Many modern farmers are turning to sealed greenhouses over traditional ventilated greenhouses. Heavy ventilation is required daily to combat overheating in your typical traditional greenhouse. When growing in this type of greenhouse, the goal is often to try to exchange the entire air volume inside the greenhouse every minute through the use of enormous exhaust fans. In greenhouses that provide supplemental CO2, exhaust fans continually exhaust warm, CO2-rich, and odorous air. Apart from increasing the risk of pests and pathogens, many territories prohibit exhausting untreated, odorous air outside. By keeping the conditioned air inside, sealed greenhouses can provide a solution to these problems.
Advanced climate control systems can take the place of ventilation by regulating the temperature and humidity of the sealed environment to maintain precise growing conditions for the plants. The sealed nature of these greenhouses also provides benefits such as pest control, energy efficiency, odor control, and pollination prevention.
Pests and pathogens wreak havoc on all commercial crops, indoor, outdoor, and greenhouses, which is why IPM (integrated pest management) is a large part of modern farming. A sealed environment can drastically reduce the chance of outside infection that would otherwise be brought in via air exchange. The same can be said for cross-pollination prevention. Certain crops, such as cannabis, are extremely sensitive to being pollinated from outside sources, for example, a neighboring outdoor hemp farm a few miles away. In addition to not having ventilation, positive pressure is often utilized to help combat the above by ensuring outside air does not come inside whenever doors are opened.
Modern sealed greenhouses are commonly constructed using building materials with much greater insulation properties which help to keep the climate regulated throughout the year. This is beneficial for energy efficiency, maintains cooler air in the summer and warmer air in the winter, and has a major impact on plant health. Plants subjected to inconsistent environmental parameters must spend more energy adjusting/adapting to the ever-changing climate rather than utilizing that energy for healthy growth and development in a stable, stress-free environment.
Speaking of stable climate, CO2 is often supplemented in commercial grows to obtain the most plant productivity. With a sealed environment, CO2 levels can be maintained consistently instead of constantly varying each time air is exchanged, not to mention all the CO2 wastage prevented.
While odor control is not a big factor for crops other than cannabis, it is on the forefront of the radar for cannabis growers in certain regions with laws prohibiting the exhausting of untreated air outside due to odor. If this applies to you, a sealed greenhouse may be the only way to go unless you plan to rely on carbon filtration, which needs to be replaced every few months, thus adding extra labor and cost.
Sealed greenhouses offer many benefits over traditional greenhouses. However, there are some setbacks to be aware of, such as the increased need for adequate HVAC, dehumidification, and the overall increased up-front cost. Because a sealed greenhouse is essentially a large indoor grow with assisted natural lighting, so adequate cooling must be planned. Whether with a traditional HVAC system or an evaporative/ hydronic cooling system, adequate cooling must be accounted for to prevent overheating due to lack of ventilation. Additionally, being a sealed greenhouse, excess humidity is expected due to the water vapor that evaporates from leaves during photosynthesis. Without adequate venting, this water has no place to go; thus, adequate dehumidification is needed in order to prevent the growth of mold/pathogens.
The upfront investment required for an automated greenhouse is typically higher than a traditional ventilated greenhouse. Fortunately, thanks to the advanced automation systems available today, such as Growlink, less labor and energy input is required, thus making the greenhouse more efficient overall, lending to a faster ROI. If you can afford the increased upfront cost, the benefits offered by sealed greenhouses outweigh the potential downsides.