I'm about to start the installation of my new Harman PB 105. It will be a remote install, going in a pole building about 100 feet from my house. I plan to tie it into my existing oil boiler/baseboard system. I've been evaluating several options for the underground piping. My initial preference was to run 1 1/4 inch iron pipe, foamed in the ditch. Compared that to 1 1/2 oxygen barrier pex that I would wrap with insulation and pull through 6 inch PVC. Both are about the same price. The least expensive option (for what I would consider an acceptable solution) is to use Thermapex at approximately $12.50/ft. I think the Thermapex is a nice product and it would actually be considerbly less expensive and less labor. The downside is the size of the pipe --the one inch is actuall a little less than an inch ID. My plumber and I figure the thermapex would carry the BTUs we need but we would suffer a bit in performance. Wondering how others dealt with the tradeoffs and if those who have used smaller pipe diameter in thermapex or other products are satisfied?