Radiant Floor Heating, Where to Start?

[maxpower_454]

Hi all, I have a 30' X 40' X 12' pole building and am looking to pour the concrete floor soon so I'm starting to think about how to design my radiant floor heat system I plan on installing. I know next to nothing about these systems so I'm wondering where to start?

I'm thinking I need 4 loops but not sure what size tubing, what to use for an electric 'boiler', pump, etc. Anyone have any good links for me to read? I'm surprised there isn't a sticky on this. I do not have gas in my area so electric or propane are my only options but even propane is getting expensive.

 

[tdkkart]

Keep reading......you'll find most of what you need here.

 

[Highbeam]

You're 4 loop guess was right. Here's the rough basics:

1/2" barrier pex.
300 foot loops, all within 10% of each other.
12" spacing.

Worry about the boiler, pump, and manifold design later. Your focus right now is the stuff in the concrete.

 

[maxpower_454]

You're 4 loop guess was right. Here's the rough basics:

1/2" barrier pex.
300 foot loops, all within 10% of each other.
12" spacing.

Worry about the boiler, pump, and manifold design later. Your focus right now is the stuff in the concrete.

Well I plan on putting my boiler 1/2 way down the long side of the garage so for the 2 loops farthest away from the boiler I get at least 320 ft if the loops are in a 'zig-zag' pattern. Is this the correct way to install it or should it be in kind of a circular pattern in each loop? Hopefully you can understand what I mean.

Also, a guy here at work used 3/4" for his. is 1/2" ok? Would 5/8" be good?

A few more:
1- What do I attach the tubing to? I didn't plan on using rebar but I guess I would need it to keep the pad from cracking and shifting as well as something to attach the tubing to?

2- What kind and thickness of insulation should be underneath the tubing?
3- Should the tubing be in the middle of the pad thickness or can I just attach it to the insulation?
4- What should I use for expansion joints with the tubing? I obviously can't saw cut.

 

[Highbeam]

My shop is a 30x60 with the boiler location at the halfway point. 6 zones. I ran away from the boiler across the building (30') and then turned 90 degrees towards the far corner. Then back and forth doing parallel rows until I had to run back to the boiler along the original path. You can do it with 300 foot runs, just takes some layout experiments. If you can't use CAD, then even a sheet of graphing paper. My layout resulted in 6 "blobs" with each blob beings a separate zone.

1/2" is standard. I have yet to hear of a good reason to use anything but 1/2" pipe but plenty reasons not to. Price, bending radius, depth in the mud, etc.

I used wire mesh with a 6" grid over the whole slab on top of the foam. The pex was attached to the grid with zip ties. The grid made 12" spacing extremely easy to maintain. Wire also adds some strength to the concrete.

Use 2" EPS or XPS under the slab. 15 or 25 psi but the general consensus is that 25 psi is worth the small upcharge.

The tubing can be at the bottom or in the middle. I prefer the bottom to keep it away from sawcutting and anchors. Some folks staple the pex right to the foam and then wire or rebar on top of the pex.

Yes, you sawcut. Sawcuts never run the whole depth. Mine were only 1-1.5" thick and worked perfectly. Pretty slick really, the slab cracked right in the bottom of the cuts just like they said it would.

 

[jack stand]

I paid a radiant design Co. The shop is 38'X64' with 16' walls. Very well insulated and in Maine. All 7 loops are 1/2" and 18" centers. Very satisfied. Water temp design is 112 deg. Tied to 6x6 mesh on top of #4 bar on a 2' grid.

 

[maxpower_454]

2" of foam?!?! Wow, I might be able to get 1" under there and still get 4" of concrete but 2" will be tough.

Also, how did you guys get the concrete in there with all that mesh tubing and rebar installed? Wheelbarrows don't roll over that stuff too well

 

[Highbeam]

2" foam minimum. That's only R-10. If you plan for it from the start then it is not difficult to place.

