Cleaning the loop: Airflow strategies for multi-tier

In 2017, Pipp Horticulture became one of the first manufacturers to offer a purpose-built vertical mobile racking system to indoor cannabis cultivators. For decades, growers have been building and refining the design of single-level grow rooms with HID lighting. However, grow room designs with vertically stacked tiers of benching on mobile carriages were virtually nonexistent. High-efficiency LED fixtures entered the multi-tier cannabis cultivation market around 2015-2017. These LED fixtures allowed for close-proximity lighting with little waste heat and were much more suitable for vertical applications than HID technology. The concept of a vertically stacked cannabis grow room was born, but their designs presented some unique challenges compared to single-level rooms.

Over the last six years, Pipp has installed vertical racking systems in hundreds of facilities worldwide, totaling over 2,500 grow rooms and millions of canopy square feet. Along the way, the company has gained valuable insights into how to design a successful multi-tier grow room and the common challenges to avoid.

By far, the most significant limiting factors to the performance of these rooms are insufficient airflow and poor mechanical system designs. With the proper airflow and mechanical system design, the product quality and yields in these rooms might match or exceed single-level room yields per square foot.

Space Planning and Room Layout
A good airflow strategy starts with space planning and the racking layout within your room. The goal is to create a racking layout that maximizes the canopy footprint within the room while leaving adequate space around the racking structures for air to mix and flow. Without a buffer zone between the racks, you risk “choking” out of the room and restricting airflow. Maximizing the cubic footage of your room too much can be a detriment to plant health.

Plan for at least 6-12” of space between each row and the side walls of the room when the racks are in the resting position (evenly spaced, no mobile aisle). The recommended space in front, behind, and above the racks scales as you increase the number of grow tiers, the racks get taller, and the canopy footprint increases. For example, in a flower room that is 2000-2500 sq. ft of canopy with two tiers of vertical racking, leave 6-8’ in the central front aisle and 2-3’ in the back of the room while leaving as much space above the racks as possible.

Consider the length of your rows and how far the air will travel for a more consistent environment. The longer the air travels, the more humid and hot it will become, resulting in different canopy conditions in the front and back of your room. Generally, 32-40’ or fewer row lengths are preferred to limit air travel distance.

Another important thing to consider is the height of each grow tier. Too short and you can restrict airflow; too tall and decrease the headspace above the racks. On average, most veg rooms are 3-tiers with 4’ tier heights, and flower rooms are commonly 2-tiers with a 5-5.5’ tier height.

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For more information:
James Cunningham, founder
Vertical Air Solutions

Pipp Horticulture
2966 Wilson Drive NW
Walker, Michigan 49534
Tel.: 616-988-4044
Fax: 616-988-4045

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