Love to see what you do. The reason for the 12v, Fermtroller can control it directly versus needing an SSR. If you use PID instead, game could be different.
Yeah - I'll be using an older AMX processor that can only handle about 1A per relay @ 12V. It seems a lot of solenoid valve require more than that - do you know what yours takes?
I have 6 Altronix RB610 relays here, so I'd planned to use the 12V to fire the 110 relay to hit the solenoid.