Indoor Gardening-Step 2-Air Control
Air Control has a direct impact
on temperature, humidity, and CO2
The quality and control of air in the growroom is an important
but often overlooked factor. Next to lighting, the aerial
environment is the most influential factor affecting plant growth.
The most efficient way to control air quality is with an exhaust fan pulling
air out of the room. The exhaust fan can be supplemented by an intake
fan pushing air in the room.
An exhaust fan will pull air out of the room and naturally draw fresher air
into the room through intakes, cracks and doorways.
How big of a fan do I need?
The size of fan needed is determined by the size of the room and the number
of lights in the grow area. Generally, the fan should be able
to change the air in a room every 3-5 minutes.
Exhaust fans are rated by CFM(cubic feet per minute). Simply
divide the volume of the grow area by the number of minutes you want to completely
change the air.
E.g. Size of fan =Volume of grow area / number of minutes to
exchange air
Size of fan=(lxwxh)/3
The more lights running in one room the more rapidly you want to exchange
the air.
A 400 watt growroom should use a 130 CFM to 265 CFM fan under normal
conditions.
A 1000 watt growroom should use a 265 CFM to 465 CFM fan under normal conditions.
Multiple 1000 watt setups require a fan from 465 CFM to....?
If you are having a problem getting fresh air into the room then use a fan
that will push air into the room. Small intake fans are ideal for providing
cooler, fresher air into the room.
What do I need to know about the temperature?
Generally, the ideal temperature for plant growth is 72 degrees fahrenheit.
At this temperature photosynthesis and respiration occur at the same rate.
Keeping the temperature at 72 F can be a challenge in multiple light growrooms.
A good rule of thumb : If you are comfortable in the growroom then
your plants will most likely be too.
Hint: Try and keep temperature under 80 Fahrenheit.
What do I need to know about relative Humidity?
The lower the humidity, the more water and nutrients plants will draw
throught the roots. Conversely, a higher humidity will slow the
respiration rate (the drawing up of water and nutrients) and create an environment
where mould and mildew can form.
A good range for relative humidity is 40-60%. Below 40% relative
humidity plants can become dehydrated and slow growth.
A steady humidity level promotes healthy growth.
Hint: It is better to keep humidity lower than higher to avoid mould
and mildew.
What do I need to know about CO2?
The CO2 level in the atmosphere is usually around 300 ppm.
CO2 ,in conjunction with high light levels(50-60 watts per square foot),
will increase the rate of photosynthesis. Through adequate ventilation
(a large exhaust fan) a growroom can maintain a steady level of CO2 for
the average grow setup. Plants grown under high light levels can utilize
up to 1200-1500 ppm of CO2.
Hint: Use a large exhaust fan to keep CO2 levels steady. Do not
bother using CO2 injection or burning systems until all other plant growth
factors have been optimized. Use circulating fans to move air around
as CO2 is heavier than the ambient air.
What about air circulation?
An oscillating fan can provide the necessary air circulation within a growroom.
Proper air circulation aids in mixing the warmer air near the ceiling with
the cooler air near the floor. The mixing of air also helps to
prevent insect and fungus problems, moves CO2 around the room,
and strengthens the plant by providing constant air over the leaf stomata.
To shop for exhaust fans
click here!
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