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Ventilation Setup Tips

Proper ventilation is essential to healthy plant growth, and proper filtration is equally essential to clean the air and remove all odors.

Ventilation Setup Tips

Proper ventilation is essential to healthy plant growth, and proper filtration is equally essential to clean the air and remove all odors. You should be replacing the air in your grow space at least every 5 minutes when the lights are on.

To calculate the CFM performance you need to properly ventilate your grow space, use the following formula: (Grow Space Width X Length X Height) / 5 = Recommended CFM.





Please note that CFM performance of a fan is affected by the length and path of ducting and the use of a carbon filter. Therefore when using a carbon filter you must add an additional 20% to the CFM recommendation to account for the loss. So the formula when using a carbon filter would be: ((Grow Space Width X Length X Height) / 5) X 1.2 = Recommended CFM.

Once you have determined the necessary CFM for your space, you can choose what basic ventilation method you will use from the examples below. If you are planning on using air conditioning or plan on adding CO2 into the room to enhance plant growth, you will see the best results with the sealed room and utilizing a fan and carbon filter combo to scrub the air in a closed loop system.


Your ventilation can be set up in a number of ways. Here are some possible configurations:


Ventilation setup guide Note: These configurations will not work with CO2 injection.

Again, keep in mind that the length and path of the ducting used can affect the total CFM performance of the ventilation system, so it’s best to keep it as short and straight as possible.


Dealing With Heat and Humidity

If after setting up a traditional in-line fan and carbon filter setup you are still experiencing temperatures above your desired level (about 78 - 90ºF for seedlings and 72 - 76ºF for mature plants), you will need to turn to alternative methods of removing the heat. Temperatures above 85ºF or below 55ºF will cause plants to be stunted, even if CO2 is being injected into the grow room. It is important to note that humidity control varies in open loop ventilation systems vs closed loop ones. In open loop systems, one option is to directly ventilate the lighting through the use of an “air-cooled” reflector. These reflectors have ducting ports and can be hooked up to standard flexible ducting and ventilated by another in-line fan. By removing the hot air being produced by the lights, you can see quite a bit of reduction in overall room temperature. Air conditioning is another option in extreme heat cases. We carry a number of different air conditioning styles with mini-split being the most popular.

Humidity control is also important in an indoor garden and is most often needed to reduce the overall humidity of the room to about 70-40% depending on the stage of growth. Having a way to control humidity in the room directly with a dehumidifier will make it easier for you to control the growth of your plants and is highly recommended. Dehumidifiers are available at Hydrobuilder.com and act as stand-alone units that do not need additional ducting to operate.

Learn more about tips to deal with heat



Dealing with Odor

While a standard carbon filter will do the job in most cases, some growers may find that it isn’t enough for their particular strain or garden. In these cases you should first check to see that your carbon filter is still usable as the activated carbon that absorbs ordors can be “filled up” and the filter’s odor absorbing performance can go down. Shaking a carbon filter can expose more of the carbon particles that have not been used in some cases. Beyond a correctly sized and fresh carbon filter you can deal with odor by neutralizing it through the use of an Ozone Generator, or via a chemical neutralizer like Ona’s gel based products. All of these methods can be used together or separately as needed.

Learn more about controlling odor



CO2 and other Ventilation Tips

For an in-depth overview of the benefits of CO2 addition for indoor gardens, please see our CO2 article in our Learning Center section. In general you will not want to allow the CO2 you add to your grow room to escape and will need to come up with a method of correctly dealing with heat and odor without venting the air outside of the grow room.

Be aware that ducting can transmit light into an otherwise light-proof grow room if not setup properly. If needed, creating a “u-bend” in the ducting can help to prevent light from getting through the ducting and into your room. Also consider the use of a screen or cover for where your ventilation ducting makes it’s final output from your structure to prevent pests and animals from entering the system and causing potential problems.

Learn more about CO2

Learn more about ventilation


Questions? Call 888-815-9763 or email [email protected].