Would you do this Pex radiant any different?

Steve_175

Wanted you opinion on this guys shop layout/ heating solution. I hope to build my own shop some day (Boston area) and like this method.

http://benchmark.20m.com/workshop/NewShopBuild/05_Heating/Shop_Heating.html

And how do you get the link to just click and play? Attachment wont accept it.

Unknown

You mean

like this? Took me over a year to figure-out how to do that.
Just look up "how to create a link", and you`ll get it.

Dave

mtfallsmikey

Glad I ran into this!

I'm no judge on radiant, but am into woodworking...good site, added it to my favorites...thanks!

archibald tuttle

couple thoughts

You can take these thoughts from a radiant empericist although perhaps some of the radiant scientists will chime in. The general thought processes going into that installation are sound, however:

I interleave the equal loops rather than address a single section of floor as Phil has diagramed. Then if you ever do hole a loop you still have fairly dense coverage if you cut that loop off. I have never diagrammed a system, I just let the 6" mesh guide the install and run right down the grid on a parallel grid wire rather than in between two as PHil has done. I find it easier to keep track of what I'm doing that way. When I lay the mesh I overlap them on register and throw a few zip ties mesh to mesh to keep them there. I get all the pipe runs going at once, so I run out one six inch leg down the building and leave the coil there, go back and get the next and run that, that way I tend not to make mistakes counting grid squares and not leaving enough room to turn the corner and keep all the runs on a grid.

So in the case of Phil's workshop as diagrammed, I would either run all 6 feeds down the cold side around the end down the other side and then looped back the long direction in the building, just like six slot car tracks. I tend to go the long direction so you get less turns. Because of the reverses the tube that has the largest radius turn at one end has the smallest at the other end. Of course you should plan your start and end to bring the ends out of the floor where you want your manifolds. This might mean tightening the spacing on the last run back if the grid count works out wrong compared to the number of pipes you running, although for some reason mine just always seem to fall into place. I find it much easier to do it on the fly, but depending on your temperament and experience there is no harm in a plan.

In theory you can readily turn 90 degrees in one six inch spacing using approx. 6" radius which is well over the minimum for the pipe, but in practice depending on ambient temperature during install, etc. the pipe can have a mind of its own. You use extra ties cinched tight to hold the corners. On the very interior pipe that would have to turn in a 3" radius in order to come back only 6" away (see spacing paragraph below) I tend to let the end expand 3" to each side, i.e. halfway to the next pipe, so its slightly bulbous just at the end of the run. On our crew this is the piece of fruit maneuver, draw your own conclusions as to the origins of this terminology (hint: think Cheech and Chong's "Up in Smoke").

I use 6" spacing not 12". Pipe is relatively cheap (home depot has it the cheapest of late although I am constantly checking sources and they don't always have the 300'ft. coils sitting there that you need although if you plan ahead or have 'em check other stores you can usually get over that hump) and you can't put more in once you pour the floor. These days I'm using barrier tubing which has come way down in price to the neighborhood of 40 cents a foot, on 6" centers thats 80 cents a square foot.

I still tend to use indirect heating methods for the water as much of this is retrofit comfort or add-on space but has not entirely replaced conventional heating requiring hotter temperatures. If you use an indirect water heater, I have experienced no problems with non-barrier tubing in service for 20 years and the non-barrier is about a quarter a foot. I defer to the theorists as to whether or not this is a sensible way to approach it, but it has worked for me just fine. 1/2" is the most common and generally I don't find it more expensive however you could consider 3/8" with this kind of pipe density. That might slightly lower your desirable length or runs, i.e., increase number of separate tubes per area. Again, I just go with my gut limiting 1/2" runs generally to around 250 ft. although I think I've used 300 successfully and that is readily available coil size these days (the 250 came when i used to buy 1000 ft. rolls and cut them into 4 pieces). So using my experience, I'd probably keep 3/8" legs to 200 or 250 max for first trials. I'll let the techies chime in if there is some theoretical limit I'm ignoring in all this.

Again 1/2" has just always worked and been cheap so I never messed with pushing the limits of 3/8" although I happen to have come into a number of 100' coils of non-barrier 3/8" recently for a song when a supply company was moving its warehouse and changing pex suppliers so it was just selling off old inventory. I'm going to do an underfloor comfort supplement install making 26' joist bay a separate loop, so I'll get two bays out of each coil. This is the 8" spacing I would usually employ in non-slab applications. The runs are only going to be 50' that way so I'm sure that the 3/8" will be ample. I already have an indirect running polybutyl based flooring elsewhere in the house. I'm going to try aluminum foil as a heat transfer medium on one side of the floor and get together maybe with the local (to 'the Wall') graphite film guy to try a side by side comparison of install technique and result. More on all that later.

Obviously, if you want to use high tech direct mixing or injection from a condensing boiler which isn't a bad ground up design if all you are running is radiant then stick with the barrier tubing.

One thing I have noticed regarding shops is that if you work in the shop for a week and then go out on a job for a week or have shorter term but epidsodic use, you may want to plan to run the floor fairly cool and plan for supplemental comfort heat during use or while the floor is warming if you anticipate a longer period of use. For a lot of woodshops, a wood stove is the obvious answer, but you could also plan for unit heater or baseboard or something if you're looking for an automatic solution occasionally -- or at least bear in mind the possibility of such auxiliaries in control design and choice of heating source.