half my shop this past summer. Pad is 36 X 60 6" thick. I put 2" foam around the outside edge. Up here we have a place that sells the cut-outs from steel clad house doors. The pcs that they cut out are for the decorative windows. I think they are 2' X 3' and are closed cell foam with painted steel on both sides. I put 6mil plastic down then the steel/foam panels down then wire mesh to zip tie the Pex to. This is the same way I did my basement 6 yrs ago. Didn't put heat into the garage  floor this yr but definitely will have it ready for next winter. The house basement is so comfortable in the winter, can't believe I had questions on whether I was going to put the in slab heat when I built the house :o. Can't wait to have the garage warm all winter
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MScott

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Re: Radiant in garage slab
« Reply #3 on: March 10, 2016, 08:27:29 PM »

You haven't indicated your location but I assume that if you live in a cold enough climate to use an OWB you should not be using 1" foam for the frost break. I also assume that you will be using 2" foam under your slab.
In my garage I used 2" foam over 6 mill plastic vapour barrier. I stapled the pex to the foam using a layout designed with the free Loop Cad program, then wired steel mesh to the pex both to protect the pex and to suspend the mesh in the concrete.
I used 2" high density foam cut with a 45 bevel as mentioned  for a frost break around the stub wall and had 6" of concrete poured.
I have the OWB heat transferred to the pex through a plate heat exchanger since I use glycol in the floor. I only keep the garage at around 50F but this has worked perfectly during this past winter.
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schoppy

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Re: Radiant in garage slab
« Reply #4 on: March 10, 2016, 11:11:37 PM »

I did a 50' x 60' steel shed 2 years ago. Pretty much like MScott's garage. 6 mil vapor barrier everywhere with 2" high density foam around entire perimeter walls and beams coming up above cement level which I cut off flush later with top of floor. I have 8" walls which sit on top of slab which brings the inner wall 6" into the slab. 2" HD under slab with 1/2" pex loops on 12" centers stapled to foam and wire mesh on top of that which the contractor then lifted slightly as he poured. At all door openings, two 20' overhead doors and one service door, I used a high density 1/2" rubber matt cut into strips wide enough to get below the pad thickness. This will not break away or absorb moisture and crumble over the years. Then after curing I used self leveling caulk over the rubber thermal break as a final seal. All loops should be close to the same length (I have 10 loops in my shed) and the pex closest to the exterior walls should be about 1' from the inner wall surface. Take pictures in case you have to know where your lines are in the floor in the future. Plan your manifold location and put protective sleeves around the pex coming up out of the floor as well as any sleeves needed for floor penetrations after the pour (i.e. electrical, radiant supply or return, etc.). I also have a center floor drain and two 4'x4' double thick areas (for future vehicle hoist) which I had to work around.

Using a 40 plate exchanger to heat it. My in floor system is pressurized and has glycol in it just in case.

Absolutely love it and has worked excellent, I keep my shed at 55 which for me is perfect.     
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hondaracer2oo4

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Re: Radiant in garage slab
« Reply #5 on: March 11, 2016, 06:37:21 AM »

I am in New Hampshire so yes it is cold. So I guess the 45 bevel cut is the way to go for the thermal break to the frost wall. With the drop downs in th frost wall for the man door and garage doors I will lay foam down on the bottom if the drop down and bevel cut pieces on the side of the frost wall. Everyone seems to have a different technique for doing the thermal break under where the garage door lands on the apron. I am not a fan of using foam board up to a point and then using some sort of chaulking to fill the gap the rest of the way to floor level, I am concerned about the longevity of that technique with cars driving over it but maybe I am just being to cautious. I do like te rubber strips to seperate the floor from the drive up apron but does it provide a good thermal break? If anyone has pictures of their foundation in progress I would love to see them. Is the glycol nescasary in the floor loops?
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mlappin

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Re: Radiant in garage slab
« Reply #6 on: March 11, 2016, 06:42:09 AM »

If your always going to heat it and have a backup heat source in case of a unforeseen failure wit the OWB, then I’d say glycol is not necessary but is cheap insurance against a freeze and possibly having to replace the entire slab.

I’ve found several good diagrams on google of various techniques for thermal breaks.

http://www.aimradiantheating.com/store/floorheat.html

http://homeenergypros.lbl.gov/group/bestpracticesresidential/forum/topics/designing-for-high-performance-slab-on-grade-part-i-controlling?xg_source=activity

Not sure about the cost but manufactured products are available for thermal breaks at the garage doors.


http://www.schock-us.com/en_us/solutions/concrete-slabs-190#cmd
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Re: Radiant in garage slab
« Reply #7 on: March 11, 2016, 03:54:25 PM »

I actually did not use a thermal break at the garage doors and quite honestly I don't think they are missed. There is no sign of snow melting outside the doors and the floor inside seems to be uniformly warm. I'm sure there is some loss of heat that might be more evident if I kept the garage at a higher temperature but it is not something I have noticed. YMMV
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hondaracer2oo4

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Re: Radiant in garage slab
« Reply #8 on: March 11, 2016, 04:20:14 PM »

Any pics of the install process? I was going to zip tie the pex to the mesh and planed that they would just lift the mesh as they poured.
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willieG

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Re: Radiant in garage slab
« Reply #9 on: March 11, 2016, 04:57:38 PM »

I used to tie rebar (and install mesh) during my construction years. We used 4 x 4 x 1/4 mesh and never left it to the concrete guys to lift it (it very seldom stays there IF they do lift it!  We always used cement bricks  busted in half and placed every so often to hold the mesh at about middle of the pour or two inches from the surface. The bricks were made out of concrete and were 9 inches x 4 x 2.
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hondaracer2oo4

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Re: Radiant in garage slab
« Reply #10 on: March 11, 2016, 05:07:10 PM »

I assume that pex below the mesh is the way to go if you hold it up two inches, the pex would be getting close to the surface.
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Gooseman

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Re: Radiant in garage slab
« Reply #11 on: March 11, 2016, 05:42:42 PM »

Here is a few pics of my shop. I didn't put any thermo break at the garage door in the shop or on my house garage. Yes the heat goes past the door but I like the way the snow does not pile outside the door and I really don't think the heat loss adds up to a problem for me. I took lots of pics and measurements as to where the Pex is in the shop for future reference. I also left the insulation and Pex out of two 4x4 pads and added extra mesh in that area to install my two post truck lift. I also as stated downloaded the free cad program for the layout and with a couple of mods it worked out great.
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schoppy

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Re: Radiant in garage slab
« Reply #12 on: March 11, 2016, 11:16:07 PM »

I've had 3 in floor radiant systems now between the house and shed and 2 different contractors and they both advised the same setup. Clean sand or pea gravel base leveled out (or sloped for a drain), then 6 mil vapor barrier, then 2" high density foam stapling the pex with special pex staples to hold it in place. They did not recommend attaching any mesh or metal to the pex for possible rubbing during thermal expansion. Not a bad idea to support the mesh as willieG stated.

Typically the in floor system is separate from the OWB system and it does not take much antifreeze at all to protect your investment from damage in the event of power failure or someone accidentally leaves a door open.

Enjoy
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Cabo

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Re: Radiant in garage slab
« Reply #13 on: March 12, 2016, 04:42:46 AM »

I think you would be very happy using the staple method instead of tying onto the mesh.  Very easy to install and I think that most supply houses have the stapler for rent/use. 
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willieG

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Re: Radiant in garage slab
« Reply #14 on: March 12, 2016, 06:13:39 AM »

I think if you look around on the net you will find clips that actually clip to the mesh and the pex and hold the mesh off the ground
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