Hello- and let me first say thank you all for such a wealth of knowledge and advice.  I am about as new to computers as I am to radiant floors, but I have learned what an invaluable tool and resource the internet can be...thanks to folks like yourselves.

Anyway I am a new member and this will be my first post.

I am just about to start building a barn/shop/house structure of my dreams and will eventually be where I hope to retire.  Basically 44x60 and I was hoping to have the option of heating the whole thing at a later date.  The house will be 36x36 with about 2/3 loft.  It will be built on a monolithic slab; vapor barrier, 6" compacted gravel, 2 inch rigid insulation, and 4 inch floor except for the thickened edges.  R19 walls and 38 ceiling, vaulted about 1/3 and lots of glass exposure and potential heat loss or gain. 

I know this is not the way to do things (kinda winging it) but this is somewhat of a last minute change and my only concern is getting pex in the floor and figuring out the heating details at a later date.  Ass backwards- I know, but Im trying. 

Anyway, for the mono slab Im guessing 10-12" loop spacing and 300 'runs to keep balanced.  5 loops in the 36x36, and 4 in the 26x44 portion.  There is a 7" drop from the house floor to the shop floor and I will insulate between as well as under slab and perimeter.

I need to order manifolds and tubing asap and be ready to pour in 3 weeks.  I think I need pex-b? and manifolds I can pressurize before and during the pour?    

My concrete guy is helping me, but he knows nothing of radiant, so I am in charge of this portion.  I understand we want the 1/2 inch pex about 2" from finished floor?

Any advice is sincerely appreciated-  just dont scold me too bad, huh!

Thanks

If the attachment works, here is an example of what Im building- this is actually a horse barn, so I made changes to doors and such but you get the idea.

Also this will be built in Central Oregon; 0 winters and 100 degree summers norm.

nobody?

I start with a heat load analysis.

One must account for windows and floor coverings, then determine radiation (floor, wall, ceiling and supplemental if needed). From this information a material list can be generated along with a CAD drawing for quick installation and future reference. Of course there is the heat source and controls to be considered.

Ventilation and cooling will also be revealed in a property heat load.

But you have made some good guesses by golly.

The great thing about concrete is being able to bury your mistakes.

Nice Looking building,
you are about on track with your ideas and now is the time to place pipe. You can staple to the foam (fast)or tie of to a wire mat. If you chose wire mat look for flat sheet road mat, 7'6"x20' this is easy to work with and you can raise it to the 2 in level. 12 inch or 9 inch pattern will work fine might consider 6 inch in areas with vaulted ceilings, Pex B is fine pipe, place the pipe and manifolds and pressure test and work out the rest later.
Dan

Posted By BadgerBoilerMN on 11 May 2010 06:55 AM


The great thing about concrete is being able to bury your mistakes.

   

Ditto on the importance of a real heat load analysis. Without it the question & answer is as meaningful as,

"How many horsepower does it take to operate a car?  It'll be going on the freeway sometimes, and may have a 3 speed transmission, and oh yeah, it's blue."

You can take a WAG at it, and it might even work, but performance is far from assured.

I am not asking for help with horsepower or BTU's- I agree a proper analysis is critical, but I dont even know all the window sizes or even placement yet...or doors and other essential things required. I do know that I am pooring a floor for this building shortly and only get one shot at giving myself an option for radiant heat down the road. The tubing is relatively inexpensive and I just need to know a safe spacing to lay my tubing. Is closer necessarily better? At 8" spacing do you experts think I will be safe down the road to finish and design a radiant system around? and size my boiler and other componants down the road? As I said- backwards I know, but Im trying.

Thanks Blueridge Co.- do you sell manifolds by any chance? Any recommendations?

