Well its a rainy weekend here. I was planning on prepping the trench a bit more and finishing up the last bits of digging, but that probably won't be doable until this coming week once things dry out a little bit.
In the mean time, I've received my pex tubing and the pump for the system along with most of the fittings I thought I might need.
With the bad weather keeping me out of the trench, I figured I would work on getting the insulation ready for it. I am insulating the pex tubing with 3 inches of extruded polystyrene insulation, good for a total R value of 15. This is far more insulation than I've seen from any commercial underground tubing solution I've seen, and its also far cheaper. Of course, its also a lot more work!
I'm starting this with 8 4'x8' sheets of xps that are 1.5" thick. I wanted to buy 3" thick pieces but they were not stocked and I had a vehicle to transport them for only one day. This means I'm going to have to glue a bunch of pieces together to get the required thickness. Below shows the cross section of what I'll be assembling. The tubing will be run in the two voids in the center.
To assemble the foam I'll be scoring/cutting it with a knife and straight edge / square, and then breaking it. Then, it will be glued together with PL300 construction adhesive specifically meant for foam. I was told regular construction adhesive will eat the foam.
Pictures to come soon.