Grow Tent Airflow: Where to Put Every Fan
By The Budometry TeamPublished Updated
Airflow does four jobs at once: removes heat, removes humidity, replenishes CO2, and strengthens stems. A good layout does all four without blasting your plants.
Part of our pillar guide: Grow Room Climate: Temperature, Humidity, Airflow and Smell
Exhaust goes at the top
Hot air rises. Mount the filter and fan near the ceiling of the tent and duct out the top port. Exhausting from the bottom leaves a heat pocket sitting directly on your canopy.
Intake goes at the bottom
Passive intake through the lower flaps pulls cooler room air across the pots and up through the plants. Keep the intake opening at least twice the cross-sectional area of your exhaust duct.
Circulation fans
One clip fan below the canopy moving air across the pots and lower leaves, one above the canopy moving air across the tops. Leaves should flutter gently, not whip. Constant windburn shows as clawed, leathery leaves.
Run fans 24/7
Circulation and exhaust should never be on a timer. Lights-off is when humidity peaks and stagnant air becomes dangerous.
Frequently asked questions
- How do I know if airflow is adequate?
- Every leaf in the tent should be moving slightly, and the tent walls should pull inward a little from negative pressure.
The full guide on this topic
Grow Room Climate: Temperature, Humidity, Airflow and Smell
Stage-by-stage temperature and humidity targets, VPD explained simply, how to size an inline fan, and how a carbon filter keeps a flowering tent from being noticed.