Take control of your grow operation! Maintaining proper temperature and humidity is a complex, but vital process when designing a grow facility
An artificial environment is something all indoor growers must create, and this applies to greenhouse growing as well. Even those growing outdoors have some ability to manipulate the environment immediately surrounding their plants and farm.
These differing conditions are commonly referred to as micro-climates, and they naturally occur everywhere. A good micro-climate analogy is comparing the northern and southern slopes of a mountain. The same mountain can have different ecological systems because of direct sunlight, and it’s a good example that demonstrates the many different variables that can influence the climate. In this case, it was the shade created by the mountain itself that caused the different climate.
Cannabis adapts to almost any climate, especially through breeding programs. The plant’s reaction to the ever-changing outdoor climate is responsible for bringing out subtleties in cannabinoid and terpene profiles that can’t be duplicated in artificial environments (AE). Indoor growing has an upside though, and that’s the ability to duplicate consistent environmental conditions. This ability to create optimal conditions must be taken advantage of for indoor-grown plants to reach full potential.
Technology has caused a storm of excitement when it pertains to controlled atmospheric growing environments (CAGE). The ability to dial in your CAGE, even compared to 10 years ago, means your grow room can sustain environmental conditions anywhere between Northern California and Thailand.
Although all CAGE will use the same equipment to maintain control, when designing your grow room, the process begins by learning what your plant’s environmental set-point is. This is important because if your focus is on growing sativas, like a Thai varietal that has adapted to humid, sweltering conditions, then maintaining 65 degrees and 30% humidity will not make the plants happy.
So when you’re in the design phase of your operation, kick-start the whole HVAC conversation by first determining what environmental conditions need to be achieved. Deciding on the number of varietals to grow makes this process more straight forward. One option more growers are taking is designing individual flowering rooms or whole greenhouses dedicated to one strain or one environmental set-point. Doing this reduces the complications of making multiple varietals happy in one space. It also reduces the resources needed to condition different areas of one grow facility. This philosophy will apply particularly to the drying and curing areas, but also to the cloning chamber, vegetative and flowering rooms. All these individual environments will require different mechanical inputs to achieve the desired results.
Now that we understand the importance of creating an AE, let’s look at the considerations for controlling the environment. To begin, growers need a properly constructed facility to handle the rigorous demands of an enclosed growing environment. Greenhouses get two green thumbs up because of their inert construction materials. Metal building materials can better tolerate the corrosive nature of an enclosed growing environment. The bottom line is that you cannot over-build when it comes to withstanding an indoor growing environment.
When constructing an indoor facility, build the bones out of metal, or at least consider framing the exterior walls of your growing facility out of metal studs. The shell of your building is the next item for consideration, and metal siding is a great choice here. With modern building techniques and materials, the building’s envelope needs to be built to create a thermal break. A thermal break means your insulated walls don’t allow temperatures to transfer back and forth. When temperatures pass back and forth between walls, there is a higher probability that moisture will form within the wall cavity, especially when accompanied by higher humidity. If you construct your facility with wood walls and don’t create a thermal break, it’ll be just a matter of time before mold begins to form.
The interior of your grow room walls should be tackled next. The material you choose, and how you apply it, is very important. Sheetrock will work, but make sure you seal it with a water- and mold-resistant material. Even if you plan to cover the wall with a reflective material, it needs to be sealed underneath. A good material to use on interior walls is ThermoMax — an insulated, waterproof finishing panel that resists mold and carries a fireproof rating. That’s a made-to-order CAGE building material if there ever was one!
– Temperature: Of all the parameters, temperature is far and away the most critical variable to control in your garden. Heat has devastating consequences on cannabis, especially during florescence. When it gets too hot and dry, the stoma will close in order to preserve water and transpiration slows to a halt.
This can become hyper-critical if you employ any techniques that override your plant’s normal stomata response factors. Trichome production is another area that suffers from too much heat. This can be caused by direct heat, such as the lamps being too close, or overall ambient temperatures being too high.
The considerations for controlling heat begin with the type of grow room you’re designing. The majority of grow rooms rely on a transfer of fresh air. Old air is exhausted as fresh air is brought in to replace it. These systems are generally controlled by a thermostat. It’s a simple, cost-effective method for controlling heat.
