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Optimizing Grow Room HVAC | The Ultimate Guide for Cannabis Cultivation

Learn how to create a more efficient and profitable grow room by improving your HVAC system


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As a facility manager or business owner, you understand that the success of your cannabis crops hinges on many factors.


One of the most critical, yet often overlooked, is the role of your HVAC (Heating, Ventilation, and Air Conditioning) system.


Did you know that optimizing your HVAC system could significantly increase your harvest yield?


That’s right, a well-designed and maintained HVAC system can lead to healthier plants, higher quality products, and ultimately, increased profits.


Whether you’re looking to prevent disease, improve product quality, or increase your bottom line, this guide will provide the information you need to make informed decisions about your HVAC system.


Let’s grow together!

 

Understanding the Basics of HVAC in Grow Room Facilities


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HVAC systems in grow facilities do more than just maintain a comfortable temperature; they are crucial in creating the perfect environment for your plants to flourish.


They regulate temperature, humidity, and airflow, all of which have a direct influence on plant health and growth.


Let’s break it down:


Temperature Control

Cannabis plants thrive within a specific temperature range. Overheating can lead to wilting or stress, while low temperatures can hinder growth.


An efficient HVAC system ensures the optimal temperature range for your plants, fostering healthy growth and development.


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Having more control of temperature can help:


Prevent Disease: Many plant diseases thrive in extreme temperatures. By maintaining a consistent temperature, an HVAC system can help prevent the spread of these diseases.


Enhance Photosynthesis: The process of photosynthesis, which is how plants convert light into energy, is highly dependent on temperature. By controlling the temperature, an HVAC system can enhance the rate of photosynthesis, leading to healthier, more vigorous plants.


Improve Nutrient Uptake: The temperature of the growing environment can affect a plant’s ability to take up nutrients. Too cold, and nutrient uptake can slow down or stop entirely. Too hot, and the plant may take up too much water and not enough nutrients. Temperature control can ensure optimal nutrient uptake.


Control Transpiration: Transpiration, or the process by which water is lost from plants, is directly affected by temperature. By controlling temperature, an HVAC system can control the rate of transpiration, preventing both dehydration and waterlogging.


Energy Efficiency: Temperature control is one of the most energy-intensive aspects of running a grow facility. An efficient HVAC system can reduce energy consumption, leading to lower operating costs.


Additional Information:

  • The ideal temperature range for cannabis plants is typically between 70-85 degrees Fahrenheit during the vegetative stage, and 70-80 degrees Fahrenheit during the flowering stage.

  • Temperature control also helps in maintaining the quality of the buds, as extreme temperatures can affect the potency and flavor.


Humidity Control

Humidity impacts a cannabis crop in many of the same ways as temperature and has a an equally enormous impact on the plants' development.


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Having more control of humidity can help:


Prevent Mold and Mildew: Proper humidity control can help prevent the growth of mold and mildew, which thrive in high humidity environments and can damage or destroy cannabis crops.


Optimize Transpiration: By controlling humidity, an HVAC system can optimize the rate of transpiration, preventing both dehydration and waterlogging.


Enhance Nutrient Uptake: The rate of nutrient uptake in plants can be affected by humidity levels. Too high, and the plants may take up too much water and not enough nutrients. Too low, and the plants may not take up enough water, affecting nutrient transport.


Improve Plant Health: Plants can become stressed in conditions of low or high humidity, leading to stunted growth or increased susceptibility to disease. Maintaining the right humidity levels can improve overall plant health.


Regulate Stomatal Opening: Stomata are small openings on the leaves of plants that allow for gas exchange. The opening and closing of stomata are influenced by humidity levels. Proper humidity control ensures optimal stomatal function, promoting efficient photosynthesis.


Energy Efficiency: Humidity control is another one of the most energy-intensive aspects of running a grow facility. Strategically choosing the right HVACD system design can lower life-cycle cost.


relative humidity. optimum zone for humidity. chart of percent in relative humidity. relative humidity chart. engineered temperature solutions logo.

Additional Information:

  • The ideal relative humidity for cannabis plants is typically between 40-70% during the vegetative stage, and 40-50% during the flowering stage.

  • Proper humidity control can also prevent issues like bud rot and powdery mildew, which can severely affect the yield and quality of the crop.


Airflow Control

As with temperature and humidity, airflow also impacts many of the same aspects of cannabis plants, but in its own unique way.


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Having more control of airflow can help:


Prevent Mold and Mildew: Proper airflow can help prevent the growth of mold and mildew, which thrive in stagnant air and can damage or destroy cannabis crops.


Strengthen Plant Stems: Airflow can help strengthen plant stems. As the air moves around the plants, it causes slight movement in the plants, which can result in stronger, more robust stems.


Aid in Pollination: For plants that rely on wind for pollination, adequate airflow can help distribute pollen from male to female plants.


Regulate Temperature: Airflow helps to distribute heat evenly throughout the grow room, preventing hotspots that can damage plants and ensuring that all plants are at the optimal temperature for growth.


Improve Gas Exchange: Proper airflow ensures that there is always a fresh supply of CO2 for photosynthesis and helps to remove oxygen produced by the plants.


