Braveblaster- I will have a 50 gallon water heater in the house as a buffer/storage tank with gas backup, also providing DHW, the tank has 2 sets of ports so I will hang a 40 plate exchanger and a pump between the spare 2 ports on constant circ with a Ranco controller regulating tank temp. When the tank falls below 130, the Ranco activates a pump to circulate the underground across both plates and reheat the tank to 160 at which point the underground stops flowing. On a call for heat, another pump will draw from the 40 plate in the house (same one used to heat the tank) and send hot water to the air handler. I've got all the parts here, just haven't had time to execute the plan yet.
Heat550- Because Insulseal would cost $6000 and take 100+ hours to complete, versus $600 and 8 hours, And my current ground loss is only 2.5 degrees in 350 feet with the Logstor. If I had it to do over again the first time, I'd spray it in the trench. But seeing as 50 feet of my Logstor is under a concrete slab and the boiler is on the far end of that slab, that's not an option now.