Things You Need to Know About Industrial Dehumidification for CEA

Proper dehumidification is essential to create the ideal environment for plants to grow. Without adequate dehumidification, the air inside a greenhouse or indoor farm can become too moist, leading to problems like mold and mildew growth.
April 30, 2022

Most people think of agriculture as an outdoor activity, but in recent years, there has been a growing trend (pun intended) of cultivating on a commercial scale indoors. Indoor horticultural operations offer a number of advantages over traditional farming methods, including year-round production, protection from pests and weather, and reduced water usage. However, indoor agriculture also comes with some unique challenges, one of the most important being the need for proper dehumidification.

Dehumidification is the process of removing water vapor from the air. In controlled environment agriculture (CEA), dehumidification is used to create and maintain optimal conditions for plants. By reducing the amount of moisture in the air, dehumidifiers help to reduce humidity levels, which encourages proper transpiration and nutrient uptake and helps to prevent mold growth. Dehumidifiers can also help to lower the risk of pests and diseases, as they create an environment that is less conducive to their growth.

However, simply running a dehumidifier is not enough to ensure proper humidity control. Dehumidifiers must be adequately sized for the space, and they must be positioned effectively in order to maximize their efficiency. The entire HVACD system must be designed with dehumidification top of mind, so your mechanical designer should have a deep understanding of your irrigation methods, volume, and desired parameters to design the appropriate amount of dehumidification into the system.

By following these best practices, agricultural facilities can maintain the ideal humidity level for their crops, protecting them from both mold and dehydration.

The Need for Dehumidification in Indoor Agriculture

In any agricultural setting, whether it be a greenhouse or an indoor farm, humidity levels must be carefully monitored and controlled. High humidity levels can create an ideal environment for mold and other pests, while low humidity levels can cause excessive transpiration and poor yields. As a result, agricultural facilities must take steps to maintain appropriate humidity levels through the use of dehumidifiers, or an integrated HVACD system that includes humidity control.

Transpiration and VPD

First, you should understand the transpiration process and why Vapor Pressure Deficit (VPD) matters. Transpiration describes the way plants remove the water they don’t use. You might think of it as the plant sweating out its excess water. When the air is dry, the transpired water is easily absorbed into the atmosphere. If there is too much moisture in the air, however, your plants won’t be able to transpire. This is because the water vapor in the air creates pressure against the plants as they try to release excess water. VPD measures the relationship between temperature and humidity and how they will impact your plants. Without the ability to remove excess water, it becomes trapped, causing the plant to rot.

If you are growing plants in an enclosed space with warm temperatures, constant watering, and rows of plants transpiring, humidity levels can quickly skyrocket. As a result, dehumidification is an essential part of indoor agriculture. In addition to controlling humidity levels, dehumidifiers also have several other benefits for indoor agriculture.

Mold Prevention

Mold is one of the biggest problems when it comes to agricultural crops grown indoors. It thrives in humid environments and can cause serious crop damage, ruining an entire harvest if left untreated. Using dehumidifiers to reduce RH and maintain consistent indoor humidity levels can play a major role in preventing mold growth.

Factors to Consider When Choosing a Dehumidifier for an Indoor Grow Operation

When you’re growing indoors, you need to create a controlled environment that mimics the conditions outside. One important factor is humidity. When you choose a dehumidifier for an indoor grows operation, there are several factors to consider:

The Size of the Grow Space

The size of your grow room is a major factor in determining which dehumidifier you should buy. The capacity of a dehumidifier is measured in pints per day (PPD), and that number reflects the amount of moisture a unit can remove at 80 degrees Fahrenheit with 60 percent humidity. The actual output of the dehumidifier will decrease at lower temperatures and lower humidities and will increase at higher temperatures and higher humidities.

In order to calculate the actual load, irrigation volume is the primary driver. Assume that every gallon of water you irrigate will ultimately need to be removed through the dehumidification system, and take into account the performance curves on the dehumidification equipment to determine how much it will actually remove. Better yet, work with a reputable dehumidifier supplier and your mechanical engineer to ensure your equipment is properly sized.

