Glad to hear you found what you were looking for easily. The supply houses can also offer you products and expertise the big box stores don't even care about. If you run short on supplies, most of the "little guys" can run you a short order right to the job site with very little persuasion or hassle.

Make sure and take lots of pics, uploading them as you execute this project. Many DIY projecteers considering building something similar visit the site. More real-time, in-the-flesh success stories add to the "git 'er done" nature of this site. Also, seeing what you accomplish as the project is in progress can help members spot potential mistakes or help you improve certain aspects before you finish. Especially with a poured slab, once it's in there, it's too late to save something easily. Many members have completed better projects than they started (myself included) using the advice provided by fellow members.

Yup, this is certainly one of those- it started as 'yeah, I want a pad in the barn'
and is currently at 'yeah, NOW I want a pad that I don't use high quality/cost energy to heat'.
A/C, I blame the hacked heatpump thread for this, of course-
I had one contractor scratch his head and say "this sounds like a science experiment"
and then get really confused when I said "Exactly! That's the fun part!"

It just seemed silly not to spend the $500 on tubing... well, and the insulation...
and the extra construction... and time... to get the 'radiator' built.
After that, I can add heat when we get there.

Nibs, I'd be interested to read an epscrete thread.

t

it seems that the thickness in inches of EPS or XPS under a slab should be = to your climate zone, ie Zone 4 = 4"

Never use Polyiso (the yellow stuff) under a slab as many have.

I'm using 6" of type 2 EPS in climate zone 5 (only a few miles from a county that is zone 6)

Things I found for the floor seem to stop at R10, and that at about zone 4.

The insulation I'm using says not to go over 4", or R20 with it.

So there will be pictures when my hands heal, but I got the grade pretty level, the
foam's down, and the remesh is almost done. Of the 6 or so ways to do it, I think I picked
the hardest. Getting rolled remesh to sit flat is not easy. And dang, that stuff likes
to roll back up and take a bit of foam- and flesh, if it can get it- when it gets loose.
The 12' door is the worst- as I bend it down, wire- by- wire, it wants to lift 5' behind the
door. I stopped tonight because I ran out of staples (yes, I'm stapling it to the treated
skirting boards. It's a pole barn. I gave up) but with more staples, I'm going to stretch
it sideways. And then jump on it.

At least it's stopped raining.

t

Update from the dead-
5 loops under 1800 square feet of concrete, all hold pressure, and ironically, it's been too cold
to do the sealing and finish work to seal up the floor and get a wood stove going!
But the barn's structurally done. The concrete finisher scored the surface, so I'm going
to embed temperature sensors into the scores. I didn't put them into the
slab itself, and then regretted it. But I want to seal the surface where he scored
it, so I've got some tiny sensors, some tiny wire, and a lot of flexible concrete
'crack sealer' and I'll see how it goes. One active and one passive sensor
per zone, roughly in the middle of each. Just for fun.

One thing I learned: when dealing with permits and inspectors,
I didn't think about the ramifications of putting part of a heating system
into a building that was permitted as 'unheated'- I had a heating inspector
who looked at it, made a note, then said "I was never here- this is an unheated building"
winked, and drove off. I can imagine one with less of a sense of humor would
have made my life a lot more difficult...

t

In my new house build I am using Tekmar 519 thermostats with slab sensors.
A good method is to put sensor into 1/2" pex (end plugged) down into slab & the top end goes right into thermostat wall box. Sensors can be easily pulled & replaced.

Yeah, I had read about doing it that way, and had meant to,
but in the panic over inspections, it didn't get done...
...This is going to be a total science project anyway, so this
is just one more... variable? HacK?

Thanks,

t

Be prepared for extra time and effort with laying your concrete- you layer of insulation will act as a water/ vapour barrier, it takes longer to tighten up and kick.

A foot (300mm) of EPS is standard under slab here or alternatively 150mm-200mm of polyurethane foam under screeds. This is in a temperate climate.
Just to put things into perspective.

Holy Cats! Yeah, our climate's analogous to yours- same south sea warming, precipitation, etc. 5c winters, 25c summers.
A foot of EPS is an R- value of something over 40.
Whereas our codes seem to stop at R10 for underslab, nationwide. And it gets a LOT colder in the midwest...

Interesting. Thanks!

t