You could have the best lights, the best growing system and the best nutrients in the world – if you don’t get your grow room ventilation right then your crops won’t do very well at all. Good ventilation is the key to healthy growing - learn more here.

Heat Problems

If you are growing under High Intensity Discharge grow lamps (Sodium, Grolux and Halide) then you will already know about the heat that these lamps can give out. If left to build up without any kind of forced air exchange in your grow room, this heat can become hazardous to your grow – damaging your plants structure, affecting your plants performance and ultimately reducing your yield. By extracting this hot air out of your grow room using an extractor fan you can create a much friendlier environment for growing plants. Ideally you are trying to create a lights on grow room temperature of between 24oC – 27oC and a lights off grow room temperature of between 21oC – 24oC for optimum plant performance. You can keep temperatures more friendly by drawing air in from indoors during winter (cold air from outside could drop temperatures too far).

Pest Problems

Inadequate ventilation and stale stagnant air provide airborne pests such as fungus gnats or sciarid flies a greater opportunity to infest your grow. By keeping the air constantly moving using oscillating fans or air circulators and by creating a constant flow of fresh air using an extractor fan you can create a less hospitable environment for these pests and reduce your chances of infestation.

Air quality

Your plants need fresh air to grow efficiently. Without going into too much detail, the CO2 content of normal air is around about 0.03% and your plants need CO2 in order to photosynthesise, create energy and grow. Because there is such a low percentage of atmospherically available CO2 you plant will quickly deplete the available gas if you are not constantly replacing the air in your grow room. As a general rule of thumb, you should be looking to replace the air in your grow room at least 20 times per hour to maintain a reasonable air quality.

Humidity

Inadequate ventilation can lead to high humidity, and high humidity can lead to a number of plant health problems at certain stages in your grow. Ideally, you want to maintain a humidity of around 60% RH during vegetative growth (as your plants do not have a very large root system and you want water to be taken in through the leaves) and during flowering you need to reduce this to around 40% RH. The reason you reduce the humidity during flowering is rot. After spending months growing your favourite plants, the last thing you want to find come harvest day are rotting flowers or fruits and very humid conditions are the ideal environment for rot to take hold. You can prevent humidity from rising too high with adequate ventilation. By extracting hot and humid air and replacing it with cooler less humid air from outside your grow room, high humidity will automatically become less of an issue.

So how many fans do I need?

Determining you extraction requirements can be difficult. Basically you need to take care of all of the above factors when buying your extraction equipment. When you are talking about a small grow room, usually one extraction fan to take air out of your grow room and ventilation holes to allow fresh air in. Larger grow rooms will normally also require a smaller extractor fan to force fresh air into your grow room as ventilation holes on their own will not be sufficient in larger spaces.

We recommend using the size and number of grow lights that you have as a guide to what kind of extraction you will need. A full table of fan recommendations is available in the blueprint section of our catalogue which you can request a copy of here.

As a general guide though we recommend:

250 Watt Lights

For 1 x 250 Watt Grow Light:

Output: Either an RVK100A1 or Tent Intake Fan for Extraction

Input: Tent Intake Fan or ventilation holes to allow fresh air in

For 2 x 250 Watt Grow Lights:

Output: RVK100A1 for Extraction

Input: Tent Intake Fan or ventilation holes to allow fresh air in

400 Watt Lights

For 1 x 400 Watt Grow Light:

Output: Either an RVK100A1 or Tent Intake Fan for Extraction

Input: Tent Intake Fan or ventilation holes to allow fresh air in

For 2 x 400 Watt Grow Lights:

Output: RVK125A1 for Extraction

Input: RVK100A1 to allow fresh air in

600 Watt Lights

For 1 x 600 Watt Grow Light:

Output: RVK125A1 for Extraction

Input: RVK100A1 to allow fresh air in

For 2 x 600 Watt Grow Lights:

Output: RVK150A1 or 150mm Futuretech for Extraction

Input: RVK125A1 to allow fresh air in

1000 Watt Lights

For 1 x 1000 Watt Grow Light:

Output: RVK125A1 for Extraction

Input: RVK100A1 to allow fresh air in

For 2 x 1000 Watt Grow Lights:

Output: RVK150A1 or 150mm Futuretech for Extraction

Input: RVK125A1 to allow fresh air in