Humidity Control in Commercial Grow Rooms

Controlling humidity in a commercial grow room is critical for maximizing yields, preventing mold, and ensuring plant health across all growth stages.

 

Why Humidity Control Matters in Commercial Grow Rooms

If your commercial grow room has a high plant density, it will cause high transpiration, which means high humidity.

The high humidity will increase the risk of mold and bud rot, especially in the flowering stage.

If your grow room has a poor RH, it will cause environmental stress, which results in stunted growth, pests, and lower yields of your crops.

Proper humidity control helps keep the consistency of your grow room, especially important in regulated industries (e.g., cannabis, hydroponics).

 

Optimal Humidity by Growth Stage

Growth Stage:	Ideal RH:	Notes:
Seedlings	65–70%	Encourages strong root development
Vegetative	50–70%	Boosts growth, RH can be a bit higher
Early Flower	45–55%	Lower RH to reduce mold risk
Late Flower	40–50%	Crucial to prevent bud rot
Curing	45–55%	Maintains aroma, avoids overdrying

 

Key Components for Humidity Control in Commercial Grow Rooms

1. Industrial-Grade Dehumidifiers

Capacity: 145 to 500+ pints/day

Type: wall mounted refrigerant dehumidifiers for large spaces

Brands: Quest, Preair

Pro Tip: Choose a dehumidifier for greenhouse that allows ducting and external drainage for uninterrupted operation.

 

2. HVAC Integration

Install dedicated HVAC systems that manage temperature and humidity together.

Use variable-speed drives to match changing loads throughout the day and plant cycles.

 

3. Automated Environmental Controllers

Systems like TrolMaster, IntelliDrive, or Growlink can:

Monitor RH, temp, CO₂, light, VPD

Turn on/off dehumidifiers, humidifiers, ACs, and fans

Send real-time alerts

Cloud dashboards enable remote control and monitoring

 

4. Air Circulation and Ventilation

Use oscillating fans to mix air and prevent micro-climates.

Ducted intake/exhaust systems reduce stagnant air pockets.

Airflow must be uniform across the canopy and under the benches.

 

5. Zoning by Room or Growth Stage

Inside the grow room, dividing the facility into climate zones (e.g., veg rooms, flower rooms, mother rooms) is a wise option.

It is better to have independent control of RH, temp, and light for each stage for precision control.

 

Advanced Humidity Strategies

1. Use Vapor Pressure Deficit (VPD)

VPD is a better way to dial in humidity based on temp and plant growth stage

VPD range for optimal growth: 0.8–1.2 kPa

Automate with VPD sensors linked to controllers

 

2. Nighttime RH Management

Transpiration slows at night → humidity rises

Set the cannabis dehumidifier to increase output during lights-off

Maintain air movement even when the lights are off

 

3. Redundant Systems

Have backup dehumidifiers or HVAC to avoid catastrophic failures during peak bloom

Use sensors to trigger alerts for high RH spikes

 

Summary

Component:	Why It Matters:
Large-Capacity Dehumidifiers	Main humidity control engine
HVAC with RH Integration	Temperature + humidity balance
Environmental Controller	Automation + alerts + consistency
Air Movement System	Eliminates microclimates
Drainage Infrastructure	Handles continuous condensate flow
Smart Sensors + VPD Monitors	Precision control at the plant level