Marijuana plants are extremely sensitive. If the humidity levels are too high or too low, the plants become at risk of disease and are unlikely to grow to their full potential. When designing HVAC systems for grow rooms, it is critical to identify and maintain the right humidity levels or the grow room could suffer a great loss.

While amateurs use a variety of hacks to control humidity levels, HVAC techs and designers are able to create systems around certain types of HVAC units that make maintaining the humidity control much easier.

How Humidity Affects Marijuana Plants

Like most plants, marijuana takes in water from its roots and leaves. The higher the humidity, the more water marijuana plants absorb through their leaves and the less water is absorbed through the roots. In low humidity environments marijuana plants will absorb more water through their roots and less through their leaves.

Why does this matter?

Growers infuse the water with critical nutrients that will be absorbed through the plant’s roots. If the humidity level is too high, the plants will not get enough of these nutrients. Certain diseases, such as white powdery mildew and bud rot, are also more likely to strike the leafy plants in high humidity conditions.

But, if the humidity level is too low, the plants will absorb too many nutrients which will harm their growth.

Additionally, marijuana plants need different levels of humidity during different stages. Proper humidity control is one of the most important aspects in raising a healthy crop as quickly as possible.

The general rule of thumb is that younger marijuana plants do best with high humidity and more mature plants need lower humidity levels.

Here is a general reference chart for humidity levels, but please note that specific strains may have different needs:

  • Clone stage needs 70-80% humidity
  • Vegetative stage needs 40-60% humidity
  • Flowering stage needs 40-50% humidity
  • Final weeks of flowering less than 40% humidity

How Air Flow and Temperature Affect Humidity and Plant Growth

Even during the stages when the marijuana plants need high levels of humidity, they are not out of harm’s way. In fact, they are still at risk for mold and mildew. The plants must receive regular airflow from around the roots and undersides of the leaves to prevent these diseases.

Air flow is also critical because CO2 is important for plant growth, but without good airflow it will all settle at the grow room floor.

Temperature also affects humidity. Often new growers install the wrong size of HVAC units. When the units are oversized for the space, they tend to cycle on and off in short cycles. These short cycles create temperature and humidity spikes, causing erratic conditions that do not allow the plants to thrive.

Undersized units are also not ideal, as they enable temperatures to get too hot, which also affects humidity levels. Grow rooms already have powerful electric lights that contribute to temperature increases, so adding degrees is unnecessary, yet often overlooked in HVAC design.

Why Air2O is the Best Solution for Grow Room Humidity Management

Traditional HVAC units tend to be the source of many temperature, air flow, and humidity issues. Grow rooms are typically better served with a hybrid and Indirect-Direct Evaporative Cooling (IDEC) system that uses 80% less energy than traditional HVAC units.

Air2O offers such systems that are designed to control both airflow, humidity, and temperature without being dependent on secondary systems or additional equipment. These systems also make it much easier to adjust humidity levels as the plants go through different parts of their cycle.

Read more about Air2O’s cooling system technology and ensure your grow room continues to operate optimally.