I used a line pump to place the concrete on the last several jobs. I haven't had to do a pour from the chute for many years and don't miss it a bit.

 

[theoldwizard1]

I know next to nothing about these systems so I'm wondering where to start?

I know the job is well within the capabilities of most DIYer, but the engineer is not.

Call up a few place in your area. Ask them for a quote. Or Ask them if the will just engineer the job.

Personally, I would pay the extra to have the pros do it !

 

[maxpower_454]

2" foam minimum. That's only R-10. If you plan for it from the start then it is not difficult to place.

I used a line pump to place the concrete on the last several jobs. I haven't had to do a pour from the chute for many years and don't miss it a bit.

Hmmm.. It'd be great if I could fit 2" under the slab but the problem is I told my pole building co (verbally at the site) I wanted it built for 6" stone 5" concrete but they built it to their standard 4 & 4. Since it wasn't on the contract there's nothing I can do. They actually built it with more stone, about 6" so i figured i could easily rake out 1" for insulation but im not sure about 2" ill look at it tonight.

A line pump would be great. Did you pay extra for that??

 

[Highbeam]

Hmmm.. It'd be great if I could fit 2" under the slab but the problem is I told my pole building co (verbally at the site) I wanted it built for 6" stone 5" concrete but they built it to their standard 4 & 4. Since it wasn't on the contract there's nothing I can do. They actually built it with more stone, about 6" so i figured i could easily rake out 1" for insulation but im not sure about 2" ill look at it tonight.

A line pump would be great. Did you pay extra for that??

Yes, it was extra but only a couple hundred bucks. Another benefit of the line pump is that the concrete guys just have to back up to the intake hopper which can be located conventiently. You can pump concrete a long ways.

With a pole barn you can always raise the finish floor to get the foam and mud you want. Just add another row of lumber on top of the existing mud girt. Or did they already side it? Still possible but harder. I poured the concrete after building and roofing but not siding my pole barn.

 

[Drinkin-N-Thinkin]

My 36X54 was set at 4", too. Get a bobcat in there, dig it out and do it right--you'll be happy you did. I think your going to want the 2" foam. I agree with "HIGHBEAM" and I went with 25PSI foam over the 15 (2160 lbs per square foot vs. 3600). In a building that big, you may want it. If you have any pit run in there, you may need to dig it deeper anyway to spread some smooth sand to make it flat and evenly distribute the weight.

 

[maxpower_454]

Would i still be able to put in a 2 post lift with all that foam under there or would the concrete crack because of the foam?

Does the concrete co supply the line pump or did u rent it separate? I checked rental places around here and nobody rents them.

Also, I ran into my neighbor last night who built a building the same size as mine and he went with 4 loops 300 ft long with 1/2" pipe do it definitely sounds like that's what I need.

Should I stick with 4" of concrete? I know some guys put in 5-6.

 

[stingry]

Would i still be able to put in a 2 post lift with all that foam under there or would the concrete crack because of the foam?

Does the concrete co supply the line pump or did u rent it separate? I checked rental places around here and nobody rents them.

Also, I ran into my neighbor last night who built a building the same size as mine and he went with 4 loops 300 ft long with 1/2" pipe do it definitely sounds like that's what I need.

Should I stick with 4" of concrete? I know some guys put in 5-6.

Personally I would go with 5", the extra concrete isn't much and the labor is basically the same. The concrete company should provide the concrete pump or contract for its services. A two post lift will be no problem with the foam insulation just be sure not to put tubing where the two posts will be anchored. Some have put thicker concrete where the lift is mounted. You might want to decide on what lift you want and see what their requirements are for mounting on concrete.

Cheers
Steve

 

[maxpower_454]

I'd like to go 5 but between that and the 2" insulation, I won't have much stone left

 

[Highbeam]

Does the concrete co supply the line pump or did u rent it separate? I checked rental places around here and nobody rents them.

