Just like the lighting system or the nutrient solution, a correct ventilation is one of the most important parameters to take into account when growing marijuana indoors. A proper air ventilation allows the plants to perform all the needed gas exchanges, along with evacuating the heat produced by the lamps, achieving a better climate control and thus growing stronger plants. Proper ventilation is connected to humidity and temperature. It prevents things like mold, fungi, and other unhealthy issues from developing on your plant. You need to consider the size of your growing space and the amount of plants you will be growing. The greater the number of plants, the more important it is to have good ventilation.
The reason for ventilating a grow room is simple; cannabis plants need fresh air. Therefore, every grow-op requires air exchange. That means cool, fresh air in, and stale, hot air out. A lack of proper ventilation can cause the pores in the leaves of your marijuana plant to start to clog. When this happens the leaf will eventually die and fall off. If there is too much leaf death, eventually your plant itself could die. The plant’s leaves are responsible for absorbing the energy of the sun and using it for faster and better growth. Therefore, less leaves means your plant will be losing some valuable resources.
The lights you choose and the size of your grow space will dictate the type of ventilation system you must utilise. Having good ventilation from an early age of your plant has the additional benefit of encouraging it to grow a thicker stalk, as it registers this as potentially harmful wind and therefore grows stronger to counteract it. The thicker and stronger your plant is, the better the end product.
The ventilation systems normally used are composed of, at least, two or three complementary elements: the air extractor, an interior fan that moves the air of the growing space and, in most cases, an intractor fan.
The extractor fan is the key element of any air ventilation system, as it renews the air and regulates the climate of the growroom. The needed extraction power depends on both the growing space and the lighting system used. The more light output we use, the more potent the extractor fan must be. It is important to distinguish between conventional inline extractors and industrial fans which are industrial turbines much more efficient than the former. In practice, inline fans should only be used when growing with energy-saving lamps and perhaps also as air intractors, as we’ll see next. If you are using HM or HPS bulbs, industrial extractors are highly recommended. This type of extractor also allow to attach carbon filters to remove indiscreet odours from the plants.
In smaller spaces, the intractor fan may not be necessary if we have a good extraction system (RVK, Prima Klima). Indeed, thanks to the effect of the pressure, the air will passively enter the growing tent through the holes on its sides.
Of course, using an intractor fan is recommended:
- To renew the plants environment with fresh air from another room or the outside, improving the climate of our growroom.
- To limit the air pressure caused by the extractor, that tends to “vacuum” the walls of the growing tent, thus reducing the available space.
In all cases, the airflow capacity of the intractor must always be lower than the extractor capacity, specially when using carbon filters (thanks to the pressure all the odorous air passes through the filter). Generally, a simple inline fan will work perfectly as intractor. Your intake fan needs to be positioned near or at ground level to connect to the hole in the bottom corner of the grow tent.
The interior fan is important specially for the health of the plants, since it acts as the wind does outdoors and causes:
- Stronger branches and stems, which become more resistant and capable of supporting the weight of the buds at the end of the flowering stage.
- Better air renewal inside the growing space, enhancing gas exchange.
- Decreased relative humidity levels, with less diseases and pests.
When the lamps are off and our plants have their night period, we can decrease the airflow since there won’t be any need to reduce the temperature produced by the bulbs and the plants need less air renewal during this period. To do so, we can either reduce the power of the extractor fan using any kind of controller, or use timers to reduce the operating time of the fans, for example using them 15 minutes every hour.
Never stop the air extraction system completely for some hours, since plants always need a minimum air renewal to ensure a correct respiration.
The end of flowering is another crucial stage; decreasing the power of the air renewal system during this period will surely promote mold growth. During this stage, we recommend to use all fans and extractors at full power, 24 hours a day.