HVAC - what’s your setup?

What do you use to control temperature and humidity? How much power is it occupying in your budget? How do you prevent microclimates?


This question can get deep when talking commercial facilities where there are a few different options to get where you need to be. My preference when talking smaller than 40-50k sqft is Water chillers w/fan coils and independent dehumidifiers for room specific control, next for that size is custom units to cool/dehumid/and/or re-heat, vs big dog systems (50k sqft and up) with Water Cooling and stand alone dehumid… When building large scale facilities your cooling system, and included with that (but not as costly) your dehumidification system, are going to be one of, if not your biggest expense (in terms of setup cost as well as power) outside of the building itself.

We avoid microclimates by having insane air movement, lol, and airflow from all directions, not just wall mounted fans. The vertical air movement throughout the canopy area is crucial to that as well as fans on the ground moving air under the canopy and grow tables.

Now for the caregiver growers and home growers out there using a mini-split system is the way to go and they’re pretty easy to install, even ones that don’t just plug and play. For most installs all you need for parts are as follows: standard Allen wrenches screw drivers and such, ex-large, large, and medium size crescent wrenches, Mini Split System Low Side Charging Manifold w/Pressure Gauge Hose Set, something some of you may already have… a 3 CFM or better vacuum pump, 110V or 220V breaker for power box (depending on size and Voltage of your unit), a hole saw set 1" thru 3", and some wiring know-how. If the area you’re using has your home AC ducts running to it thats fine just make sure to add a backdraft dampener the end of your AC vent/duct entering the grow room to avoid issues, and just have it set to comfortable temp all day and night ~75’ give or take. Let the mini-split do the real specific room temps for you (units with heating options are clutch for this). A mini-split will dehumidify whenever it runs, and when ran with a room exhaust system you should control most your humidity, but depending on your room size, plant count, and size of your plants you may need additional stand-alone dehumidifiers. Hope this helps… pardon typos, lol.

Endo Farms.


Dropping knowledge. My man!


Off the shelf air conditioning equipment is the most popular method for dehumidification and cooling a cultivation environment but also the least efficient.

Dehumidification and cooling cannot be served effectively with a single unit that cools to dehumidify, while simultaneously heats to avoid over-cooling. Serving the needs of both functions effectively and efficiently, requires a “decoupling” strategy.

    Separating cooling and dehumidification results in optimal control over temperature and humidity.

Learn more at CannabisClimateSolutions.com


Bumping this topic for the new folks. What do you use for your HVAC setup?

For large grows, our strategy is to use wrap-around-plate dehumidification for the dehumidification load. Cooling and heating coils are added to the common airstream to control temperature. A central chiller with glycol charge is used to deliver 32f water to each dehumidifier and cooling coil. Heating is usually hot water but could also be electric.

We urge the grower to use the VPD chart to determine operating conditions.


Where do we start? So many options!

To the point of Endo Farms and even msptechnology there are many different solutions out there. To keep things fairly brief here are a few rules of thumb when designing your space.

  • Physical space size isn’t as important as calculating your actual load (Yes, even LED’s emit heat, hehe). Take your total watts of lighting and multiply it by 4 BTU’s. (12,000 watts x 4 BTU= 48,000 BTU / 12,000 BTU per ton= 4 Ton A/C system). This calculation is based on an 80F outdoor day with R12 insulation in your room. This also takes into account ballast in the room and burning Co2. You should be able to maintain 76-78F room.

  • A ducted system is the way to go. Why is this? There are many reasons such as even distributing the air throughout your room as to not have any hot or cold spots. This will also help in mixing the rooms air to help with Co2 infusion, UV air purification for spores, bacteria and mildew along with ensuring consistent dehumidification throughout the space. Also, to reduce overall power consumption and upfront cost you will be able to split the system cooling 12 hours to Room A and the other 12 hours to Room B using automated dampers which can be extremely beneficial for startup growers.

  • Minimize the complexity of what you’re trying to do especially for those in large facilities where scaling and efficiencies are extremely important. Try to have smaller grow rooms vs. massive sea of green (30-50 light spaces) this will ensure you dial in that room, any issues won’t affect the entire operation and one or two people can easily maintain each space. Stay away from one large system in the space as if anything were to happen you want redundancy and not complete crop loss. Lastly, choose an environmental system that can provide the greatest level of control but is designed for anyone to use. The easier the system is to run, the more comfortable the people onsite will be maintaining it.

Obviously, there are many other rules of thumb and I would be more than willing to continue the conversation so just let me know! Cheers!

Brandon Kion
Excel Air Systems


Hmmmm… I see a lot of talking about the fact that you disturbe microclimates and I see lots of wall fans.

I am of a different school. A microclimate around the leafs is natural. You should not disturb that or you will get what we call “fan burn” (yellowing of particularly the top 3-6 inches of the crop. When disturbing the relatively humid microclimate around the leaf with lots of aggressive air movement, the plant will eventually just close the somata and tell you to f*** yourself ( excuse my French :slight_smile:) because it can’t keep up with the transpiration - it will stop cooling itself.

Walk around in a huge greenhouse and see how many fans are there for cooling and watch the the air movement.

I agree that distributing the air throughout the room is the best solution. Top to bottom to mix the warm air with the dropping cool air. However, in contrast to excelair I do believe in large rooms. Foremost from a lighting and overhead of paths point of view. It’s more efficient, specifically with rolling benches. I understand the challenges for HVAC but I am just looking at the process and the bottom line. Also, large rooms are much slower and more stable in climate than small rooms.