So I have plans on putting pex down on my existing slab and putting a skim coat of concrete over it. It's a 4320 sq. Ft greenhouse. I have a central boiler 6048 paired with 2, 44gph pumps. Couple questions for you all to ponder along with me.... Pex size. 5/8 or 1/2" ? Trying to stay in the 250' to 300' range for loops. Anyone have experience on slab thickness? Is thicker better? 2" or 3" on top of existing? I know this is probably missing a lot of initial needed info but I thought I would get the conversation started and let the questions develop as we go. Thanks guys!
But I have to work with what I have. The 3 heat exchanger Dan set ups are not cutting it below zero and it kills the boiler temp. Looking for something to take the edge off with constant radiant heat with the floor
mmmm,, remembering heat loss calculation what are dimensions of green house.. I got square footage but with 250 foot loops un-insulated slab are you sure this will even be effective?
Dang. I wish my brother still communicated with our family. He engineered radiant systems for years. You definitely need a reflective insulation under the pex. Foil faced bubble type? Source a few pool solar covers. If $ wasn't an issue reflective surface+ foam+air entrained concrete then pex+ more airentrained concrete.
Yeah I wish I could have had the funds when I first built it but it is what it is... now just have to try to get something in place that helps slow the wood consumption
Oxygen barriered pex is going to be required under the slab with a maximum water temperature of 170 degrees. Six inch turns are a bit tough with the pex also. It WILL kink if you try real hard on as tight of radii as you are suggesting. What will your target floor temp be? With 144' building length and 30' width, maintaining a 300' loop length will also be somewhat of a challenge. I'd suggest starting with graph paper and a scale and draw/adjust/draw/adjust until you get a fairly even loop network drawn out. You really don't want a couple 300' loops and some 400' foot loops and a few 600' loops thrown in the mix. You will find adjusting the lengths of the circuits until fairly equal will be beneficial even if you have to pipe the main hws and hwr to a central location dead center of the floor having the respective loops begin and end centrally instead of out on the edge or on one end. Determine the number of loops required and consider ordering respective pre-made manifolds with ball valves for the loop connections. If you shoot for roughly 12" on center pex vs 6 or 8", on 4300 sq ft, isn't that 4,300 linear feet of pex ? At 300' per circuit, that's 14 circuits. I can see a challenge here. six to eight inch on center will add a whole lot more footage. If height (or $$$$) is not a problem, is there a reason you wouldn't want to pour a 3" slab over 2" styrofoam laid on top of the existing slab ? That would ensure less heat loss downward. With that in place, the double-bubble could possibly serve as a thermal break on the perimeter by pouring over it as it extended from the styrofoam up the wall to a point just above the newly poured slab. It may not provide much, but at least you wouldn't have a slab to foundation direct connection. Or possibly consider a floating slab by extending the 2" styrofoam up the foundation wall and the slab poured up against it....which may or may not be the most desireable but it would give you a great thermal barrier. I'm not wanting to confuse the issue but only want to provide a little food for thought. I'm bad about that..... Disclaimer: This is not design criteria...just random thoughts tossed into the kettle.
I will take some pics with explanations and try to post them. I think it will give a better idea of what I am looking to do. Very good thoughts though. I will have them up in an hour or two. Thanks!
