Outdoor Wood Furnace Info
All-Purpose OWF Discussions => Advanced Plumbing => Topic started by: hondaracer2oo4 on March 10, 2016, 04:59:37 AM
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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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Yeah I have not seen the mechanical tool for pinning down the pex to the foam but I have seen the fish hook style clips that pin down the pex. Anyone think that I should really use 02 barrier pex instead of regular Aqua pex? I think I will be using antifreeze in the pipe and be isolating it from the system with a flat plate.
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I would think regular pex would be fine.
Stay away from pex al pex as it’s all made in China now and the quality is somewhat dubious
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I stapled mine to the foam in the basement. Pretty fast and easy. Only 3-3-1/2" pour though. Works very good. Might have to raise the pipe a little if you are pouring 5-6".
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lust lurking and learning ..... would it be optimal to have the tubes in the middle to the cement thickness ? ..
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every thing I have read on this subject says your tubes should be within 2 inches of the finished floor
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every thing I have read on this subject says your tubes should be within 2 inches of the finished floor
I’ve read just the opposite a few times, the lower in the pour the more evenly the heat spreads out.
If your using a product like Crete Heat the tube is at the bottom of the pour.
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Two items, first all cement contractors I talked to said to staple it to the foam. 2" high density for the weight of the cement and anything your going to be driving on it ( I store my 40,000 lb rv in my shed). Pex always at the bottom of the pour no matter the thickness, heat rises and then makes the entire cement mass a heat sink. Second using O2 barrier pipe on pressurized systems is the standard for all HVAC systems regardless the heat source and the price difference is minimal. This only makes sense since you will be using air vents to get out the air in the system and you don't want additional air entering the system.
I purchased a pex stapler tool from Menards for about $100 and it was the best investment I made. One person lays the tubing in place and the next walks along stapling it down, it is designed to be used walking along. If you lived closer I would let you use mine for free.
I did a lot of research on all my in floor systems beforehand and this is what I was told by all the most reputable contractors I know.
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every thing I have read on this subject says your tubes should be within 2 inches of the finished floor
I’ve read just the opposite a few times, the lower in the pour the more evenly the heat spreads out.
If your using a product like Crete Heat the tube is at the bottom of the pour.
Well, those guys that invent this stuff know a lot more than me so I guess I should have read more, I stand corrected.
But if it was my floor I would ensure the whole slab was insulated including the vertical edges and I would still try and have my tubing nearer the finished floor than the bottom of the slab...I guess I'm still old school.
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every thing I have read on this subject says your tubes should be within 2 inches of the finished floor
I’ve read just the opposite a few times, the lower in the pour the more evenly the heat spreads out.
If your using a product like Crete Heat the tube is at the bottom of the pour.
Well, those guys that invent this stuff know a lot more than me so I guess I should have read more, I stand corrected.
But if it was my floor I would ensure the whole slab was insulated including the vertical edges and I would still try and have my tubing nearer the finished floor than the bottom of the slab...I guess I'm still old school.
Thats how I did my sidewalk, tube in the middle of the slab, on really cold days it leaves streaks unless you turn the heat up a touch, if I was to redo it I’d leave the tube at the bottom of the pour. But I did this 15 years ago when all I had at the farm was dial up yet and doing any intensive research on the internet was a long, slow tedious undertaking.
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When I did my basement floor a few yrs ago I asked around and everyone I talked to said to lay the Pex in the bottom of the concrete to get an even heat. Around my neck of the woods infloor heat is very popular. Just on my drive into work which is 30 mins I see about 20 places that have OWB going.
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So on the topic of floor heat, anybody find a free cad program just for laying the loops out?
All kinds of options on the net I’ve seen, most start around $750, but do much more than just the layout.
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Google cad loop. Free 30 day trial.
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Google cad loop. Free 30 day trial.
Ahh, my bad, also has to be Mac compatible.
I refuse to load Boot camp or any other Windows emulators as then I’d technically have Windows on my Mac and very shortly it would be a piece of crap like every PC I owned before.
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I had 2 friends helping me lay out my loops when I did my shed. As I mentioned it has 10 loops ranging from 225 to 275 feet long. Be sure to label the supply end and return ends of each loop at your manifold and leave plenty of tubing for hook up. The outer edges of the building is where the greatest heat loss occurs and should be the areas where supply from the loops along that area start out first. I used 1/2" o2 barrier pex on 12" centers, my shed is 50'x60' and is also insulated around the perimeters like willieG had suggested. Heats great and very even.
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Thanks everyone. Shoppy, did you have garage doors? Any thermal break across the door opening? I have read both ways from reputable sites. Some say to staple down, some say to attach to the mesh and bring to the center of the pour, no deeper than 4 inches. I think I will staple if I can find a stapler for rent. If not I will zip tie to the mesh.
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Supplyhouse has a stapler for around $200, when done you can always list it on Craigslist or Ebay.
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oh look ... your back will thank you https://www.youtube.com/watch?v=oNWXrhvoWNM
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oh look ... your back will thank you https://www.youtube.com/watch?v=oNWXrhvoWNM
Same as Supplyhouse, one of the reviews suggested slipping a pipe coupler over the magazine to help the feeding once it gets closer to empty. Supplied weight appears to be a little light.
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Yes Honda, see my first post on page 1, 2-20' overhead doors. Cement contractors and building supply stores probably have rolls of thermal break material usually 1/2" or 5/8" thick. The other material I have used is like rubber cow matts cut into strips wide enough to go below the cement thickness and then topped off with self leveling caulk.
I must have paid more like $200 or so for my Malco stapler but well worth it. I may sell it now as no more projects in store for me.
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Back to this again. Any thoughts on vapor barrier under the foam vs vapor barrier over foam but under pex? The guys at green building advisor suggest the latter.
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Sorry, been busy getting my food plots in and cutting wood. All my contractors said the vapor barrier goes under the foam to prevent ground moisture from rising into the insulation. If you put the vapor barrier between the insulation and the pex you will be putting a lot of holes in the vapor barrier if you staple down the pex to the insulation. That doesn't make any sense to me. Also used high density 2" insulation under the cement for greater load capacity.
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The guys over at green building advisor seem a little nuts. http://www.greenbuildingadvisor.com/community/forum/energy-efficiency-and-durability/94096/poly-vapor-barrier-under-xps-foam-board-slab-#comment-173336
It seems like a lot go with vapor barrier under everything with good success. I just don't want to fill it with rain water before the pour. I could try and get a tarp but it will have to be pretty big, bigger than 28x40.
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The guys over at green building advisor seem a little nuts. http://www.greenbuildingadvisor.com/community/forum/energy-efficiency-and-durability/94096/poly-vapor-barrier-under-xps-foam-board-slab-#comment-173336
It seems like a lot go with vapor barrier under everything with good success. I just don't want to fill it with rain water before the pour. I could try and get a tarp but it will have to be pretty big, bigger than 28x40.
A lot of anal retentiveness going on in that thread you posted.
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Others out there with garage in slab systems, pressurized or non pressurized on the radiant side? I plan to fill the radiant side with antifreeze. I will keep the boiler and the radiant separate with a flat plate hx
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Others out there with garage in slab systems, pressurized or non pressurized on the radiant side? I plan to fill the radiant side with antifreeze. I will keep the boiler and the radiant separate with a flat plate hx
make sure you have an expansion tank for the pressurized side (size of tank depends on many things,,,google amtrol hydronic expansion and you may find help)
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Sounds good. I will make the radiant side pressurized and designed just like any hydronic system in a house. Just minus the boiler in the loop.