Setting Up the Vent Fan – Step by Step

Marijuana Horticulture

by Jorge Cervantes

Step 1

Figure the total volume of the grow room. Length x width x height – total volume. For example, a grow room that is 10 x 10 x 8 feet has a total volume of 800 cubic feet. A room measuring 4 x 5 x 2 meters has a total volume of 40 cubic meters.

Step 2

Use a vent fan that will remove the total volume of air in the room in less than five minutes. Buy a fan that can easily be mounted on the wall or inline in a duct pipe. Quality inline fans move much air and make very little noise. It’s worth spending the extra money on an inline fan. Small rooms can use a fan that can be attached to a flexible 4 inch dryer hose. Many stores sell special ducting to connect high speed squirrel cage fans with the 4 inch ducting.

Step 3

Place the fan high on a wall or near the ceiling of the grow room so it vents off hot, humid air.

Step 4

If possible, cut a hole in the wall, and secure the fan in place over the hole. Most locations require special installation.

Step 5

To place a fan in a widow, cut a 0.5 inch piece of plywood t fit the windowsill. Cover window with a lightproof dark colored paint or similar covering. Mount the fan near the top of the plywood so it vents air out of the grow room. Secure the plywood and fan in the windowsill with sheet rock screws. Open the window from the bottom.

Step 6

Another option to make a lightproof vent is to use a 4 inch flexible dryer ducting. Vent the hose outdoors, and attach a small squirrel cage fan t the other end f the ducting. Make sure there is an airtight connection between the fan and hose by using a large hose clamp or duct tape. Stretch the flexible ducting s it is as smooth as possible inside. Irregular interior surfaces cause air turbulence and seriously diminish airflow.

Step 7

Another option is to vent the air up the chimney or into the attic where light leakage and door are seldom a problem. If using the chimney for a vent, first clean out the excess ash and creosote. Tie a chain to a rope. Lower the chain down the chimney, banging and knocking all debris inside to the bottom. There should be a door at the bottom to remove the debris. This door is also used as the exhaust vent.

Step 8

Attach the fan to a thermostat / humidistat or another temperature / humidity monitor / control device to vent hot, humid air outside. Set the temperature on 75F and the humidity on 55 percent in flowering rooms and 60 to 65 percent in vegetative rooms. Most control devices have wiring instructions. More sophisticated controllers have built in electrical outlets, and the peripherals are simply plugged into them.

Step 9

Or attach the vent fan to a timer and run it for a specific length of time. This is the method used with CO2 enrichment. Set the fan to turn n and vent out used CO2 depleted air just before new CO2 rich air is injected.