Reduce Pest Infestations: Many pests prefer environments with stagnant air. Good airflow can help deter these pests, reducing the likelihood of infestations.


Remove Water Vapor: According to the National Oceanic and Atmospheric Administration,


"Increased movement of the air around a plant results in a higher transpiration rate. If there is no wind, the air around the leaf is still and transpiration raises the humidity around each leaf. Wind moves this saturated air away from the leaf, replacing it with less saturated air."

 

Types of HVAC Systems for Grow Room Environments

When it comes to indoor grow environments, not all HVAC systems are created equal.


The type of system you choose can have a significant impact on your crop yield, product quality, and overall profitability.


Let’s take a closer look at the different types of HVAC systems commonly used in indoor grow environments:


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Decoupled HVACD systems

A Decoupled HVACD system, which stands for Heating, Ventilation, Air Conditioning, and Dehumidification, is a unique type of HVAC system. It distinguishes itself by independently managing the processes of heating, cooling, and dehumidifying.


This individual control, often referred to as decoupling, enables each process to operate autonomously. The result is a more precise control over the indoor environment, ensuring optimal conditions for growth and productivity.

  • Decoupled systems allow each component (heating, cooling, and dehumidification) to be controlled independently, providing greater flexibility and more precise control over the indoor environment.

  • May not be as energy-efficient or durable as purpose-built systems in an indoor agriculture setting.


Examples of Decoupled HVACD systems:


1. Standard Packaged Air-Handling Units with Direct Expansion (DX) Cooling: These are basic systems that work in conjunction with additional dehumidifiers (hung from the ceiling within the grow room).

2. Water-Cooled Heat Pumps: These setups have the ability to dispel heat into a geothermal loop or a fluid cooler. When using a heat pump, it is often necessary to combine them with additional dehumidifiers.

3. Ductless “Mini Split” Heat Pumps with Stand-Alone Dehumidification Equipment: These systems are compact and flexible, making them ideal for smaller grow rooms.

4. Variable Refrigerant Flow (VRF) Heat Pump Systems with Stand-Alone Dehumidification Equipment: These systems offer high efficiency and flexibility, allowing for individual temperature control in different zones within the grow facility.


Purpose-Built Integrated HVACD Systems

A purpose-built HVACD system integrates heating, cooling, ventilation, and dehumidification into an all-in-one solution that is specifically designed for the unique needs of the application (such as cannabis cultivation).


  • These systems are designed to work together, which can lead to greater efficiency and potentially lower energy costs.

  • Can be easier to maintain as there is only one unit.

  • May not offer as much flexibility as standalone systems as the components are not separate.


An Anderson Porter Design study (highlighted by Cannabis Science and Technology) evaluated three different types of HVACD cultivation systems (ductless mini splits, VRF split systems, and integrated HVACD).


It found that the decoupled (HVAC) system with independent cooling equipment and standalone dehumidification have the lowest initial cost but may not be the most energy-efficient and can have higher life-cycle costs than other HVACD options suitable for cannabis production, such as integrated ducted systems or hydronic HVACD systems.

Desert Aire, an HVACD system manufacturer, highlights that,


"The wasted energy is the direct result of the inherent limitations of the two separate systems to work in unison. Instead of efficiently removing moisture and heat simultaneously with one integrated system, two separate systems are toggling on and off trying to get the right mix of cooling and moisture removal. In this scenario the equipment will run longer than necessary due to the heat added by the standalone dehumidifiers as they work to remove the moisture. Once the moisture is removed, the AC units then need to turn on to remove the additional heat. Often times the AC will overshoot the temp set point and overcool the space which drives up the RH% causing the dehumidifier to turn on which adds more heat restarting the process."

From this we can see that even using two pieces of efficient stand-alone equipment doesn't mean that the process will be the most 'efficient' due to the lack of integration between the two systems.

 

Design Considerations for your Grow Room HVACD System


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When it comes to the design and specification of a comprehensive HVACD system for cannabis cultivation facilities, there are many other factors to consider, such as:

Controls: Controls for HVACD systems in indoor grow rooms are crucial. Ideally, HVACD equipment and sensors should be integrated with controls for grow lights and the fertigation system for ideal synchronization of the plant habitat.


Filtration: Involves using filters in the AHU to clean the air in the room and protect the equipment. MERV 13 filters are common, but some growers use even more efficient filters, including MERV 14, MERV 16, and HEPA (high efficiency particulate air).


Disinfection: UV lights, bipolar ionization, and photocatalytic oxidation are just a few of the methods available. These can be used in a central air-handling system or within the room itself. Between harvests, some growers will turn off the HVACD, put the lights to full power, and allow the room temperature to rise over 125 F to help control contaminants.


Odor Mitigation: The natural growth of cannabis plants and other processes emit terpenes, which are Volatile Organic Compounds (VOCs) known for their strong odors and why mitigation is usually required for an exhaust source on a cannabis facility. Carbon filters are commonly used to control odor, but there are other solutions available.


CO2 Enrichment: The process of constantly monitoring the levels of carbon dioxide in the grow room. If high levels are detected, purge ventilation (rapid removal of stale, moist air, and pollutants) is used to exhaust the excess gas.


