How to vent a grow room

Written by colleen collins
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How to vent a grow room
One of the more important aspects of a grow room is good air flow. (fan image by Antons Matvejevs from

One of the most important aspects of a grow room is good air flow. Consistently refreshed air promotes plant growth and prevents problems such as heat-related stress on plants, mildew and insects. Venting a grow room includes such tasks as calculating the room volume and fan sizes, adjusting the fan sizes for any air flow restrictions and setting up the fans.

Skill level:

Things you need

  • Intake fan
  • Exhaust fan

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  1. 1

    Calculate the room volume. Measure the length, width and height of the grow area, then multiply these three numbers to calculate the room volume. For example, if a room is 10 feet long, 8 feet wide and 12 feet high, the room volume is 960 cubic feet (10812).

  2. 2

    Calculate the fan size. A cubic feet per minute (CFM) number represents the amount of air a fan moves in one minute, minus any restrictions to the air flow. A general recommendation is if your grow room is in a hotter climate, refresh the air every minute; for a cooler area, refresh up to every three minutes. For example, if your grow room is 960 cubic feet and you're located in a cooler area, select a 320 CFM fan (960/3).

  3. 3

    Adjust CFM for any restrictions to air flow. The calculations in Step 2 are for air flow with no restrictions. If a 320 CFM fan is connected, for example, to a carbon filter tube, add 20 per cent to the fan size, and if your grow room is in a hot, humid climate, add 40 per cent. When selecting a fan CFM, keep in mind it's better to have more circulating air than not enough. For professional suggestions on CFM fan sizes for a grow configuration, consult with a hydroponics store.

  4. 4

    Set up the fans. Keep in mind that hot air rises and colder air settles. Therefore, mount one fan higher inside your grow room to blow the heated air out (for example, through a window or hole in the wall to the outside). Mount another fan outside the room to blow cool air into it.

Tips and warnings

  • If you'd like to be less hands-on, consider automating the room ventilation with a timer that turns on the fans at certain times throughout the day.

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