Published on 24/07/2025
Vincent is a seasoned expert in climate control. With extensive experience as a Climate Specialist, he has travelled worldwide, analysing diverse cultivation systems and crops. In this interview, we asked Vincent to share valuable insights on climate control for cannabis cultivation.
The first step when designing a climate system is identifying crop-specific characteristics. A straightforward description of how the crop will be grown is needed. Factors that must be considered are the planting density, light intensity, transpiration rate, and plant shape.
Cannabis is a compact plant grown at high densities with a lot of light, leading to high rates of transpiration per m2. Once the crop strategy is known, the cultivation system, for example, growing on tables, gutters, or on the floor, must be factored in. The cultivation system plays an important role in climate system design, as it defines how conditioned air is delivered to the plants.
Importantly, the crop’s needs should drive climate system design, not the other way around. If the cultivation system or crop strategy is unchangeable, optimizing humidity and temperature distribution is essential to create a balanced and uniform climate within those constraints.
In cannabis, the most common cultivation systems include growing on tables, gutters, or on the floor. Each system requires a different approach to realize a balanced climate. Each system requires a tailored approach to maintain a balanced climate. The key question is: How will treated air reach and move through the crop?
Still, each system can work if implemented correctly.
When choosing systems, budget is extremely important. Each subsequent step relies on the capacity of a system, which might be capped due to budget. In case of a restriction, it is wise to build the facility in phases. It is better to start optimal but slow, than suboptimal and quick.
Due to the flexibility inherent in growing on the floor, it might be tempting to cover the entire production area with plants, but this can make it difficult for treated air to penetrate the canopy and circulate. As a result, microclimates may form, leading to unwanted side effects like disease pressure. Therefore, the productivity per m2 must be considered using both potential yield per m2 and yield losses due to mildew and botrytis, etc. Table systems face a similar issue in realizing proper airflow around the plants. Additional components like vertical fans might be needed. To realize a homogenous climate, a lot of airflow is required, and the air must be really dry.
With an open crop structure (through increased spacing or growing on gutters), airflow is easier to manage. Air tubes are installed underneath gutter systems to facilitate continuous air movement through the crop. When moisture is constantly transported away, moisture build-up is prevented, and diseases related to stagnant air are more easily tackled. Delivering treated air from below also offers efficient CO2 distribution, rapid climate balancing, and, if properly implemented, lower installation costs.
Reaching a balanced climate is possible with any of the abovementioned systems. However, delivering the climate from below is more precise and efficient. If you want to achieve the same results, would you rather use a cleaver or a scalpel?
Regardless of the delivery method, sufficient airflow is crucial for moisture removal. The key difference between systems lies in the volume of air that must be treated. So, can we quantify the differences?
In the case of a gutter system where the air is supplied from below, values of 150 m3 of air per m2 are common. All of this volume must be treated and moved through the crop. This sounds like a lot, but the air moves only a couple of cm’s per second and the crop is not physically moving.
In overhead delivery systems, the air is mixed with pre-existing heat (sun, lighting installation) and humidity before moving downward through the crop. Consequently, the system must realize extremely low setpoints between 40-50% relative humidity. As a result, overhead delivery systems require significantly more air treatment, between 300-600 m3 depending on the situation. In some cases, these volumes lead to the physical movement of plants due to wind. A larger installation increases costs, making efficiency a top priority.
In large compartments, bringing the climate from below will mean it’s easier to homogenize the climate. With components installed below the crop, they are sheltered from the non-conditioned air. In smaller compartments, however, working with an overhead system can be beneficial, as you will have fewer structural components below the crop.
The most common climate systems we see are the “horizontal” systems. In these systems, cold air is brought in on one side and then blown over the entire length of the chamber to be removed at the other end. These systems are installed in greenhouses, but more often in smaller sections called “cells”. The components of the system are usually placed above the crop. And when steering from above, the installed capacity can be insufficient, and facilities start to add (costly) stand-alone solutions.
A greenhouse had originally installed a climate system where the components were designed to be used in offices. The design incorrectly assumed that warm, humid air would be below the crop and could be easily extracted. In reality, humid air accumulates at the top of the plants, making extraction difficult. After switching to a vertical system, disease pressure dropped, and plants could grow at higher humidities (60-70%). When the facility expands, a climate system based on the vertical approach will be installed.
In a different project, the facility purchased a dehumidifier and placed it in the middle of the greenhouse. The machine worked, but it added heat to the greenhouse. This reduced the chiller’s effectiveness at removing moisture from the air. To compensate, more ventilators were added to stimulate the mixing of moisture and heat. This led to unintended results, as some plants were severely stressed due to the formation of hot zones. This shows that adding more and more systems can negatively impact climate control if implemented incorrectly. After the assessment, we synchronized the machines, significantly improving climate conditions without additional equipment.
It’s crucial to understand the crop strategy when designing the climate system. Cannabis requires a drier climate compared to most other crops. There are multiple approaches to achieve a balanced climate, but think critically about the layout of the facility when choosing a climate system. Set yourself up for success. Start small and expand on a system that works, instead of starting big but unbalanced.
Troubleshoot before adding more systems. Adding new components without understanding existing inefficiencies often worsens climate imbalance. Work with trusted suppliers and specialists who are able to explain their solutions. Always ask why it works for your setup. Previous success stories must be transferable to your situation!
Before constructing a facility, verify the climate system design with an expert. If your system is not performing as expected, reach out for an assessment. We are happy to help optimize your greenhouse environment, both on-site and remotely. Please click here to reach out.