Grow Room Setup: Ventilation System

When it comes to indoor grow rooms, one of the biggest influences on the plants is the temperature of the room. With too much heat there will be serious damage to the plants, and in order to fix heat problems, you need to make sure your ventilation game is up to par. Below we will guide you through the best way to set up a cooling system that will be reliable for years to come, and won’t break your bank.

Knowing the Perfect Temperature

Some people think that they can tell when a room is too hot just by feeling the air, but there really is no excuse for not having a thermometer. You want the very best for your plants, so why not make sure that you are able to keep the room at the perfect temperature. For most of you out there, a room between 75 and 85 degrees F will be fine, and anything in the 90 degrees and above range is out of the question.

Step 1: Extractor Fan System

In terms of ventilation systems, the extractor fan is basically the heart of the whole operation – this is what pulls the hot air out so that new cool air can be pumped in. The key is to pick a fan that is powerful enough to circulate all the air in the room a couple times per hour, and even more frequently if the room is crowded with plants.

Fortunately, you don’t have to be a wizard with numbers to figure this all out. In fact, there is a simple math equation that helps you choose which fan is best for your setup:

  • For a 23” x 23” grow tent using a 250 W HPS light, you will need a 4” exhaust fan and controller. This is the smallest setup that someone would be using.
  • For a 40” x 40” grow tent you’ll need to step up to at least a 6” exhaust fan and controller. This is a typically sized setup for growing indoors.
  • For grow spaces that are larger than this, simply add 1” to the exhaust fan for every additional foot of room. Keep in mind this is just a rule of thumb and will vary based on how hot your lighting system gets. Systems running LED lights can usually get by with the bare minimum.

The exhaust fan belongs near the top of the room since we all know hot air rises to the top of the area. This also means that the intake pipe (bringing in new air) should be near the floor, and a little larger than the exhaust fan.

What About Oscillating Fans?

So you have cool air coming in from the bottom and hot air leaving at the top, but what about the air that is in the middle? The next step is to make sure that the air is circulating around the room. An oscillating fan will blow air between your plants, making sure they stay nice and cool at all times.

While these fans may not be powerful enough to cool off a room on its own, that’s not really it’s purpose in this situation. The point of the oscillating fan is to mimic natural breezes and push air around the room and plants.

CO2 Levels Are Key

On top of making sure your room has enough air, and air of the right temperature, you also have to make sure the levels of carbon dioxide are just right. CO2 is food for the plants basically, and having low CO2 levels will definitely lead to smaller harvests.

Dealing With Humidity

When growing in an enclosed area there is always be a build up of humidity, regardless of how awesome your ventilation system is. Never underestimate how easily diseases can grow in a humid environment – keep your humidity levels in check.

  • Cloning stage: 80-90% humidity
  • Veg stage: 60-70% humidity
  • Flowering stage: 40-60% humidity

When shopping for a dehumidifier, focus on finding a unit that can handle all the air in the room and also fit someone where in the room.

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