The concrete pumpers are independednt businesses in my area. I pay the pumper, I pay the finishers, and I pay the concrete plant for the mud. If you can't find a concrete pumping company in the phone book then the concrete plant or the finisher should be able to recommend a company. I would rather ask the finishers who they like since the pumper will have to work closely with the finishers during the pour.

A big dollar finishing company can do all of this for you but they will mark up each "subcontractors" price.

 

[Highbeam]

I'd like to go 5 but between that and the 2" insulation, I won't have much stone left

That's all part of the digout. If you want it bad enough you will dig out to a depth deep enough to allow the full section of gravel, 2" foam and 5-6" of mud. That's how bad the company screwed you, now you have to waste some rock.

 

[maxpower_454]

That's all part of the digout. If you want it bad enough you will dig out to a depth deep enough to allow the full section of gravel, 2" foam and 5-6" of mud. That's how bad the company screwed you, now you have to waste some rock.

Oh, I guess I misunderstood what u meant by digging out. I'm not doing what u described. I guess I just don't want radiant heat that bad. I think I can work out a compromise somehow though. I'll have to dig down and see how many inches of stone I actually have. If I can't do radiant heat, I'll go with a more conventional method

 

[Dave Maxwell]

My building company set mine at grade with the needed room under and high enough for water to run away from building. I'm actually having to put 6 inches of fill in on top of the 4 my site prep guy put down after scraping away all the loose soil. Had a garden there for years

 

[maxpower_454]

Well I dug down last night and found I have 4.5-5" of stone. What is the minimum amount of stone that would be ok? What's the purpose of the stone anyway ?

 

[Drinkin-N-Thinkin]

I'd say 4.5-5". The stone is there to provide a solid base and provide a buffer area between the ground and the bottom of the slab to reduce the capillary action of moisture traveling up into your concrete. Also, you don't want water getting under your slab then freezing, it can expand and possibly crack your slab. Try to keep the area around your slab dry (proper drainage from the roof runoff). It also helps to allow the slab to "move" alittle. I would still get a bobcat, dig the stone out put it in a pile somewhere then dig out the required amount of dirt and compact. Foam the sides vertically down 16"~24", add back the stone, compact, lay horizontal foam, rebar/wire, pex then pour a 5" slab (4,000PSI). Depending upon how heavy your load is you will be putting on your lift, you can always mount them on piers then do the flat work around that. You might also want a floor drain--kill two birds with one stone.

 

[maxpower_454]

So no one on here has done a radiant floor with 1" of insulation?

 

[hidollartoys]

I am doing a radient floor with 1" insulation. I am in the Kansas City area and we have more "cooling days" than "heating days". Northern clims benefit from 2" but I have my doubts about 2" in this area. I have found everything from no insulation, to vapor barrier only, to just bubble insulation to just 2" around inter-parameter. Most dont even insulate the exposed slab edge. All report good results and satisfactory performance.

Mine has 2" frost footer insulation, 2" parameter slab insulation, 6mil vapor barrier w/ 1" 25psi under entire slab. My building is all steel, 40 x 80 x 12. My slab is 6"

 

[tdkkart]

So no one on here has done a radiant floor with 1" of insulation?

Again, depends on your location.
Where I am, I'd be more temped to double mine to 4" next time rather than cut it to 1". I honestly don't think you can over insulate the slab, within reason. You sure as hell don't want to be giving away heat.

 

[BadgerBoilerMN]

The depth and R-value of insulation under slab is determined by the heat load for the particular area you are building in. As a practical matter we typically use a 25psi rigid XPS foam board in a 2", R10.

2" XPS will stand up to foot traffic and is quite sufficient for our climate. The substrate better be perfect if you intend to staple tube or roll anything over 1" foam board.

Insulating the perimeter is most important and rarely neglected in good design. The center of the building may not be insulated in mild climates, especially of if the inside design temperature is close to the year round deep earth temperature.

If you use less than 2" foam you may want to tie PEX to flat wire and step lightly lads!

