The following guidelines provide the necessary information to operate DryGair dehumidifiers effectively and efficiently
To allow maximum efficiency, DryGair is designed to control humidity according to plants’ night time transpiration rate.
These guidelines offer the best operation method for DryGair – to provide dehumidification at times when the traditional solution of ventilation is ineffective or inefficient. These periods include night time, rain or cloudy weather.
Guidelines may differ, depending on climate set points and facility operation. For specific guidelines for your growing facility, contact our team of experts.
Common Operating Method
* Operate DryGair as needed. On cloudy and rainy days, the air outside is more humid, making ventilation inefficient and less effective. DryGair should be activated when necessary.
The Importance of Night Time Humidity Control
Plants transpire 24/7, releasing water vapor into the air, even during the night. Simultaneously, temperatures drop during the night, leading to higher relative humidity.
This is due the physical properties of air – at lower temperatures, air can hold less water. When the air can’t carry the amount of water vapor present in the greenhouse, water begins to condense, appearing on different surfaces.
Water condenses on the coolest surfaces, forming on structural elements such as railings, equipment and even on the leaves themselves. This presence of water is what triggers disease and mold development, such as powdery mildew or gray mold.
Night Time DryGair Operation Guidelines
In order to prevent dew point condensation during the night, the greenhouse must be completely closed, including vents, and deployed thermal screens, if applicable.
The DryGair system should operate throughout the night, from the late afternoon to the early morning.
At 18°C (64°F) and 80% RH, DryGair extracts 45 liters (12 gallons) of water per hour, from the greenhouse air. This ensures optimal humidity levels throughout the night.
DryGair’s patented air circulation fanning system works simultaneously to ensure uniform climate conditions throughout the greenhouse, preventing humid microclimates from forming.
DryGair extracts more water than any other greenhouse dehumidifier!
The Importance of Day Time Humidity Control
In the morning, as the sun rises, the radiation hitting the plants increases. The presence of sunlight during the day stimulates photosynthetic activity, leading to increased transpiration. Transpiration during the day can reach as much as ten times higher than during the night.
Simultaneously, as greenhouse temperatures rise, additional water vapor is released from the soil, further increasing the amount of water vapor in the greenhouse during the day time.
The traditional method of day time humidity reduction is ventilation – releasing the humid air from the greenhouse. If weather outside is comfortable (i.e., not humid, rainy, or too cold), this method can achieve very good results with minimal energy requirements.
However, when weather outside isn’t favorable, it’s highly inefficient to ventilate.
When heating the greenhouse, releasing air means losing heat. So, while ventilating, growers must constantly run their heating system, in order to make up for the lost heat, and maintain optimal temperatures for the plants. This is a highly wasteful, expensive, and environmentally harmful practice.
In addition to being inefficient, ventilation is sometimes ineffective, meaning no humidity reduction is achieved, despite the exchange of air.
The most efficient way to reduce humidity during humid, rainy, cloudy, or cold days, is to close the greenhouse and operate DryGair as necessary. DryGair may also be used to supplement ventilation during the day.
Due to heightened evaporation levels during the day, it’s important to monitor humidity levels, and operate accordingly.
During sunrise and sunset, if necessary, DryGair may be supplemented with ventilation.
Sunrise: Once the plants receive solar radiation, transpiration is rapidly sped up, though temperatures remain low from the night. This causes a sudden spike to relative humidity.
DryGair should remain operational, even if ventilating, to help treat the high quantities of water vapor during sunrise.
Sunset: When the sun sets, temperatures quickly drop, causing a spike in relative humidity.
DryGair should be turned on before sunset, when the vents are still open, to prevent dew point condensation during this spike.