Meanwhile, closed-loop systems call for zero air exchange. These systems are more complex and finicky to operate, and really could fall into the category of being clean rooms. There are two common approaches to handling the issue of heat load, whether you’re directly exchanging air out of the room or not. The decision that has to be made from a design standpoint is whether to remove the heat from the source (light bulbs), or concentrate on removing the heat from the room.
– Humidity: Water is responsible for sustaining life. However, water can wreak havoc in an enclosed space if you haven’t designed your facility and HVAC correctly. Organic building materials coupled with too much humidity can lead to destructive mold in several seasons. To pile insult on top of injury, while the facility is breaking down, there’s a good chance that molds and mildews have also infiltrated your crop. It’s the big double whammy!
The irony of humidity is that those same conditions that will ruin your structure and make pathogens feel at home are the same conditions that plants thrive in. This conundrum is dealt with head-on by building a properly constructed facility, and then equipping it to manage the environment correctly. No indoor grow room should be without dehumidification, and it’s truly the only possible way to maintain the proper ambient humidity.
These systems are rated by pints of water removed from the atmosphere per hour. Bigger is definitely better when it comes to dehumidifiers. The catch is that their ability to remove water is tied to temperature, which is usually around 85 degrees. So a machine that’ll remove 150 pints of water a day at 85 degrees begins to lose its water-removing capacity as the temperature drops. Commercial systems are made to operate in slightly cooler temperatures, so consider your room’s operating temperature when figuring out which system best suits your needs.
– Air quality: Indoor growing facilities need to be treated like clean rooms, especially in relation to air quality, so the air inside the growing room will have to be conditioned. Conditioning air means manipulating the temperature, humidity, CO2 levels and cleanliness. The biggest difference concerning fresh-air systems and closed-loop systems is the CO2. In closed-loop systems the ambient CO2 level will have to be maintained; with fresh-air systems, it’s handled naturally, and t’s very important for the incoming air to be filtered really well.
These air intake systems can be designed and installed by licensed HVAC installers; however, if you’re inclined to build these filtering systems yourself, here are some tips: Have the metal filtration boxes made by a professional — they will need a drawing with dimensions to do this. The filter box will need to be designed with installation parameters and filtration needs in mind. With filters, you’ll need to size them properly to handle the air flow. Filters are designed by the area of their medium, so choose pleated filters, which allow for more air flow per square inch. High-efficiency particulate air (HEPA) filters are preferable, and capture 99.97% of all air particulates.
The most overlooked aspect of indoor air quality is the use of sterilization systems and recirculating filtration boxes. Once the air enters the grow room, it should be continuously scrubbed and sterilized in either fresh-air or closed-loop systems. There are great products on the market to handle these scenarios, so do some research, and figure out what will work best for your situation.
This is a very broad subject, but lighting is an integral part of the environment in its relation to heat. Lighting is responsible for at least 80% of the heat load created in a grow room. This figure drops if you choose LEDs over high-intensity discharge lamps.
Another method for removing heat from the source is by using ventilated hoods. Most vented hoods use in-line fans to evacuate heat from the room. Some use water-cooled jackets, either alone or in conjunction with vented hoods. These water-cooled venting systems attach to the exit end of a vented hood and recirculate water back and forth from your mini-split heating and cooling system. This removes a big percentage of heat and reduces the direct AC requirements.
Targeted Environmental Control
Prior to legalization, cannabis production was truly a low-tech endeavor. Cannabis growers didn’t have access to HVAC professionals and other mechanical contractors pre-legalization, so most HVAC needs have been handled via fresh-air intake venting and focused on whole-room air conditioning. With this new access comes the ability and resources to design and build proper growing facilities.
A concept that’s used in other industries, and only recently being focused on cannabis production, is targeted environmental control (TEC). The idea is to concentrate heating and cooling right where you need them, as opposed to controlling an entire room. This saves tremendous resources while providing a superior environment for the plants — that’s a win-win all the way around.
Quality over Quantity
This age-old philosophy should definitely apply to cannabis stewards in every aspect of their operation. If your goal is to grow truly great cannabis, then creating an ideal environment is top priority. Unfortunately, in the quest for yield, budgets are often consumed by building out larger cultivation areas and limiting the resources to properly equip them. Doing so will always lead to a lower quality product. In the end, always build out to your means, and grow to where you want to be.
Until next time, remember, “Stay focused, and let it grow.”
Chris Bayley is a cannabis enthusiast and production specialist. He operates Hortistructure, Inc. and Elemental Gardener out of Tonasket, Washington. He can be reached at firstname.lastname@example.org.