My grow room contains ~1800 CF. The only inlet air is filtered through a MERV 17. My exhaust will move 300 cfm through 8" duct. How necessary is it to provide constant ventilation, or is it?
I don’t think you need constant in/out ventilation, but you definitely need it to happen regularly. If there’s no air exchange with outside, it’ll deplete CO2, which is the primary nutrient. And risk of mould/powdery mildew and other fungal infections goes up with stagnant air.
You can run your ventilation system on a timer to go on/off often. Always on is good choice too, to be safe. Only reason to not have it run constantly would be your outside air isn’t a good temp/humidity, or I guess energy conservation.
If you’re controlling temp and humidity within the room without issues your air circulation would only be for replenishing CO2. When I was CO2 your plants will suffocate