Every radiant floor heating design is a little different.

As for over-insulating. It sounds good but most soil has a certain resistance to heat transfer - remembering the sod covered cabins on the western plains - about R-10 per foot. So using more insulation under a slab than is necessary is insulation better used on areas of higher heat transfer potential such as a garage door for instance.

The one thing we know for sure; bubble foil placed below a concrete slab is not insulation.

 

[maxpower_454]

So for the insulation under the slab, is there any benefit to putting the foil faced "Tuff-R" or "R-Max" underneath? That may be the way I should go since the R-value of that is higher per square inch than the regular XPS. 1-1/2" will give me about R-10 and the regular XPS needs 2" to get R-10.

 

[joes169]

So for the insulation under the slab, is there any benefit to putting the foil faced "Tuff-R" or "R-Max" underneath? That may be the way I should go since the R-value of that is higher per square inch than the regular XPS. 1-1/2" will give me about R-10 and the regular XPS needs 2" to get R-10.

I can't comment on the benefit of the foil face, but "Tuff-R" and the like are usually 25 psi foam, but you will want to make sure before purchasing. We've used tapered polyiso (same thing as Tuff-R I believe) for heated floor applications in the past over pre-cast plank flooring to provide pitch to floor drains. It held the staples just fine as well.

 

[BadgerBoilerMN]

There is absolutely NO benefit to foil, bubble foil or any sort of aluminum under a slab. The listed R-value may be higher for Thermax for example, but the foil does not add to the R-value. Foil faced insulation is intended primarily for wall treatments and only has value as a radiant reflector if an air space is provided.

Without the air space, thermal conduction cancels out any reflective attributes the foil may have added. If you need the extra 1/2" space you will have pay extra for it.

 

[unknown_element]

You're 4 loop guess was right. Here's the rough basics:

1/2" barrier pex.
300 foot loops, all within 10% of each other.
12" spacing.

Worry about the boiler, pump, and manifold design later. Your focus right now is the stuff in the concrete.

visqueen under the foam? The 25 psi foam were talking about in this thread can be had at any local big chain store correct? see link:

http://www.menards.com/main/buildin...50-rigid-foam-insulation/p-1384821-c-5779.htm

A few concrete quotes ive received around my area make it sound like installing radiant heat is not for the typical homeowner to tackle. It does not seem that difficult to do. After the stone is down, lay down visqueen, then your foam, pex, wire, zip tie pex to wire, then pour concrete correct?? So confused!

 

[Dave Maxwell]

That is the stuff I used for my perimeter. Using the 250 for the floor

 

[unknown_element]

That is the stuff I used for my perimeter. Using the 250 for the floor

http://www.menards.com/main/buildin...50-rigid-foam-insulation/p-1384786-c-5779.htm


any pics of how you had it setup around the perimeter?

 

[Dave Maxwell]

 

[maxpower_454]

Ok, so I'm finally getting ready to do my concrete!! It turns out that I have more room than I thought for insulation and concrete so I'm probably going to end up with about 4" of stone, 2" of insulation, and 4-5" of concrete. I'm going to use (4) 300ft loops of 1/2" PVC on 12" centers attached to the metal grating with 3500psi concrete.

I'm about to buy my pex tubing. Are there any preferred places to buy the pex? What about the manifolds while I'm at it?

How much should I overlap the metal grating? 1 square?

Should I put plastic vapor barrier underneath the foamboard or will the foamboard act as the vapor barrier as well?

It's cheaper for me to use 2 sheets of 1" thick foamboard than to use 2" thick foamboard. Is there any downfall to this?

A guy I know who is really good with concrete likes to put the stone, the foamboard, and then about 1" more stone, and then the conrete. Is there any advantage/disadvantage of doing this?

 

[maxpower_454]

Ok, so I'm finally getting ready to do my concrete!! It turns out that I have more room than I thought for insulation and concrete so I'm probably going to end up with about 4" of stone, 2" of insulation, and 4-5" of concrete. I'm going to use (4) 300ft loops of 1/2" PVC on 12" centers attached to the metal grating with 3500psi concrete.