Thanks again

Hi Swampy,
yes we sell the entire system, provide pipe lay outs and oddly enough can offer a heat load if needed. We are located in Washington, just down the road. You are right in placing the pipe now, slabs are easy to lay pipe in before the pour, impossible after. Key to the system is 2 inch rigid foam under, and a thermal break around the perimeter.
If you run pipe on a 9 inch pattern in all standard rooms and a 6 inch pattern in the areas with cathedral ceilings you will have it, you may be a bit over piped but in the scheme of things pipe is the least expensive component to place and will help cover any short comings in heat output.
We are glad to help as needed,
Dan

I concur with Dan and I would recommend keeping all loops to 250' if there isn't a load calc yet. 300' is too long in some cases.... might raise your water temp requirements unnecessarily.

at least in any high load or cathedral areas.

You also have some excellent radiant contractors right in Bend who can also do heat load analysis and provide you with what you need. Have you talked to any of them? I can recommend one or two if you need a referral.

Barry E. LaDuke
LaDuke Radiant Sales
Portland, OR

Thanks to everyone for all your advice. It seems my pour has been delayed a bit so I have time to research and plan without being in such a rush.


Also can anyone tell me if I keep all my loops the same (like 250-300 ft) do I still need balancing valves at my manifolds?

Thanks again

Having recently DIY designed and installed PEX in my concrete slab, here are a few things you might want to do.

You can easily make a temporary manifold, just using tubing and fittings, so you can pressure test, and keep the tubing pressurized during your pour. Just cap the return ends and connect the supply ends with Ts with one end connected to a snifter valve assembly to add air, a shut off valve and your pressure gauge. I used conduit elbows to protect the concrete penetrations, and was able to line them up fairly well so they come out of the concrete protected and neatly. I tied the els to a piece of rebar above the concrete level to keep them all in place during the pour, and one side is near perfect but someone knocked the other side whilst they were working the concrete and since we poured in the dark I did not see it until it was too late, though they are still OK.

I used plastic cable ties to tie the PEX to the wire mat and rebar. Don't tighten the cable ties all the way to leave room for expansion of the tubing. Clip all the cable ties so the ends don't stick out of your concrete. I also read somewhere not to put a cable tie in the ends of the loops, but one on each side of the curve, this to avoid kinks in the PEX. I did this though not everyone does. I was worried about all the pointy bits in the rebar and wire mat, so taped them all - but that was probably insane and not necessary.

Everything I have read says to definitely use valves to balance the system, that the physical adjustment of the flow is the best possible way to balance the system, and every system needs balancing no matter how close the loops are in size.

PEX deteriorates in sunlight, so try not to install the PEX too long before the pour, or have tarps handy to cover the PEX if there is going to be a delay in pouring. I have also kept a tarp over my temporary manifold and the tubing coming out of the concrete to protect it from the sun until we get the place fully enclosed.

In the design, make sure you have the hottest water running along the walls with outside exposure and then loop back so the return in on the inside of the house or room - if you are zoning your rooms. I did 4 zones with 3 single loop zones and the fourth zone containing 3 loops. I used graph paper to design the system, did it to scale, and was able to count boxes to get a pretty accurate length of each loop. I then used this as a map when I put the PEX in, and since I was working solo on this, it was very helpful.

When I layed out the PEX, I carefully unrolled the amount I needed using 2 posts 50 foot apart as my gross measuring device. Make sure you leave enough extra at each end of the loop to reach where you plan on putting the manifold. I plugged the starting end, which was the return side, then rolled it out, then cut the supply side end, held on to it so it couldn't get anything in it, and moved the whole loop onto the slab, attaching the supply end to the manifold. I then started tying from the manifold end. It also helps to put the concrete penetration els in place before you attach the tubing to the manifold, if you are going to use them, rather than trying to work them over the plugged return end.

I would be happy to answer any questions though there are folks here with much more knowledge than I have, at least I definitely see this from an amateur DIY perspective.

-Rosalinda

Good info, thanks to all.  I am building my last home, smack in the middle of the 40-acre Ozark valley where I was born.  House is on south slope, with full walkout to south with 10% S glass.  Main floor walkout to north, also 10% glass with 2" lightweight concrete slab and pex.   Upstairs slab was intended to add thermal mass but may not be all that useful since all glass is LowE366, which means that I erred in favor of rejecting heat in summer instead of gaining heat in winter.   Life on slabs for rest of my life is not attractive, but I figured I could always cover traffic areas later, it's just time and money and reduced efficiiency for the radiant. 