Condensate: Grow rooms experience a high latent heat load, which results in a significant amount of condensate being produced by the cooling and dehumidifier coils. This water can be gathered, processed, and then repurposed as irrigation water, substantially decreasing the need for raw water used to operate the facility. Read more about this in an article titled 'Cannabis Grow Facility Design 101, Part 2: Water Usage' by PHCP PROS.


Humidification: Some grow rooms, especially those for younger and smaller plants (Veg rooms), may require added humidity. The HVACD system may over-dry the room when cooling the space, so humidification may be necessary.


To read more about Cannabis Grow Facility Design, visit the PHCP PROS website.

 

Incentives for Using Energy-Efficient Equipment in Your Grow Room


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Cannabis Business Times did a study on rebate acquisition and awareness revealing that of their 91 participants, 56% had not explored rebates or incentives. Of that 56% of participants, 24% were aware that there were rebates and incentives but hadn't explored them, and 32% were completely unaware.


This clearly shows that awareness is lacking, which is why we are highlighting this information, and encouraging those of you in the business to make this a priority.


Let's take a closer look at what is available:


Rebates

Rebates exist for multiple aspects of indoor cannabis grow facilities, from LED lighting to HVAC-D to CO2 systems. According to ProCanna, "Many cannabis operators can net cash incentives worth 50% or more of the cost of installing new energy-efficient grow equipment."


Cannabis Business Times lists tips and insights offered by Resource Innovation Institute (RII) to get the most out of these utility incentive programs, which includes:


Prescriptive Programs

Typically focus on energy-saving measures or technologies and offer predetermined incentive amounts. For instance, one program might provide a $250 discount for each high-efficiency LED lighting fixture that is purchased and installed.


Custom Programs

Geared towards more unique projects outside of the scope of the prescriptive programs and are particularly useful for those looking to utilize more efficient HVACD equipment.


They require a more detailed analysis of the proposed projects’ energy savings potential and typically involve more effort on behalf of the utility customer.


Some programs go so far as to offer incentives for (provable) general efficiency and resource-use improvements.


"Purpose-designed, integrated HVAC-D systems can save up to 40% in energy compared to standalone equipment,"

says Chip Seidel, Director of Indoor Agriculture at RII member Desert Aire.


These programs are sometimes housed within an energy supplier as part of a utility or, in other cases, are administered by third parties called implementers.


These incentives can significantly reduce the cost of installing energy-efficient systems like LED lighting and purpose-built integrated HVAC-D.


It’s important to note that the availability and specifics of these incentives can vary by region and utility provider.


It’s always a good idea to research local programs and consult with a professional to understand the best options for your specific situation.

 

Need Help Cutting Costs and Protecting Yields at Your Grow Facility?

We thought you would never ask! Engineered Temperature Solutions is here to help with all of your grow and cultivation HVACD needs. Contact us for a free site survey today so we can determine the specific requirements of your facility.


 

Conclusion

As we’ve seen, a well-maintained and optimized HVAC system can significantly improve operations and increase profit in grow facilities.


From disease prevention to environmental control, HVAC systems play a pivotal role in ensuring optimal plant health and product quality.


With the right strategies, HVAC systems can be optimized to increase crop yield and reduce energy costs by up to 40%, leading to increased profitability.


As a facility manager or business owner, the success of your marijuana crops and the profitability of your business are in your hands.


Optimizing your HVAC system could be the game-changer you’ve been looking for.


Remember, small changes can lead to big results.


If you have additional questions about your grow room, contact Engineered Temperature Solutions by clicking the banner below.


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If you enjoyed this article, stick around and check out others like it on the ETS blog page!


References

  1. Schimelpfenig, G, Megerson, J., Anderson, B., Zartarian, M., Integrated HVAC Systems for Cannabis Cultivation Have the Lowest Life Cycle Cost, Cannabis Science and Technology, 2023, 6(6), 16-21.

  2. Growers in Search of HVACD Efficiency, https://www.desert-aire.com/news/growers-search-hvacd-efficiency.

  3. Cultivation HVACD System Comparison Study, https://issuu.com/anderson-porter-design/docs/230120_cultivation_system_comparison_study.

  4. https://www.andersonporter.com.

  5. Eddy, Robert, Cannabis Business Times - 8 Tips to Maximize Cannabis Cultivation Energy Efficiency Rebates, 2024, https://www.cannabisbusinesstimes.com/news/maximize-cannabis-cultivation-energy-efficiency-rebates/, 05/22/2024

  6. G. Schimelpfenig and L. Morlino, Cannabis Science and Technology 5(1), 30-31 (2022).

  7. PHCP PROS, Cannabis Grow Facility Design 101, Part 3: HVACD and Air Distribution, (2022)

  8. Learning Lesson: Leaf it to Me, https://www.noaa.gov/jetstream/ll-leaf, 5/22/2024

  9. Emma, Vanstone, Investigating The Effect of Increasing Temperatures on Transpiration, https://www.science-sparks.com/investigating-the-effect-of-increasing-temperatures-on-transpiration/ , (2022)

 

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