Can I use passive intake for large grow room?

A few specs: 20x20x9 groom room built inside a room. No windows,doors,etc. 4-1000 watt air-cooled lights,carbon filter(size?? any idea?).

Question: We need to cut a hole in the buildings roof to vent some air into the room. Do we need to put a intake fan in this, or will passive intake do with a good exhaust. Also we were going to run the exhaust this way filter>fan>lights>out. Would it matter if we run a seperate exhaust and use the passive intake? Seen many threads on this but just can't come up with a suitable set-up. Intake and exhaust are important part of this so we want to get it right. Any pearls of wisdom from the pros is greatly appreciated. Also the humidity/temps are critical too.

Do you mean cut a hole in the ceiling? You said roof...


I think you might need 2 separate vents for the air-cooled lights. I run 2 through the same tube and the temperature increase is 20 degrees, 4 might be too hot for 1 pipe.

You want to create a negative pressure to prevent smells from escaping so I recommend an active exhaust and a passive intake at least 2x the size of the exhaust.

The vents for the cool tubes should draw fresh air in and exhaust to the exterior so those should not need to be filtered, it should just be the active exhaust that is filtered.

The room should be able to re-circulate the air on average every 2 minutes, base your exhaust fan off of that figure.

Sounds good, I need to do some figures over.....

i do most of the time. pending on how hot my room is depends on if i run my intake fan or just leave it of..

im doing the same with 11x11 room for flower and 11x11 room for veg and what im doing is hookin up 2 720cfm 8in fans speed and temp controller 1 fan for two lights with Y connector at end tieing both rows of lights to one carbon filter when temps rise fans will cool lights as well as exhaust room i figure why run your fan all the time if temps arent high all the time

Michael Dee said:

Sounds good, I need to do some figures over.....

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