Indoors Cannabis Ventilation

Is Cannabis the next green gold?

Along the last years we are witnessing the progressive decriminalization of this crop and its by-products; scientific dissemination and specialised press bombard us on a weekly basis with the multiple benefits of that so-called panacea named hemp and most of the countries are working, to some degree, on any normalisation of both production and use.

In fact, just few crops can be found at this level of profitability and where cutting-edge technology is so worth it. Even fewer where ventilation is such a crucial primary production factor.

Commercial production 
Intensive cultivation of hemp is typically indoors, so environment can be controlled and adapted to the particular needs of these plants; indoors meaning both greenhouses or cleanrooms, depending on the location climate conditions. There are good reasons for this: from the one or two crops feasible from outdoor conditions, up to six harvests per year are reachable indoors, ten times more production per hectare.

Greenhouse is economically more profitable, especially in equatorial areas with more than 10 hours of sun light a day. Modern cultivation incorporates a wide variety of systems, from traditional soil to hydroponics and aeroponics; even earth is expendable, ventilation is not. These plants are extremely sensitive to air circulation and exchange and only professional ventilation engineering can make them reach optimum performance.

Every fan-involving equipment will be found in these kinds of installations: air cooled shades, air conditioning or refrigeration devices, intake and extraction units sometimes involving silencers, carbon filters, CO2 and ozone generators, nebulisation or dehumidification systems and recirculating fans for destratification. Nothing closer to an amusement park for a fan manufacturer! When, further to fans, the concept includes control, monitoring and smart automatization, the value added, the business opportunities are boundless. The chances do not end there, though. Once harvested the crop needs to be trimmed, dried, cured before moving onto the corresponding industrial process, depending on the final destiny. Once again, efficient ventilation is essential in every one of the former processes; it makes the difference to processing cycle and preservation times, plus the impact on energy consumption.

The real question is: will any fan do?

Ventilation in intensive Cannabis cultivation 
This crop has two types of conditioning factors. Those related to growth: fertigation, lighting and environmental balance (temperature-relative humidity-CO2); and those related to the variety selection.

The role of ventilation is very interesting here, showing dichotomous relationships with the conditions above:

•    Fertigation is the system that works best here, whether on substrate or hydroponics: Water should never lack; in case of substrate, it should always be wet, but in both cases irrigation come together with ventilation. Air movement underneath the root level is one of the best ways to achieve this effect. At the same time, these roots grow better and more robust.

•    Cannabis is one of the commercial crops that makes the best use of light, in an enriched CO2 atmosphere and with the right intensity and spectrum for each stage of development. However, these lights involve heat sources that should be eased and distributed by adequate air recirculation.

•    Finally, the environmental factor is essential in all cases. An inappropriate temperature-humidity balance defines every crop profitability, limits vegetative development and flower production, reduces the production quality and encourages health problems. Cannabis is quite vigorous, reaching its highest levels of photosynthetic efficiency at relatively high temperatures
and humidity. These optimal daytime conditions bringing along an immediate danger as soon as night falls, the temperature drops and the air may not retain all the moisture it contains, so condensation occurs. Most fungal and bacterial situations happen in a sheet of water on the surface of the plant. This particularly frequent scenario can be avoided with a properly
dimensioned air recirculation system which regulates that hydrothermal balance. This recirculation also cleans and homogenises the gaseous horizon around the plants, especially at the points of maximum CO2 demand (high photosynthetic activity).

Now, talking pest control, the most versatile, economical and accessible measure to prevent phytosanitary problems is to ensure proper ventilation. Adequate and sufficient air movement reduces or even eliminates potential water condensation on the crop surface, while complicating the movement of insects. Last but not least, it increases the resistance of the plants, which results in a drop of extreme events incidence. Of course, it is essential to observe precise control of air velocities on leaves and plants; too high values would lead to stomata to close and the interruption of photosynthetic activity.

Again, the case of Cannabis is particular because the GACP (“Guideline on good Agricultural and Collection Practice” by the European Medicines Agency, 2006) expressly states that the application of pesticides and herbicides should be avoided as far as possible, so focus on prevention.

In conclusion, the ventilation of intensive Cannabis cultivation, whether in greenhouses or in a vertical cultivation room, must consider three independent but complementary and balanced systems:

1. Air renewal, observing ratios above the usual values for horticultural crops and considering sub-radicular systems.

2. Air recirculation, for an adequate destratification and balancing of the environmental conditions.

3. Gentle ventilation directly over the plant, to stimulate its development and resistance and prevent health problems.

Very often we see typical domestic oscillating systems trying to cover at the same time destratification and direct ventilation on the plants and achieving, I am afraid, neither of them.

In conclusion, ventilation is key to any intensive growing room or greenhouse; for Cannabis it makes a difference whether an adequate profit, usually well above any horticultural crop, or a nightmare of constant infections, underproduction and certification problems in the case of medical cannabis.

Let us introduce you to the Cannabis real ventilation! 

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