By Nickolaus J. Sanchez
Most all indoor growers would agree that the total environment is the
final result of all your grow room efforts. Whether you are in a small closet,
a bigger tent, or a full room; if your total environment isn’t kept up to good
standards, your plants will struggle. So far, we have covered the basics for
maintaining your lights, soil, and water. The next step for realizing the total
environment is to create essential air flow and ventilation, for the plants to
dance.
Much like humans, plants need fresh air to
survive. The major difference between us is
that plants inhale carbon dioxide and exhale
oxygen. Plants also have “lungs” or “pores”
like humans called stoma (plural: stomata),
which are found on the underside of the
leaves. Without efficient air flow these stomas
can’t breathe, which will result in a very sad
plant. It’s important to remember that when
growing indoors you want to imitate nature
as much as possible. This means making the
room’s air feel like you are walking through a
nice breezy forest of Northern California in the
middle of Spring.
So you might be asking yourself, “How do I
create such an environment?”
To create an outdoor effect indoors, fans
are required. Circulating the air will not only
allow the plants to breathe, but it also allows
the air to move around the room so no
stale pockets occur. In addition, setting up
fans that encourage your girls to sway in the
wind is very necessary to building trunk and
branch strength. If you are in a small closet
or a small tent, you could get by with one
or two small, 6” clip fans (as long as all the
plants are moving evenly). In a larger area,
like a room, a few oscillating fans should do
the job. Remember the stomata are on the
underside of the leaves so aiming air movement
from both the bottom and top of the
plant is optimum.
Now that you have air circulation set up,
the next thing to do is to set up the air ventilation.
As mentioned above, fresh air is
essential for healthy plant growth. *In order
to exchange air in your grow space a vent,
that allows fresh air in situated towards the
ground, and another vent, that releases
the stale air situated towards the top, are a
requirement. An inline fan will be attached
to the top vent to suck the stale air out. This
creates the vacuum that pulls the fresh air
in down below. Selecting your inline fan
depends on the size of your grow (including
cubic volume, plant count, fixtures, circulation
fans, etc.).
Inline fans come in different sizes and ratings.
The bigger the opening size, plus the
motor power, the bigger the rating. Inline
fans are rated in cubic feet per minute
(CFM). So a 4” fan rated at 171 CFM will
exchange 171 cubic feet per minute. Most
4” fans will be about 160 CFM, 6” fans will be
around 450, and 8” in the ballpark of 720.
Choose a fan with a CFM rating higher than
the volume of your space to create proper
negative pressure. For example, a 4’x4’x6’
tent is 96 cubic feet (which would require
at least a 4” 100 CFM fan). In a larger room,
like 8’x8’x8’ with a volume of 512 cubic
feet, an 8” 720 CFM would be more than
enough. In a basic grow, having this negative
pressure alone will do, however, an air
exchange of every cubic foot every 5-10
minutes is most efficient. See side bar for details.
Also, to create negative pressure, fans
should always be set up to pull air out rather
than push air in. Some larger grows will require
a fan to push air in along with another
fan pull air out.
The next question to ask yourself is if your
lights put off heat? If so, are they air
cooled? When growing with a light like an
LED or a fluorescent T5, ventilation should
be a lot easier for a beginner because they
don’t put off a lot of heat (which, in turn,
doesn’t require air cooling).
The opposite is said for High Intensity Discharge
(HID) lights like High Pressure Sodium
(HPS) and Metal Halide (MH). HID
lamps are used either with an open hood
or a closed, air cooled hood. The Trifecta
setup mentioned in 102 features an open
hood that doesn’t have any air cooling. In
the winter this light works perfectly, considering
it also acts as a heater. In the summer,
it’s best to use an air cooled HID. If
you do use an open hood in the summer,
you will most likely need to also employ an
air conditioner. This will not only help with
any heat buildup, but adds more circulation
as well.
Air cooled hoods have a removable glass
lamp cover with an entrance and exit
hole on both ends of the hood. This will allow
for the ventilation ducts to be hooked
up to the light, that way the heat from the
light isn’t dispersed inside, but instead pulled
to the outside of the garden. The only thing
that changes is; rather than the room’s air
exiting straight through the fan, it now passes
through the light housing first.
The final step in this process is setting up the
air cooling system, which is fairly simple. First
you are going to connect heat resistant
ducting from the light to the exhaust fan.
Ideally, you want the fan and the entrance/
exit holes of the light to be the same size,
especially if you have more than one light.
However, if your light and exhaust fan aren’t
the same size, for better air flow you want
the ducting to match with the bigger size
of the two. You will also need to purchase
an adapter so the ducting will attach to
the smaller size. If you have more than one
light, connect the lights to each other with
the ducting until they are all connected to
the fan. The rule of thumb here is three lights
maximum for one fan. If you attach more
than three lights per fan, your air ventilation
becomes poor. Also, always be sure
that your ducting is as straight as possible
because the more bends you have, the less
efficient the air flow.
Remember that air circulation and ventilation
not only make the plant healthy, but
happy too. As I mentioned earlier, it’s important
to imitate nature because plants
evolved outdoors. So creating that simulation
will put them in good mood, which will
result in a better harvest.