Anyway, I bought a product called EZ floor to use in the downstairs slab.  Product is 2" of interlocking underslab foam topped with bumps that accept and hold snapped-in pex in lieu of using mesh.  it also serves as vapor barrier.  great concept, but now I'm wondering whether the pex will be too deep in the 4" slab.  any thoughts?   Any opinions on whether I will need to add extra loops or reduce spacing due to added slab depth?  Also, any opinions on gypcrete v/s LW concrete? I chose LW concrete because it can take a finished floor, which saves money.  I'm using zip strips to control cracking but even if it cracks, my house is supposed to be rustic so unless I can see into the basement I'm ok with small cracks. 


thanks again for any info.

Rob

hi again, I found the answer to my question about pex depth in slab in another topic.  (doesn't matter enough to worry about.)  sorry for not checking thoroughly before posting.  I stlll would like thoughts on my other question about lw conc etc. if anyone has info.  thanks to all.

Swampy, if your building is going to have individual rooms, it is far more important to loop rooms separately than it is to get loop lengths even. use balancing valves.

to the other DIY'er... precutting coils before laying them down? weird technique. never do that... unroll as you go so you don't have to worry about any mistakes and accidentally create a splicing requirement. Just track the length as you uncoil to make sure you're still on track. assuming, of course, you aren't working from any kind of plan.

Rob, I did not think I could handle the 1,000 foot coil by myself on the slab, what with the rebar and wire up on blocks etc, and I did manage to avoid the splice situation, but in retrospect it might have been easier. Given even one extra pair of hands the whole job would have been much easier, so maybe that is the best tip - have help.

-Rosalinda

yes. that or a tubing uncoiler works wonders.

Thanks for all the help here guys-  So I am on track with the spacing, get balancing valves at manifolds, and keep loops around 250?  With balancing valves can the loops be all different lengths and terminate whenever most convenient?  Or is it still critical to try and keep them all the same length?

Thanks again

 

 

loop length + or - 10 % realitive same amount of turns for auto balance, no ballance valves required. try not to exceed 330 feet (3 loops in a 1,00 foot role)
If you zone by room lay the pipe by room, actuators needed on manifold.
If it is one huge zone, flow valves can be an option and added later to the manifolds if needed, we sell a stainless manifold that I personaly like that has add on flow valves should you want them later.
Another option to flow valves is a infrared Lazer temperature gun with digital read out, about $75.00 and you can check the delta T on each loop! You can also use it to see where heat loss on the building is and if the dog is still alive.
Regarding elevating the wire mat, usual this is done after the pipe is attached with dobey blocks, that way you can walk right on the mat and pipe as needed, watch the pointy ends, Bag ties will work a lot easier and faster than zip ties.
Dan

If you have balancing valves there is no need to worry about loop lengths. it's pretty rare that I've seen a project that would not benefit from individual loop shut off capabilities and/or flow balancing. Single big open rooms with equal loop lengths, maybe. But even then it can be handy for air purging to have individual control over loops, and most manifold systems charge you about the same amount (usually exactly the same amount) to have flow meter/balancing valves on them as they do to have just plain balancing valves on them.

So there is no real good reason not to use the flow meter/balancing valve variants unless your flow rates are higher than the meters can handle. You need *some* kind of individual shut off capabilities on any manifold. good practice, anyway.

Actually there is a difference in price, for our manifolds anyway, and the manifolds with out flow meters do provide more flow.
Example SS Stainless manifold shut off both sides 5 loop actuator adaptable $215.00, Add on flow gauges available as needed.
SSX Stainless manifold shut off both sides 5 loop actuator adaptable with flow gauges $235.00
The difference is she SS manifold has an add on flow gauge, easy to replace, provides greater flow less resistance than the standard SSX.
point is that though the price may be close the built in flow gauges do restrict more flow than the add on type as option.
Enjoy your day,
Dan