Ventilation Systems Explained

This help file is intended to give you a better understanding of the various ventilation systems that are required to create a good growing environment for your plants. When growing hydroponically or in any artificial indoor environment it is absolutely critical to success that you put in a suitable ventilation system which would include one or all of the following:

1. Main extraction fan

Still air in a grow room is not a good thing as the plant needs fresh air at all times to maximize its potential growth. At the very least you must always use a suitable main extractor fan for ventilating your grow room.

The job of the main extractor is to remove heat from your growing environment and to change the air so your plants can breathe. To remove heat effectively the main extractor should be set up to remove air from the hottest areas. Following the principle that hot air rises run ducting or hang your carbon filter high up in the room just beside or above your lighting. And if possible run your lights overnight so they are not on at the potentially hottest parts of the day. Make sure that all your extracted air is finding its way outside somehow because you don't want to recirculate the used air.

-- Extraction Fan Calculator --

To decide what fan you need for ventilation click on the link above and input 20 changes per hour.

2. Fan Speed Controllers

The trick with using extractor fans is that you are always striking a balance with removing heat against removing too much air which can stress your plants. Its scientifically proven that more than 24 changes of air per hour will begin to stifle your plants development, you may have noticed this if your plants closest to your extractor go a bit yellow or worse.

This said there are times especially in summer or on very hot days when you want to ignore this as the excessive heat buildup in your grow room would do more damage.  The best solution to these problems is to use a fan that's a little more powerful than you need and employ a fan speed controller. The controller works by increasing the speed of your fan if it gets too hot and reducing the speed of the fan if it gets too cold. You get the best of both worlds extra cooling on hot days and quiet fans when your lights are off. A dial on the front of these units allows you to select a temperature that the fan controller will do its best to maintain.

3. Intake Fan

For ventilation systems in rooms with multiple lights we would suggest using an intake fan in conjunction with your main extractor fan to guarantee you're getting enough fresh air into your room. Set intake fans up so they put the air in at the lowest level possible and if your room is quite large consider splitting the intake to put air in at multiple locations. When selecting an intake fan it needs to be about a third as powerful as your main extraction fan.

HINT: One benefit of using an intake fan is that you can choose where you're taking that air from by where you place the ducting so if you have a nice cool room (15-20 degrees) you can pull the air from do so. This will give your ventilation system a head start.

Last Updated: July 08, 2008