How To Set Up Grow Room Ventilation System

This guide will teach you the best way to setup a ventilation system in your grow room that will keep you happy throughout the year, while other people are struggling to keep their plants cool.

When you are growing indoors, there are very few things that can have as large of an impact on your grow as the temperature at which you keep your grow room. If you allow too much heat in, it is going to seriously damage your plants. In order to remedy this, it is important to have just the right ventilation system that will keep your grow room cool without costing you an incredible amount of money. This guide will teach you the best way to setup a cooling system that will do the job and keep you happy throughout the year, while other people are struggling to keep their plants cool.

The Perfect Temperature

Most people think that they can just feel and know whether or not their room is too hot, but in fact there is no reason that you shouldn’t have a thermometer to know that you have the perfect temperature in your room. With your thermometer, you can always make sure that the temperature of the grow room is between 75 and 85 degrees F. The absolute hottest that your grow room should ever reach is between 90 and 95 degrees F.


Invest In An Extractor Fan System

The extractor fans are some of the most important parts of your ventilation system, since they will be what pulls the hot air out of your room, allowing you to pump in new cool air. Keep in mind that this fan must be powerful enough to circulate the entire air volume of the room several times per hour, preferably every few minutes.

There is simple math that can help you determine the kind of extractor fan system that you are going to need:

  • For a 23” X 23” grow tent with a 250 Watt HPS system, you will need a 4” exhaust fan and controller. This is the smallest possible fan and grow tent that you are likely to be using.
  • For a 40” X 40” grow tent, use at least a 6” exhaust fan. This is one of the more common sizes that people will be growing in indoors. Again, make sure that you have an adequate controller for this fan.

For a grow room larger than this, add 1” to the exhaust fan for ever foot of room. This general rule can help you know the basics, but make sure to do more research if you are using a hotter lighting system. For LED systems, though, this should be more than enough to keep your rooms adequately ventilated



These exhaust fans will need to be near the top of your room, since we know that hot air rises to the top. Keep in mind that this means that the pipe pushing air into your grow room should be near the floor and it will need to be a bit larger than the exhaustfan that you are using.

Using Oscillating Fans

As for the air that is in your room, it is important that you circulate it around the room in order to reach every single plant that you are growing. In addition to just moving air in and out, you will need an oscillating fan that can blow air between the plants and make sure that they stay cool.

These might not push enough air to cool a room off, but that doesn’t mean they aren’t important. In fact, they serve another purpose in simulating the natural breeze that blows and keeps the stems strong and protects against weak vegetative growth. Use a few 10” wall or floor mounted fans to keep the breeze moving and the air circulating.

Think About CO2 Injection

CO2 injection is important no matter what kind of room or ventilation system you have setup because you will have to make sure that your room not only has the right amount of air in it, but that the air has the right amount of carbon dioxide in it.

By adding CO2 into your room, you will be ensuring not only that your plants have plenty of food to live off of, but you will be making sure that you have harvests that are larger than anything that you might have ever thought possible. In some cases, people have reported up to a 50% increase in yield based off of this one single change in their ventilation system. It is important to place whatever system you decide on on the opposite wall from the ventilation system and place it just over your plants so that the CO2 falls onto your plants, rather than being produced below them.

Control Humidity In Grow Room Using A Dehumidifier

Part of the ventilation system that you might not think about is moving out the humidity that begins to build up when you are growing in an enclosed space. There are plenty of diseases that can grow in a humid environment, so if you want to have ahealthy grow this is definitely something that you should consider. This also has the side effect of causing more resin production, since this is encouraged in an arid environment.

During the different stages of growth there are different humidity levels that you should maintain:

  • During the cloning stage the humidity should be between 80-90%
  • During the vegetative stage the humidity should be between 60-70%
  • During the flowering stage the humidity should be between 40-60%

There are many different types of humidifiers on the market right now, so make sure that you pick the best option for the size of your grow that will control the humidity but also fit into the space that you have available.

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Using The Best Ventilation Systems

When you have the right kind of ventilation system, you can always know that your plants are going to be ok when you aren’t checking on them. Proper ventilation and air circulation are incredibly essential to the safety of your plants and the long term yields that they provide. As long as you are always moving hot air out and moving cold air in you can rest easy knowing that your plants won’t have any health problems that they would typically face in a hot room.

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