When you get to flower running your exhaust when the light is out is a good idea to keep humidity down to keep mold at bay with dense flowers growing. Plus accumulated heat at night in the canopy can make your buds airy. Just some stuff to consider bro, you can always get a fan speed controller and run it at lower speeds when the light is not on, that's what I do. Along with an osc fan and a little 9in high velocity fan like you used to have below your pots, keeps my girls plenty happy at night. A small digital thermo/hygro from home depot or such for $10 that keeps track of your humidity and temp hi/lo can tell you what's going on at night and save you alot of headaches...Your B.O.G.'s leafs are starting to fill in a little and look more like mine, but still look a little more sativa dom than mine. I love the SATIVA'S. Take it easy bro, Peace out.
Good advice thanks myco. I'm running all the equipment you suggested above. The thing is, I
will not remember to turn the exhaust speed controller back up after turning it down at night. That's why I was thinking about running a on/off cycle every hour or two to flush the room for thirty minutes. Then when the lights come on with a separate timer, the room exhaust timer is synced to go on too.
At least this way I'm not touching the variable speed controller. The auto switches have up to 48 independent sets so I can tweak them to keep my humidity in check and still shut the fan off at least 50% of the time during lights off (the sealed light exhaust fan will remain off whenever the light is off).
I think I'm going to try it with my analog switches first. If it works, I won't have to buy anything else and I will sleep better knowing all my cool a/c isn't being sucked into the attic and I'm in control of my O2 exchange / humidity at lights out! Win Win!
Maybe I'm making it too complicated, but it's worth a try to save on electricity. The most important thing is that both switches stay in sync during lights on.