I'm about to buy my pex tubing. Are there any preferred places to buy the pex? What about the manifolds while I'm at it?

How much should I overlap the metal grating? 1 square?

Should I put plastic vapor barrier underneath the foamboard or will the foamboard act as the vapor barrier as well?

It's cheaper for me to use 2 sheets of 1" thick foamboard than to use 2" thick foamboard. Is there any downfall to this?

A guy I know who is really good with concrete likes to put the stone, the foamboard, and then about 1" more stone, and then the conrete. Is there any advantage/disadvantage of doing this?

Anyone?

 

[rburke65]

Bought my kit at Blue Ridge Co. They have kits. Buy the made inUSA kit. Yes one square. Two 1" are ok...stagger seams. Rule of thumb from what I have read is about one foot of pex of every square foot of space.Plastic sheets, then board, mesh, then pex. Good luck. I am finally pouring my 1800 sq. ft. Tomorrow! Thank God!

 

[oilslick]

Good luck on your pours, my guy poured mine and added little to no water and come finishing time it got away from him, now I have to look at a ****** floor for the rest of my life! I saved money and used a guy who did my last garage because he is cheap and uses the company I like and I remember he used to say it comes ready to place no need for straight water to weaken the mix. Most pours I have been around have had a lot of water added and were finished nicely but I always thought too much water! Now I have a **** floor that maybe is stronger than a watered down one I think! I am rambling but just learn from me and get a pro forget the price!

 

[maxpower_454]

Blue ridge co looks like a good place to buy supplies. I like their kits and might go for the 1200 sq ft one since it comes with exactly what I need. Thanks!

Is there anything special I need to do to protect the tubing when it comes out of the floor? Should I get the pieces from blue ridge that make a nice 90 deg bend? Should I sleeve them in anything?

 

[matouse3]

I got the 90 deg bends that come with the kit from blueridge, but they didn't seem adequate to me. I used 3/4inch conduit 90 bends from HD. They were much more stable and provided some protection at the floor level. I had visions of sliding a floor jack or table into one of the pipes without the sleeve and snapping it at the floor.

Here is a link to my build, it has some pics of the bends.

http://www.garagejournal.com/forum/showthread.php?t=152392

 

[maxpower_454]

I got the 90 deg bends that come with the kit from blueridge, but they didn't seem adequate to me. I used 3/4inch conduit 90 bends from HD. They were much more stable and provided some protection at the floor level. I had visions of sliding a floor jack or table into one of the pipes without the sleeve and snapping it at the floor.

Here is a link to my build, it has some pics of the bends.

http://www.garagejournal.com/forum/showthread.php?t=152392

Very nice! Who came up with your tubing layout? Also, is it ok to just attach the tubing to the insulation like that? That really seems like the easiest way to go and then just use fibermesh concrete. Or did you lay the steel mesh on top of the tubing?

 

[danski0224]

Hi all, I have a 30' X 40' X 12' pole building and am looking to pour the concrete floor soon so I'm starting to think about how to design my radiant floor heat system I plan on installing. I know next to nothing about these systems so I'm wondering where to start?

I'm thinking I need 4 loops but not sure what size tubing, what to use for an electric 'boiler', pump, etc. Anyone have any good links for me to read? I'm surprised there isn't a sticky on this. I do not have gas in my area so electric or propane are my only options but even propane is getting expensive.

Where's the load calculation?

Electric boilers **** a lot of juice. Got enough power?

How can you know how many loops and what size tubing without knowing how many BTU's have to be delivered?

Then you have to decide if you want a glycol solution, and how much of a mix because that changes the GPM compared to water only... which may change loop diameter and length to keep the pump sized right.

<holds thumb in air>
Yeah, throwing 4 300' loops in the concrete will do it.
</holds thumb in air>

Good luck.