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[coolidge]

Insulation only wet on the surface touching the plastic.

[coolidge]

Thermal images.

[coolidge]

Now that is interesting, just went out to stoke the fire and the low water alarm is on, ran in and added some.    Ohhhhhhhhhhhhh

[E Yoder]

So are you thinking there's a break in the Pex in the slab that's causing the moisture?
The low water cut off will trip after only dropping maybe 10 gallons, it's pretty high in the tank

[coolidge]

Never happened before, anything is possible at his point.

[slimjim]

Has the floor ever frozen, I need to see your manifold, I recall seeing thermal imaging that looked like a loop may have had little to no circulation

[coolidge]

Don't believe it ever froze, usually start heating in Sept. but there is one strange area that showed up this afternoon.

[hondaracer2oo4]

Did you do 5 inches of stone under the slab as a capillary break? There must be ground water moving in and out from between the insulation and slab. If water had just gotten between the insulation and slab it would make it's way up and out.

[coolidge]

All sand

[hondaracer2oo4]

That may becausing your issue. Why did you go with sand under the slab? Here is a really good article. http://www.greenbuildingadvisor.com/blogs/dept/musings/polyethylene-under-concrete-slabs

[coolidge]

Good article Honda, thank you

Local gravel guy said it would be good to use for drainage.
It wouldn't surprise me if the vapor barrier or foam board was compromised from the pour.

I guess pouring over the existing floor is really my only option?
Sh:t like this isn't in my toolbox, so I do appreciate all the help, suggestions.

[slimjim]

Good article Honda.

[mlappin]

Interesting read, I’ve seen several done the wrong way. Most notably a slab at an ag dealer, they wanted a heated outdoor slab for power washing equipment. I don’t recall any gravel being used under it for starters, the vapor barrier went under it, then they were placing sand on the vapor barrier to fill any imperfections before placing the insulation, then to top it all off they filled any irregularities in the foam board with sand.

I’ve also read numerous other articles, vapor barrier on top on the insulation then they just stapled the pex down right thru the vapor barrier.

Still weird that it worked the first year then failed the second. Only thing I wonder is did you have a dry year the first year, then it got wet the second and water found its way under the slab?

[hondaracer2oo4]

I ended up following exactly how that article said to do it. First we put down 4 inches of clean round stone, then 6 inch high beveled at 45 degrees on top around the frost wall with 2 inch xps , then2 inches of xps foam board down on the whole floor, then vapor barrier and then stapled the pex right through the vapor barrier. I went back and forth with that placement of the vapor barrier for a while on some of those green building sites with some guys. Ultimately they said if you add up the holes from the staples your are going to end up with about 1 1/2 square feet of 'missing' vapor barrier which is fine. My concrete guy would have put sand under the whole thing for sure if I didn't say anything. Everything I read said that the stone is very important as a capillary break so as to not carry water up through the soil to the insulation and the slab. I haven't hooked mine up yet but I hope it works! I still need to build my closed system radiant manifold.

[schoppy]

My 50x60x16 shed is a floating slab and I just pulled up my pictures taken during construction. I couldn't remember where my poly vapor barrier was. I put down a bed of pea gravel over my sand base then the vapor barrier then my high density 2" Styrofoam which had the pex stapled to that. As soon as the shed was done, I put up rain gutters and downspouts with buried tubing to route the water away from the shed. No issues since construction.

Do you have rain gutters and downspouts with drainage pipe to carry away water Coolidge?