Gary, you mentioned that you are building a solar collector using some surplus extruded aluminum radiant panels.  How's that project coming along?  Will you just paint it black and/or cover it with glass?  I've been considering the same approach (unglazed) mainly for aesthetic reasons, and would love to hear your thoughts.

Yes Kevin, I'll be posting photos soon and asking for advise after reading a book: I'm using copper (hard drawn) and ThermoFinn-U . Dangerous reading for the evil genius:-) http://www.amazon.com/Solar-Energy-Projects-Evil-Genius/dp/0071477721

Here's what I've got so far. I'll be building a box for it and looking for some foam insulation that can hold up to the high temps I may be getting. I've heard that XPS foam-board is not a good material for this. I'm looking for a source for 2" polyurethane. I've got a double pane sliding glass door that I'll use for the glazing and I've built the collector around the size of the glass (3' x 7'). I'm thinking that it will be difficult to split the double pane glass and debating on leaving it intact. Just noodleing around. Any input would be helpful.

Interesting project. When it's time for my new pad, I'm thinking of doing the same. However, since I will be building, I'm thinking of making a large collector as an integral part of the roof. Instead of individual collectors, just making one large one. The collector area would end up flush with the shingles, so there would be no unsightly boxes on the roof.

Some companies manufacture serpentine copper coils, and several of these placed next to each other, running vertically, connected at the top and bottom with the supply and return lines. One large collector. The coils will no doubt be pricey, but I'm thinking that as a whole it would be less expensive than buying many individual collectors. 

I look forward to reading more about your 'experiment'.   

HD has the foil faced polyisocyanurate that is needed.  High temp capable fiberglass should be used between the absorber and the foam.  Years ago a collector actually caught fire when this wasn't done.  The fiberglass cannot have any binders which would outgas and cloud the glazing.

Now I see that you're making a homemade conventional thermal collector.  Because of the aluminum radiant floor plates, I was hoping to see a custom roof-integrated project, like what panelcrafters mentions above.

Dawn Solar makes a system that is sort of like installing Warmboard, PEX, and then conventional metal roofing on top.  They also combine it with PV for a true hybrid collector that looks better than what we're used to.