Indoor Grow Room & Tent Ventilation 101
Having regulated grow room ventilation ensures that your cannabis plants grow in an optimized environment with temperatures and humidity that allow you to grow the most potent buds. Having insufficient airflow through your grow room negatively affects both yield and quality.
In an indoor environment, plants do not have access to the same sort of fresh air as outdoor plants. Ventilation is at the core of ensuring that the air in your grow tent promotes healthy growth. Good ventilation allows plants to have access to the fresh air required for photosynthesis. Additionally, ventilation helps maintain other indoor air quality factors, such as humidity, temperature and CO2.
Why is grow tent ventilation so important?
The most common grow room systems use a combination of exhaust fans and ducts or pipes to maintain airflow. And circulation fans are used to keep the air flowing within the room.
Like all other green plants, cannabis transforms light energy into chemical energy through a process called photosynthesis. If a cannabis plant does not get enough CO2, it will continue to grow until its stored sugars are depleted. Once that happens, its metabolism decreases, and it will stop growing. On the other hand, if a plant gets too much CO2, it will slow down or even stop photosynthesis. The trick is finding the right CO2 level for a grow space to maximize photosynthesis and yield.
Optimal CO2 concentration
To obtain growth equivalent to outdoor plants, CO2 concentration should be around 400 ppm in an indoor space with normal fresh air ventilation.
Plants are natural humidifiers, so it only makes that a room full of them will require some sort of humidity regulatory tool. Humidity in the grow room is largely a result of transpiration. Transpiration is the process by which the leaves of the plant give off water to the atmosphere. Much like a straw, the suction created by transpiration pulls nutrients up through the roots as the plant produces water vapour.
In the presence of too much humidity, there is a greater chance of attracting insects and other unwanted pesticides. Along with the excess heat, a ventilation system also dumps out the excess moisture in the air. The dry air takes away some of the water from the upper parts of the plant, forcing the plant to absorb more water through the roots, helping the plant absorb more nutrients.
Stagnant or humid air harms various factors in a grow room, including the topsoil. The medium will remain damp or humid in the room of stale air, attracting fungi, mould, mildew and insects. A healthy level of dryness in the topsoil because of a steady supply of dry air helps slow down the growth of pest populations.
Types of ventilation in a grow room
Passive vs active intake system
Passive intake uses natural airflow and negative pressure to bring air into the room. Basically, there is a hole or vent in the grow tent that passively allows air to enter. It does this through pressure differences inside and outside the room. This is like if you opened a window to let in air.
Active intake pulls air into the room with a fan. This actively draws in air to ensure high levels of circulation. The size of the active fan doesn’t matter as much as the air pressure blown in. You should use an active fan that pulls in at least the same pressure rate (and CFM) as the exhaust fan.
Carbon Filter help with odour
A carbon filter helps remove the odour from a grow room. A good-quality carbon filter is connected to an extraction fan. The fan pulls air through the carbon filter. As this happens, the activated carbon inside the filter chemically absorbs the terpenes (and other aromatic compounds), locking them inside the carbon filter. The fan then pushes the cleaned air out.
If you are wondering whether your fan should pull or push the air through a carbon filter, in most grow rooms and tents, the carbon filter is installed first while the fan is pulling the air outside. With this setup, aromatic molecules along with dust and other unwanted VOCs get efficiently filtered and to avoid damage the fan or accumulation in the duct. However, if you are limited on space and cannot fit your carbon filter inside your set up, you are still able to mount the fan on the wall of the tent or room and while air is forced through the filter placed outside. Although not ideal, but acceptable.
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