FAN Size Calculations:
First determine the cubic size of a growroom, calculate the length x width x height of the
area. For example, if you have a 1m x 1m x 2m tent – the cubic volume is 2m3. Once we have
established the volume of the room we add 25% to factor in the reduction from ducting, friction
and filters (Palmer, 2015).
For our ‘example tent’ the required air exhaust would be 2.5m3 per minute (2 + 25% of 2). To
allow for a complete air exchange every 60 seconds we multiply our 2.5m3 x 60 = 165 CMH
(Cubic meters per hour). Check on the packaging of your fan to see the maximum CMH rating for
that model.
The recommended corresponding intake fan would be 1⁄4 - 1⁄2 the size of this exhaust fan. It’s
better to purchase a fan with a larger CMH capacity and run the fan at a lower setting for better
longevity and quieter audible fan noise.
At this stage, we’d also recommend installing an SMSCOM Fan Controller. This will cleverly
regulate and monitor your temperatures, night time humidity and resulting fan speeds. The
Hybrid Controller is the most stealthy fan controller, with the ability to run fans silently!
It’s also worth remembering a useful lesson from high school, hot air rises, so our exhaust will
ideally be pulling air from the top of the room and our intake ducting pulling fresh, cold air into
the lower expanse of the room. All Quest De-humidifiers will work more efficiently when raised/
roof mounted as warmer air holds more moisture.
A vent fan will pull air much more efficiently than it will push it; try to arrange your fan and
ducting accordingly. Additionally, indoor gardens can often take advantage of existing air-
conditioning, household heating or ventilation systems but be careful of expensive operating
costs for these units!
Once we have installed the exhaust and intake fans our plants should be receiving a plentiful
amount of clean air. Delivering fresh air to plants ensures they will have adequate CO2 to
continue plant growth. An internal air mover and intake fan can assist with providing fresh, CO2
rich airflow. Without CO2, plant growth ceases and a plant is unable to produce the sugars/fuel
for growth and metabolism.
Using a CO2 tank with a regulator and solenoid valve is the most cost-effective means of
improving your larger growroom CO2 levels during the day. Plants cannot use CO2 during the
night, boosting during dark hours is a waste of money, natural resources and can be harmful to
the plant. For tents and smaller rooms, check out the GREENPAD Co2 Generators!
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