1. (Michael Chandler discussing why the Zip System is problematic around doors and windows…) LINK
2. (Various folks discussing …why drainback solar hot water systems (ala Tom Lane) are actually better in all climates than glycol-mixed systems) LINK
The most important thing to note here is that it seems to be the case (from what I have read recently) is that the claim that drainback systems are problematic in freezing weather is incorrect. The reality is that… built correctly, unpressurized drainback systems, even in New England and other freezing climates are LESS problematic — easier to acheive a high solar fraction, less maintenance, and more resistant to components failing causing catastrophic system failures/damage. At least that’s what I gather detailed information published by the below names:
Countless counter-examples include: Tom Lane in FL (homepower.com), Gary Reysa in MT (builditsolar.com), and Alan Rushforth in PA (rushforthsolar.com), and Tom Gocze in ME. (Google will lead you to the truth!)