Let's talk HVAC!

As I await delivery on a new split AC system, I wonder how other growers are mitigating heat issues in their cultivation spaces… For the last few years I have been building efficient lung rooms that handle air conditioning, humidification/dehumidification, and, to a slight degree, some CO2 saturation.

I love mini-splits. Over the last decade of growing, they have become my preferred means of coling grow rooms with efficacy and efficiency. I just ordered my first Mr. Cool split and I’m ordering another split this week. I have used many brands and have heard a lot of stories (good and bad) about peoples’ experiences with different AC brands. What have you found? What’s your favorite brand of AC? Any horror stories? Should I order this next split unit or should I maybe explore other options?

Give me a hand here, GNET!



Great topic Nick! Several years ago I tried out a few Gree mini splits due to the low cost and high SEER value. And while the units worked great the one glaring issue was that the air handler had to have visual contact with the AC remote. This proved a bit of a struggle, with all the EMF generated by the lighting in the grow rooms. We tried the wired thermostat, but those actually worked horribly, causing on a few occasions the cooling to shut off. The final solution was to hang the remote a few feet away from the air handler–the holder made of metal to block EMF from the lights. Lots of hair pulling, until then.


Wow! Thanks Ruben! I never even considered a line of sight thermostat as an issue; but then again I’ve never worked with a split unit that required line of sight to function! It’s cool you were able to Macgyver a solution that worked for you, but what a hassle! Great insight!

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I bought a mini-split for my house that gets full sun all day. It use to be unbearable in my house in the summer. Now I can get the house cooled to the upper 60s no matter how hot it is outside. Super cheap too. I think I spent $1600 (pre-charged) on a 2 ton unit for the main living area. I installed it myself and paid HVAC $400 to hook up the lines and release the refrigerant. Best dang thing since sliced bread! The brand I have is Ductlessaire, not a major brand, but it was cheap and has been working better than expected.


Yesssss! I love split systems! We did the same thing in the guest house: 400 square feet, cooled to perfection with a 1 ton LG mini split. Even on a hot (I mean HOT =: 117°F) summer day, I can bring the house down to the mid 60’s. When I remodeled the house, I did SUPER insulate it, though. Great insulation makes a big difference!


Only used mini-splits while living in the Caribbean. With 3X energy costs in Puerto Rico, it’s just more cost effective not to cool an entire home with central AC like many US homes.

Portable and window units can also be more efficient than central AC by allowing for temperature zoning. But portable ACs take up valuable floor space and window units may expose a security vulnerability or limit your placement options.

These devices are usually kicked on when temperature thresholds are crossed. Many use PID control.
Neither approach is perfect, the temperature can fluctuate and performance can depend on calibration.


Efficient temperature control should be adaptive to the conditions of your grow space, local weather patterns, and even consider things like whether you are running an exhaust fan or other appliances. Environmental control should be integrated so that we don’t waste energy exhausting cooling air or CO2.

What we’ve described requires a computer to monitor this information. To our knowledge, a device like Nest is the closest available product to the control we’ve described.

Kindbot currently uses PID to lock in on a set point, controlling a dumb AC with smart plugs but we are building an adaptive controller so that Kindbot will learn the most efficient control policy for your grow space.

This will mean somewhat better performance, lower energy costs, and more flexibility in AC selection since Kindbot will do the thinking for any AC by integrating more environmental info.

And since Kindbot is a computer, we can remotely access our devices using the mobile application without the line of sight issues in using IR remote controls.


We currently have 10- 3 ton Daiken mini splits in veg and flower rooms. Through trial and error and the ever evolving knowledge in this industry, we have come to the conclusion that mini splits are not a good option for cannabis cultivation on a commercial scale. Though they have high SEER ratings, they do a terrible job of removing humidity and offer no filtration. What helps to make them efficient, (many small thin coils) also makes them bad for grows. While this is great for human living space, it increases your dehumidification load. I see the bigger problem with them being that they provide many small places/surfaces for problems to hide. (mold pathogens, PM, pollen) I believe moving forward, the industry is going to move to more specialty HVAC solutions like Desert Aire systems that are more easily adaptable to indoor cultivation along with HVAC controls that can simultaneously control RH% and temp during lights on/off periods to a much lower variance. Another point to make is that your outside environment makes a big difference in your needs indoor. HIgh heat/low humidity areas need a lot of cooling, lower heat/higher humidity areas need as much dehuey tonnage as cooling tonage.


