[Greenbuilding] Solar Hot Water System

[Dusch, Jim E]

Although I realize a superficial question on this is not necessarily
helpful, I need some opinions on solar hot water systems.  The project
is intended to preheat domestic hot water and radiant floor water prior
to sending it through an LP fired Takagi Mobius (which currently does
all the work).  The project is in Maine, where it gets cold for extended
periods of time.  What preferences/advice do folks have:

Closed-loop or Open-loop?  Drainback?  Integral Collector Storage?
Others?