Mr. Bean,
Thanks for joining the discussion.
We have a thread on Exergy
HERE that I started, where I tried to introduce some of the aspects of Exergy. Sometimes it's a bit of a tough sell. If you'd care to contribute to that thread, consider yourself invited.
Also, the issue of exergy, and how to design a low exergy radiant floor is certainly appropriate to this thread.
Having looked at quite a large number of radiant floor web sites, I have concluded that most of them assume that fossil fuel will be the heat source, and then all the high-exergy rules of thumb flow from that, wide PEX spacing, under-subfloor installation, etc.
I looked at your page on Low-Exergy
Energy • Efficiency • Entropy • Exergy • Efficacy, and it's great, just great.
If you would be so kind, I'd be interested in hearing what you have to say about designing & building a low-exergy radiant floor, as that is my main DIY project this summer.
My current thinking is to use 1/2" PEX on 6" centers, and use extruded plates (flange up) over high-density rigid insulating board (which I have yet to locate), with 1/4" Hardie-backer over that and topping that with linoleum.
Your thoughts?
-AC_Hacker