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Mastering Air Circulation in Greenhouses: Insights from John Juhler
Optimizing Greenhouse Microclimates: A Guide to Effective Air Circulation
Corenthin (Félix) Chassouant
March 26, 2025
Maintaining optimal growing conditions is paramount in greenhouse cultivation. One of the most critical factors in achieving this is proper air circulation. In this edition of Horti-Gen Insights, we delve into the intricacies of managing airflow in greenhouses, drawing from the expertise of John Juhler from Vostermans Ventilation for North America. We'll explore the differences between Horizontal Air Flow (HAF) and Vertical Air Flow (VAF) systems, their impact on greenhouse microclimates, and best practices for implementation.
A special thanks to John Juhler with Vostermans Ventilation for his expert feedback.
What We Are Covering Today:
Air Renewal vs. Air Circulation
Air renewal involves exchanging indoor and outdoor air to control temperature, humidity, and CO2 levels, typically using ventilation systems. In contrast, air circulation focuses on mixing air within the greenhouse to ensure uniform conditions, often achieved with HAF or VAF fans.
While air renewal affects overall climate and CO2 levels, air circulation influences the microclimate around plants, promoting healthy growth. Both processes are crucial for maintaining optimal growing conditions in commercial greenhouses.
The HAF vs. VAF Debate: Choosing the Right System for Your Crops
When it comes to greenhouse air circulation, growers often decide between HAF and VAF systems. Each has its unique advantages and applications.
HAF fans operate on the principle of horizontal momentum, circulating air across the greenhouse floor. Over time, this horizontal movement can help with temperature destratification. On the other hand, VAF fans draw air from the floor level up to the fan, mixing cooler floor air with warmer air at the top of the structure.
The choice between HAF and VAF often depends on the specific needs of your crops and greenhouse setup. VAF systems create a more normalized air temperature inside the structure while improving the overall climate, potentially outperforming HAF in specific scenarios.
In some cases, VAF and HAF can be combined in a greenhouse to achieve optimal climate uniformity when dealing with tall structures or multi-level growing systems, as VAF fans can address vertical temperature gradients. In contrast, HAF fans ensure horizontal air mixing.
Optimizing Fan Placement for Uniform Climate Control
Proper fan placement is crucial for achieving uniform temperature and humidity levels in greenhouses. HAF and VAF systems have unique airflow patterns contributing to this goal2.
HAF Systems: The 'Racetrack' Effect
HAF systems typically move larger air volumes in serial ('racetrack') or parallel configurations. In a serial setup, fans are arranged to move the air mass in alternating directions, promoting thorough mixing. Parallel configurations, often used with pad/fan cooling systems, move the air mass in one direction for quicker temperature control.
VAF Systems: Vertical Circulation
VAF systems use fans in conjunction with each other to create a vertical recirculation pattern. This approach mixes stratified air with a subtle airflow. When the application is suitable, growers of certain plants report improved results with VAF systems.
VAF systems are crucial in preventing tip-burn in leafy green greenhouse cultivation. VAF fans effectively reduce the boundary layer around leaves by directing air downward onto the crop, enhancing transpiration and calcium transport to young, developing tissues. This vertical airflow helps maintain uniform temperature and humidity levels, significantly reducing tip-burn risk.
Both systems provide air movement across plants, helping to remove humidity and condensation while regulating temperature. The choice between HAF and VAF often comes down to the specific requirements of your crops and greenhouse layout
Mitigating Common Greenhouse Issues Through Active Ventilation
Active ventilation systems like HAF and VAF are crucial in addressing common greenhouse challenges such as high humidity, condensation, and temperature fluctuations.
Air movement around plants can significantly improve humidity control by removing saturated air near the leaves and replacing it with drier air. This process encourages plant transpiration while preventing moisture accumulation that could lead to disease.
In contrast to facilities relying solely on natural ventilation, greenhouses equipped with mechanical ventilation or circulation systems have a reliable source of air movement. This consistency is especially valuable when atmospheric conditions or weather patterns are unfavorable.
Energy Efficiency and Automation: The Future of Greenhouse Climate Control
As energy costs continue to rise, growers are increasingly focused on optimizing the energy performance of their ventilation systems. Vostermans Ventilation offers fans in various voltage configurations, including 1/120v, 1/240v, 3/460v, and 3/230v. Generally, 3-phase and 1/240v systems consume about half the power of 120v systems, making them more energy-efficient.
Advancements in fan control equipment have revolutionized greenhouse climate management. Modern greenhouse control systems use sensors to monitor temperature and humidity, automatically adjusting ventilation equipment to maintain desired conditions. These systems can be tailored to account for regional climate variations and specific plant growth cycles.
Innovations in HAF and VAF Systems: Enhancing Greenhouse Air Circulation
As technology continues to advance in Controlled Environment Agriculture (CEA), Horizontal Air Flow (HAF) and Vertical Air Flow (VAF) systems are poised for significant improvements. These innovations aim to enhance greenhouse operations' efficiency, precision, and sustainability.
AI-Driven Climate Control
Integrating artificial intelligence (AI) into HAF and VAF systems is one of the most promising developments. AI can analyze real-time environmental data to adjust fan speed and direction, ensuring optimal air circulation based on specific crop needs. Predictive algorithms can anticipate temperature and humidity fluctuations, allowing fans to adjust airflow patterns for better climate control proactively.
IoT Integration
The Internet of Things (IoT) is also transforming air circulation systems. Networked HAF and VAF fans can communicate with each other to create coordinated airflow patterns, ensuring uniform conditions throughout the greenhouse. IoT sensors provide detailed data on microclimates, enabling precise fan control and minimizing energy waste.
Robotics and Automation
Automation is another area of innovation. Automated systems can adjust fan positioning based on crop growth stages, and mobile robotic units can supplement fixed HAF or VAF systems, providing targeted air circulation where needed. These advancements promise to revolutionize greenhouse air management, offering growers unprecedented control over their growing environments while prioritizing sustainability and efficiency. As these technologies mature, they will play a crucial role in shaping the future of CEA.
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Conclusion
Adequate air circulation is a cornerstone of successful greenhouse cultivation. By understanding the nuances of HAF and VAF systems, optimizing fan placement, and leveraging modern control technologies, growers can create ideal microclimates for their crops while maximizing energy efficiency. As greenhouse technology continues to evolve, staying informed about the latest advancements in air circulation will be crucial for maintaining a competitive edge in the horticultural industry.
Future innovations such as AI-driven predictive climate control, IoT-enabled fan networks, and automated robotic air circulation systems hold great promise for further transforming the landscape of greenhouse cultivation.
Complementary sources:
University of Connecticut: Horizontal Air Flow Systems
https://ipm.cahnr.uconn.edu/horizontal-air-flow-systems/
University of Waterloo. Published in March 2024: Case Study: Controlled Environment Agricultural (CEA) Systems. https://uwaterloo.ca/disruptive-technologies-economic-development/sites/default/files/uploads/documents/cea-systems_case-study-10may2024.pdf