Regulating Humidity in a Cannabis Grow Facility

Professor DeBacco

Humidity is the measure of water vapor in the air.
Many growers think this is unavoidable and while this is true to an extent, if humidity goes unregulated the plants could…
Be more likely to get powdery mildew or bud rot if levels are too high
Suffer from leaf burn/water stress if the levels are to low.

To Control Humidity You Need to Control the Environment
To gain better control over the growing environment growers need to isolate their room.
But air circulation is still important.
Sealing off and insulating the growing area is one way to get isolation from the outside environment.
This is important regardless of the outside conditions

Temperature Regulation Impacts Humidity
Temperature regulation is important for the plants in general, but how this is accomplished can impact the humidity levels.
For Air Conditioning units make sure the unit is sized appropriately to reduce the chance of large temperature swings from a unit that is either to large or small for the area.
The goal is to have your until run for consistent cycles for longer durations to moderate temperature changes.
Avoid short on and off cycles which will reduce the life expectancy of the unit and not be as beneficial for the plants.
Temperature and Humidity
Temperature and Humidity are inversely proportional.
When the temp. goes down… Humidity goes up
This is why swings in temperature impact humidity as well which will relate to potential disease pressure.
Goal is consistency.

Importance of Air Circulation
Oscillating fans are a good start, but in a room with a dense canopy floor fans may also need to be added.
The goal is to maintain consistency across all portions of a fully grown plant.

Cover Water Tanks and Check Drains
To limit the amount of water that may naturally enter a growing space be sure to cover any water reservoirs you may have.
Also, make sure the drains are actually draining excess water and it is not a large puddle on the floor.
Both may seem obvious, but still worth mentioning.

For Additional Help… Use a Dehumidifier
Dehumidifiers remove moisture from the air.
These units may be need more during the mid to late portions of the growing season because of the increase in plant matter.
Make sure it is a commercial grade (not a residential/homeowner) dehumidifiers
Residential models while cheaper, are also electrically inefficient, and can not hold up under the workload of a grow room
A proper dehumidifier will save money in the long run through proper humidity control and as a result reduce potential loss for disease.

Where Does the Humidity Come From?
Plants transpire about 97% of the water they absorb
Growers are suggested to have multiple units to properly regulate humidity
Multiple units offer more even control over a large grow space and also redundancy so if one unit fails the entire grow space does not fail with it.

To Increase Humidity
A humidifier can produce a constant flow of water vapor for an indoor garden which may be needed if the natural air is especially dry.
Cool water is used to create a mist that disperses throughout the space and increases moisture levels.

Avoid Competing Systems
Getting both the temperature and humidity in balance can be a difficult task.
However, knowing the natural condition of your outside air you may want to adjust light cycles to be during the natural night of the day to reduce the heat of the lights compounding the heat of the day.

Link to Lecture Slides:

*Due to the description character limit the full work cited for “Regulating Humidity in a Cannabis Grow Facility” can be viewed at…


Leave a comment

Your email address will not be published. Required fields are marked *