I love what you guys do at Kindbot! Thanks for all the info! I love how your controls flawlessly integrate with existing hardware!


I agree that for larger spaces split units are just not the way to go. I like them for smaller cultivation rooms (less than 1000 sq ft). I prefer many small spaces, even in a large commercial format because I can monoculture and thus fine tune all the needs of a given cultivar, stagger harvests to reduce overall workload and increase efficiency, and reduce strain on the drying room (I find I get better cure this way as well).

It’s exciting to see HVAC manufacturers getting into the cannabis space by making AC units tailor-made for our industry and needs.

You touched on another really salient point about split AC’s: if they are not regularly maintained and cleaned, they can be vectors for molds/mildews/gross stuff! Definitely something to consider when making HVAC purchases.

Thanks @shane1!


Thanks for taking one for the team! I am sorry your mini-splits are not working as intended for your commercial grow.


Live and learn right! Life would be boring if I didn’t get learn something everyday!


And we all learned something too!


If we’re all learning then this thread will serve it’s intended purpose. Thanks for making it a lively one!


Kindbot temp control now using AI instead of PID
temperature set point of 77 over 6 hours


All air conditioners make relatively poor dehumidifiers, as they move the air through the handlers too rapidly for effective dehumidification. Dehumidifiers perform best at a higher install height than most AC evaporators too, to pick up warmer and more humid air.

For larger grows the dessicant gas-fired units are far more efficient than compressor driven units, and can be mounted outside and ducted inside. It’s the next size down where it gets harder to find moderately-priced solutions.

You can always rent a solution and see how it works for you too, this place will deliver too:



Hi Guys! Kind of late to this party as I only recently joined the forum but I’ve had a great time reading all the posts (lots of quality information and debate here, which I really appreciate). HVAC in cultivation facilities happens to be a subject about which I’m pretty well educated so I thought I’d chime in on this one instead of just thread-stalking like I’ve been doing everywhere else.

I love how educated this forum is and you guys are absolutely right–mini-splits are a great option for comfort spaces and very small cultivation spaces, especially when there are budget limitations. But the SEER rating can be deceptive, because a) as you guys mentioned, they’re terrible dehumidifiers, and dehumidification isn’t considered in the efficiency rating, and b) in many cases that high rating is based on the use of an inverter for the system to be able to run at partial load, when your load in most cultivation spaces is constant (or very close to constant). This means that you don’t end up getting to capitalize on that energy rating in most cultivation environments–meaning that their real benefit is that they’re cheap and easy for small applications.

When you migrate to larger scale commercial applications, chilled water systems with heat recovery/reheat for dehu and/or packaged units with hot gas reheat for dehu are a substantially more energy efficient option, with the flexibility you need for dehumidification and maintaining tighter tolerances. Chilled water will typically get you better redundancy and lower connected loads on electrical as you can install fewer, larger chillers to supply cooling and dehumidification to an unlimited number of rooms without mixing air between rooms, and you have more air handling options with chilled water (ducted, ductless, custom, etc). To your point about multiple small rooms, Nick, chilled water would allow you to run a large compressor bank and fill your small rooms with ductless fan coils in whatever size is needed, so you can still independently control temp and humidity in small spaces but with a lower electrical infrastructure (especially if you’re operating on a flip) than with a bunch of 3 and 5 ton compressors. The HGRH units will typically have some integrated controls, and in either case, a good controls system is an absolute must.

Desiccant, as you guys mentioned, is probably the single most energy efficient means of stand alone dehumidification when properly deployed (it can also get you down to superlow humidity and can dehumidify at low temps for those of you who like very cold, very dry drying rooms), but it’s expensive and if you’re using a cooling system you’re getting dehumidification as a byproduct anyway so you won’t always need it as your first line of defense. With the right cooling system, the need for external dehumidification can be minimized or eliminated altogether.

I’m really happy to see you guys talking about maintenance and cleaning of the system, as people really don’t pay enough attention to taking care of the mechanical systems in their facilities in general. The mechanical (HVAC) in cultivation facilities is SO important, both because of temp and humidity but also exposure to fungus and pathogens. That starts with design of course, but proper cleaning and maintenance will a) make sure the system performs to the best of its ability (for decades if it’s the right design) and b) reduce your exposure to contaminants that can cause failed crops.


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