Indoor cultivation allows growers to modify all the necessary parameters. As a result, plants grow properly and provide a good quality yield. However, a calculation mistake or maintaining incorrect humidity levels for a long time can damage or even ruin the yield completely. Therefore, learning how to lower humidity in a grow tent and knowing the right parameters for every cultivation stage is very important.

In order to adjust parameters correctly, growers must know how to lower relative humidity, as it is crucial for plants’ transpiration, thermal regulation and to prevent fungi or other illnesses.

As the plant grows, it needs less humidity, thus, you’ll need to lower humidity levels to promote proper plant development, which will also reduce the risk of fungi or rotting.

Humidity levels for each cultivation stage

  • Seedlings or rooted cuttings (65-75%): At this moment, plants need to develop and strengthen their roots, for which they need high humidity levels. This way, leaves absorb the water that goes to the roots and promotes their development.
  • Growth phase (50-65%): During this period, roots absorb the necessary water to distribute the nutrients and cool the plant off.
  • Flowering period (40-50%): At this moment, the plant uses all of its energy to create flowers. Humidity is drastically reduced to prevent buds from suffering fungi or bacteria.
lower humidity grow tent cannabis

What is a dehumidifier? How does it work?

Dehumidifiers are devices that absorb environmental humidity from the room where they are installed. Some of them have a deposit that stores the water that they absorb, and when it reaches its limit, it stops automatically. However, most of them include the option to connect them to a bigger deposit or straight into the sewer, which guarantees their constant functioning.

There are other ways to lower humidity in a grow tent, although none of them are as precise as using a good quality dehumidifier:

  • Increasing ventilation
  • Renewing the air in the grow tent constantly
  • Using refrigerated reflectors to control temperature precisely, which influences humidity directly.
lower humidity grow tent

The best dehumidifiers to lower humidity in a grow tent

Cornwall Electronics dehumidifier

Cornwall Electronics dehumidifier is perfect for grow tents. It has a 12 L extraction capacity and a 1.5 L deposit. It also features an outlet hole to attach a tube and drain the excess water straight into the sewer or into a larger tank, which will prevent it from stopping working once the main deposit is full.

Consequently, this device guarantees proper humidity control in grow rooms of up to 20 square meters, greatly reducing the risk of fungi or mold. Perfect for difficult humid areas that are causing growers trouble.


  • Voltage/Frequency: AC 220 V-240 V/ 50 Hz
  • Dehumidifier: (liters per day) 12 L
  • Power consumption: 170 W
  • Tank capacity: 1.5 L
  • Weight: 10.5 kg
  • Size: 290 x 170 x 512 mm
  • Airflow: 448 m3/h
  • Coverage: 15-20 m2
  • Drain outlet size: 9.5 mm
cornwall electronics dehumidifier

50L/Day Industrial Dehumidifier

The industrial dehumidifier is enough to prevent fungi in grow rooms of up to 120 square meters.

Although the deposit capacity holds 5.5 L, it can also be installed straight into the sewer with an included tube. Otherwise, it will automatically turn off when full.


  • Voltage/Frequency: 220-240V/ 50Hz
  • Dehumidifier: 50 L/day (30 ºC, 80% RH)
  • Power consumption: 710 W
  • Rated current: 3.2A (30ºC, 80% RH)
  • Water tank capacity: 5.5 L
  • Net weight/Gross weight: 36/ 39.5 kg
  • Size (width, length, height): 43 x 51.5 x 82.5 cm
  • Airflow: 448 m3/h
  • Coverage: 80-120 m2
  • Sound level: 60 dB(A)
  • Refrigerating charge: R410A/370 g
  • Cable: 2.5 m
  • Drainage tube included.
50L/Day Industrial Dehumidifier

Semi-Industrial Home Dehumidifiers

These dehumidifiers are available in assorted models to suit different grow sizes. As the size of the device increases, so does the speed mode, the quality of the humidistat, the wattage or the deposit.

  • 16 L/Day Dehumidifier: 1 fan speed, analog humidistat, 360 W, 37dB, 58 x 36 x 27 cm, 4 L tank. 10 m2.
  • 30 L/Day Dehumidifier: 1 fan speed, analog humidistat, 500 W, 48dB, 80 x 38 x 32 cm, 6 L tank. 20 m2.
  • 50 L/Day Dehumidifier: 2 fan speeds, screen humidistat, 1030 W, 55dB, 60 x 35 x 36 cm, 6.5 L tank. 40 m2.
  • 105 L/Day Dehumidifier: 2 fan speeds, screen humidistat, 1160 W, 56dB, 99 x 54 x 41 cm, only usable with drain. 80 m2.
Semi-Industrial Home Dehumidifiers

How to measure relative humidity

Once you are aware of the parameters plants need to grow properly, you’ll need a hygrometer to measure relative humidity inside the grow tent.

GB The Green Brand indeed features all sorts of thermo-hygrometers, to suit the different needs growers might have.

Digital Max-Min Sensor Thermo-Hygrometer with probe

This digital thermo-hygrometer is perfect to calculate temperature and relative humidity with great precision and in real time. With this device, you can also know other aspects of the grow, such as the perfect lamp height, thanks to its 1.5 m probe.

Digital max-Min Sensor Thermo-hygrometer with probe Specifications:

  • Measures from -30°C to 70°C.
  • Measures from 25% to 90% of moisture.
  • Works on 1.5 V batteries.
  • Dimensions: 11 cm x 7 cm x 1.5 cm.
  • Size of the screen: 3 cm x 4 cm
higrómetro max min digital con sonda

Benetech Digital-Manual Thermo-Hygrometer

This thermo-hygrometer measures temperature and relative humidity of the grow room with precision. To sum up, it is also silent and easy to transport thanks to its reduced size.

  • Benetech digital-manual thermo-hygrometer details:
  • Temperature range: -10ºC to 50ºC
  • Temperature precision: +/-1ºC, 1.8ºF
  • Humidity range: 5-98%
  • Precise humidity: +/-3% between 30-95% and +/-5% between 10-30%
  • Humidity Resolution: 0.1% Rh
  • Readings: 2.5 times per second
  • AA batteries not included.
Benetech Digital-Manual Thermo-Hygrometer
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Erik Collado

With more than 10 years of background in the cannabis sector, his experience and knowledge are the base of GB The Green Brand’s success

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