Also, consider how often your dehumidification units will run. Most dehumidifiers can be integrated into your grow room controls and automation platform so that they work as a cohesive part of your HVACD system, turning on and off automatically as needed. For larger spaces, we love the Surna by Anden Grow-Optimized 710 PPD Dehumidifier because it uses Variable-Speed, Low Grain Refrigerant Technology (VLGR patent pending) to modulate the speed of dehumidification based on the precise load conditions of your grow environment.

The Target Climate and Humidity Levels in the Grow Space

The target climate and humidity levels in the grow space should be similar to their natural habitat. It is a good idea to research the native environment of your plant species to know the climatic conditions they prefer.

For example, cannabis tends to grow best in regions closer to the equator that is warm and humid. Its ideal climate setpoints vary depending on plant maturity and light source. Typically, cannabis cultivators will set their temperature between 76-84 degrees Fahrenheit when lights are on, and between 68-74 degrees Fahrenheit when lights are off. 50-60% RH is also typical, except in veg where the plants favor slightly higher humidity. However, leafy greens will typically thrive at a slightly cooler temperature and can tolerate slightly higher humidity.

The Price, Quality, and Efficiency of the Dehumidifier

An important factor that affects the price of a dehumidifier is its capacity. A unit with a higher capacity will probably require a higher initial capital investment.

However, if you try to save money by buying a small unit and then run it more often, you may not actually save any money at all. The extra wear and tear will likely cause the machine to break down much sooner than it was designed for, and you might need to purchase yet another unit to replace it. Not to mention running a smaller capacity unit longer could have higher energy costs in the long run.

Another factor is quality and performance. Check out buyer reviews and understand the specs of the units you are comparing. Only buy units that are UL or ETL listed and performance tested by a third party. 

Every grower’s needs are different, so there is no one perfect dehumidifier for everyone. The best option for you will depend on what you need to be an effective grower. Still, with the information provided here, you should be able to find the right dehumidifier that meets your needs and provides the right balance of performance and value. You should also work with your mechanical designer to ensure your system is properly sized and outfitted.

Desiccant vs. Condensing Units

There are two primary types of standalone dehumidifiers. Both types serve the purpose of removing moisture from the air. However, they use different technologies to accomplish this.

Desiccant Dehumidifiers

Desiccant dehumidifiers, unlike other types of dehumidifiers, do not need a compressor to remove excess moisture from the air. These units use absorption or adsorption into a media (usually silica or alumina pellets) that collect water vapor from inside the space. The desiccant media is then heated and the moisture is rejected outside the space.

In general, desiccant units are more expensive than condensing style dehumidifiers, but they are more energy-efficient in most cases. They can also reduce the humidity to significantly lower setpoints than condensing style dehumidifiers because there is no “floor” or point at which they can no longer operate. Condensing style dehumidifiers reduce the temperature of the air to below dewpoint in order to cause water vapor to condense into liquid where it is drained away.

However, if a cultivator wanted to reach extremely cool and dry conditions for whatever reason, the condensing style unit may not work, and in that case, desiccant would be the logical option. Extremely large cultivation facilities may also rely on desiccant technology to decrease energy consumption.

Condensing Dehumidifiers

To remove airborne water vapor, these units first draw in moist air from the grow room. As soon as the air passes through the cooling coils, it is cooled down to below the dewpoint temperature in the space, which causes water vapor present in it to condense and form water droplets. The air that has been now freed of moisture is then circulated back into the grow room. The moisture collected by this machine is then passed through a pipe into a drain or reclamation tank.

The dewpoint temperature is the temperature at which water vapor condenses into liquid water. The dewpoint temperature is a product of the temperature and relative humidity in the space, and changes with temperature or RH changes. Most condensing dehumidifiers are rated at 80 degrees F and 60% RH, which is a dewpoint temperature of 64 degrees. As the dewpoint temperature decreases, dehumidifier performance decreases, and as the dewpoint temperature increases, so does the dehumidifier performance.

