This article is part of a series on how HVAC professionals can break into the cannabis industry. 

The construction of commercial cannabis grow houses can be a growing (pun intended) source of business for HVAC contractors and technicians. Grow houses require strict temperature controlled environments; the kind of environments HVAC contractors can provide. But before diving head first into this booming industry, experience and education are key to cultivating success for your company.

First, check to see how the current marijuana laws apply to your state to keep your HVAC business out of any potential legal hot water. Second, forget what you think you know about agriculture and growing plants indoors. Cannabis plants are far from your everyday houseplant, and treating them like so can be a costly mistake for you and your customer.  

Familiarize yourself with the HVAC units and systems that are needed to keep cannabis plants happy and healthy. For starters, commercial cannabis grow houses generally use fabric duct systems over traditional sheet metal ducts. 

"The cannabis industry loves cleanliness," explains Excel Air Systems, a designer and manufacturer of environmental control units specifically for sealed room applications in commercial grow houses. "This is because cannabis is a consumers product. We have made sure everything we do is food grade approved. By being able to throw our fabric ducts in the washing machine after every crop out ensures your room will always be able to achieve/set new standards for cleanliness in this industry."

Traditional galvanized ductwork requires access points for duct cleaning services. The more access points, the greater the risk of imbalance and unwanted contamination from bacteria or chemicals used during duct cleaning services.

"We have engineers that will build fabric ducts completely custom for almost every customer," says Excel Air. "One main reason is because every set up is different then another person's set up." And that is by far the most important tip. 

There is no one size fits all solution for installing HVAC systems in commercial grow houses. However, there are a few broad guidelines to remember when it comes to the pros and cons of fabric ducts over metal ducts in these environments, according Excel Air Systems.

Air flow in commercial grow houses is a delicate detail  

A fabric duct system enables air duct supply holes to be placed anywhere needed for optimal air flow. 

"Our engineers will base how many holes and what size the air distribution holes are based on static pressure of the unit, length of the duct, diameter for supply air, and of course the maximum CFM of the unit itself this will help guaranteed a nice even distribution all throughout the room while ensuring no hot and cold spots. We are able to do this, because the fabric duct itself, will inflate from the very end of the duct all the way to the front, this is how we know we have even air distribution." 

Excel Air Systems recommends air duct supply holes be placed at four and eight o' clock to be sure air doesn't pass straight out the side or straight down to the ground. "When we do it at four and eight o' clock, we notice it really helps with creating the air turns within the room. However depending on the set up, if you have a duct against one side wall we are only going to get holes on one side of the duct, that is because the holes are up against the wall. This will build unnecessary static pressure."

air flow diagram inside commercial cannabis grow room

Unsealed ducts require a sealed room for cannabis growth

Because fabric duct can't be insulated like metal duct, the entire room must be sealed for temperature control. Additionally, by being able to mathematically calculate the need for supply by the length, diameter, static pressure and the CFM of the duct, the exact size of each hole and how many holes for the supply air can be determined.   

"Traditional metal ductwork has been known for not only condensing when not insulated but when condensation happens, this opens up the potential of your duct getting rusty. Or, worse case scenario, drips of water on the plant itself. Our fabric ducts will not condensate or collect dust as we have a 2CFM positive pressure around the whole duct to help ensure this does not happen." 

No matter what fabric duct you are using they will all be super lightweight, machine washable, and my personal favourite they are flame retardant, so if your room were to catch on fire these ducts are meant to put themselves out!  super easy to install as most of the our air craft cable with your eye bolts and tensioners, however as I said some hardware changes on what type of duct we are using. 

Rigid metal ductwork may restrict much needed airflow in commercial grow houses

"Traditional Metal Ductwork is heavy, rigid and may restrict air flow to certain area's, this tends to create hot and cold spots or in some cases drafts." Fabric duct can be engineered with laser cut holes, this allows for precise placement of your air supply while being breathable and giving you flexibility. Then there is the obvious weight difference. 

"Fabric is much lighter and easier to install unlike traditional metal ducting, being heavy and attaching numerous sections together to achieve your desired length.Our fabric Ducts come as a kit with the duct work and the Hardware and can installed the second you take them out the box, this can be done almost effortlessly with less time then a regular Metal Ducting."

Fabric HVAC duct in commercial grow houses is versatile

In addition to being noise absorbent, fabric duct can easily be moved and reconfigured for a drying room. "The ducting will be a completely different design then any other rooms within the building. This is because when it comes to a dry room, we don't want to blast cold air on it. So we use a micro mesh fabric material that will essentially "mist/rain " the air, allowing it to properly dry not only the outside of the bud but be able to properly dry the inside without leaving the outside of your bud crunchy."

commercial cannabis dry room concept

As shown above, fabric duct allows for sections to be quickly added to design different HVAC system setups with a zipper and cap system. "It's just as simple as it sounds. Unzip your end cap, and zip on the new extension piece and you're done. We are able to do many shapes and colors and even add logos. There are a couple different fabrics you can choose from: one being flame retardant and the other antibacterial."

If you are an HVAC contractor looking to break into commercial grow housing projects, this all can be a lot to ... inhale at once. There is still the matter of choosing the right HVAC systems for the job and knowing how to correctly market your company's newly acquired "green thumb." 

But if the changing marijuana laws are any indication, this source of potential business is only going to keep growing.

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