Yes, I have searched the archives and I am reading them. One person mentioned doing a system as I am proposing (Maura at http://www.homesteadingtoday.com/printthread.php?t=105288) so hopefully she will post here again with more details or PM me. Here's what I have, folks. I am in Southcentral Alaska. I live in a rural area. I am off-grid on a solar system with back-up generator and batteries. The house is about 2,000sf on 2 levels, with all modern amenities. We have oil heat in the house now using two Toyostoves. They work but they don't put heat where we want it so we are always running ceiling fans, etc. and having to leave bedroom doors open. In anticipation of this, we planned for a supplemental or secondary heat system (if it works well, it may end up as our primary heating system). So, we ran hot water capable PEX and separate thermostat wires in several different zones under the subfloor as a staple up system and insulated with reflective bubble sheets to reflect the heat up and then used bat insulation to fill the voids before drywalling. We have a very deep basement-like crawlspace so we terminated all the PEX runs there. We have plenty of room to install a system here and all of our mechanical components are here except the electrical breaker box. it is high and dry and vapor barriered so no issues there. We also ran power from the electrical breaker box to the same area in the crawl to power the system on a dedicated circuit. I believe we have 6 zones. We would be using either a propane or an oil-fired hot water heater, NOT a boiler (unless you guys talk me out of it, lol). We were going to put in a fairly small HWH along the lines of 20 gallons or so but not sure what size is needed for sure. Whatever we use, it can't be electric (I don't think) as we are off-grid with pretty high usage already. So then the non-electric HWH would be vented directly out of the crawlspace above the foundation, of course. We only have to worry about national basic life/safety and plumbing codes for bank financing, there are no local building codes. To date, everything we've done has been inspected and approved. We would be using WATER (probably distilled to keep it from being contaminated or high in mineral content), not glycol, in the system. I already have some parts on hand from a guy that engineered a system (without the how-tos of course) using black iron pipes (which I think is a BAD idea for water pipes long-term) and a big, expensive boiler that I found out right quick was a model with a bad reliability history. We took back the boiler before ever unwrapping it and haven't done any work on the system since. We got a bid for an oil-fired boiler from another company that was WAY TOO HIGH and then I started reading about hot water heaters and how and why they work better, especially for closed-loop systems as we plan to use. What we need to do now is figure out how to build a manifold type system and set it up for a closed-loop system with a hot water heater. I've read a lot on this but seen no real diagrams and shopping lists of parts with a good how-to. I've been to the book stores and the libraries and I can't find the two books that have been recommended in the past on other websites. Don't ask me what they're called now as I have forgotten since it's been a while. What I am looking for are some caveats and info. from people that have done this using a hot water heater for this application or from those that know about this sort of set-up. I would also like a diagram or even some step-by-steps of how this is supposed to look and work and what materials I need to get the system running. Thank you in advance.