It is important to remember that the dehumidifier needs to be placed in the right location so that it can be effective. A poorly installed dehumidifier will not perform correctly for any number of reasons, including airflow, access to moisture in the space, rejection of dry air where it’s useful, and may even be damaged by improper installation.

If you want to get the most out of your dehumidifier, hire a professional to help determine where it should be located in the space. Professional companies have experienced technicians who are trained to install a dehumidifier properly, and they can work with the mechanical engineer or general contractor to ensure the system is well coordinated.

Tips for Maintaining Optimal Humidity Levels in an Indoor Farm

Here are some tips for maintaining the right humidity levels in an indoor farm.

  • Ensure homogenous airflow in the space to the extent possible. CFD analysis can help you to get very precise with this, or you can install circulation and destratification fans where you identify hot or dead spots
  • Carefully monitor relative humidity. Sensors and control systems like SentryIQ can automatically track this data for you, and even initiate equipment to make adjustments if needed
  • Maintain consistent watering schedules to help avoid humidity spikes
  • Understand that changes in irrigation volume will have a direct impact on the humidity in the space
  • Understand that reductions in temperature or humidity setpoints will have a direct impact on the output of your dehumidification equipment
  • Use a humidifier to add moisture if necessary
  • Clean and maintain your dehumidifiers regularly to ensure optimal performance and to maximize your unit’s lifespan

Maintaining the right humidity level can be tricky in an indoor farm environment, but there are plenty of ways to ensure that your garden is operating optimally. The right environmental conditions can make all the difference between a flourishing garden and one that struggles to survive. Follow these rules for creating optimal indoor humidity levels and watch your plants flourish!

Addressing Mold and Powdery Mildew on Plants

Mold and powdery mildew on plants are caused by spores in the air landing on plants and growing. Mold can be many different colors, including white, gray, black, brown, or green. Mold and mildew can damage plants and can be dangerous if consumed. Once they are present in a crop, they are incredibly difficult to eradicate, and often result in the loss of an entire harvest.

Mildew and mold flourish in excessively humid environments, or in environments with unstable humidity. To prevent them from showing up in your garden, keep your humidity levels from spiking, practice routine hygiene practices, make sure your plants have enough room between them so that air can circulate freely, and quarantine outside plants before introducing them. Keeping leaves dry when watering will also help to prevent mold and mildew from growing.

What Are Mold and Powdery Mildew?

Powdery mildew can be identified by its appearance. It will look like white spots on leaves or stems and will have a dusty or cobwebby appearance. If you wipe the white substance off with your finger, it will leave an outline of the spot. Powdery mildew flourishes in high humidity areas like greenhouses. Since it is an air-borne fungus, it can travel from one plant to another quickly. If left untreated, the fungus will eventually spread throughout your grow, affecting your entire crop.

Mold appears in warm areas with poor ventilation and high humidity levels. It can appear anywhere on a plant as a fuzzy growth that is usually white, black, or green in color. Mold can cause serious health problems if inhaled or consumed, so it is important to take measures to prevent it.

Powdery Mildew and Mold Prevention Tips

Powdery mildew and mold are two words indoor farmers hate to hear. And while there isn’t a cure, there are definitely ways to prevent powdery mildew and mold from ruining your plants.

  • Prune: Prune out any diseased leaves or stems as soon as you see them. Destroy them so they cannot spread the disease further.
  • Avoid Overcrowding: Good air circulation is critical for preventing powdery mildew, so do not overcrowd your plants.
  • Check for Spores: Inspect your plants regularly for powdery mildew spores. These can be white, gray, or black and will look like a powdery substance on the leaves or stems. If you see any spores, take immediate action to prevent the disease from spreading.
  • Monitor Humidity Levels: Powdery mildew thrives in humid conditions, so try to keep the humidity levels in your grow room in balance and prevent spikes in RH. Work with your mechanical engineer to properly account for moisture removal and cooling loads.

Get Expert Dehumidification Solutions

Industrial dehumidification is necessary for maintaining a healthy indoor commercial farm. Contact us today if you are in need of a mechanical engineer and HVACD equipment supplier specializing in CEA.

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