Moisture sensors for vegetable cultivation and greenhouses: reliable measurements in high humidity

Author: T. Graf

In this article, we have examined in detail why sensors for high humidity are indispensable in demanding environments and what challenges arise when the air is nearly saturated (> see the article “High Humidity AFTF 35 / KFTF 35”).

But how does this play out in practice?

A particularly sensitive application area is vegetable cultivation, especially in greenhouses and controlled-environment agriculture facilities. Here, high humidity, irrigation, and temperature fluctuations quickly lead to condensation—with direct effects on measurement accuracy, the plant microclimate, and yield.

In this article, you’ll learn how these challenges in vegetable cultivation can be effectively managed—and why robust, specialized humidity and temperature sensors play a crucial role in this process. 

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In a nutshell

In vegetable cultivation, high humidity, irrigation, plant transpiration, and fluctuating temperatures all come into play. This creates challenging conditions for humidity measurement—especially in greenhouses, growing rooms, and controlled growing environments.

Condensation-protected humidity and temperature sensors help reliably measure humidity and temperature and ensure more stable climate control.

Typical benefits:

  • reliable measurements at high relative humidity
  • better assessment of condensation risks
  • Support for ventilation, cooling, heating, and dehumidification
  • Suitable for greenhouses, grow rooms, and controlled growing environments
  • Easy integration into building management systems, DDC, or HVAC controllers

Contents

Why Moisture Measurement Is So Important in Vegetable Farming Common Challenges in Greenhouse and Vegetable Farming What metrics are relevant in vegetable cultivation? AFTF-35 or KFTF-35—which model is best suited for vegetable cultivation? Installation and Measurement Point

Applications in Vegetable Production & Controlled Environments

In vegetable cultivation, humidity is a key factor influencing the plant microclimate, growth, and process stability. Especially in greenhouses, controlled-environment facilities, and vertical farming systems, irrigation, evaporation, ventilation, and temperature fluctuations create highly dynamic conditions.

Typical applications include:

  • Greenhouses with tomatoes, cucumbers, bell peppers, or leafy vegetables
  • controlled growing environments and vertical farming facilities
  • Pre-conditioning and Cooling After Harvest
  • Areas adjacent to greenhouses, utility rooms, or air ducts

High relative humidity, temperature gradients, and localized areas of high humidity can occur particularly in these areas. As the temperature drops, relative humidity rises rapidly—and if the temperature falls below the dew point, condensation can occur. This not only affects building components and surfaces but can also influence the measurement accuracy of conventional humidity sensors.

For operators, this means that ventilation, heating, cooling, and dehumidification can only be controlled effectively if humidity and temperature are reliably monitored. This helps maintain more stable environmental conditions—a key factor for plant quality, yield, and efficient facility operation.

Why Moisture Measurement Is So Important in Vegetable Farming

In vegetable cultivation, humidity directly influences the plant microclimate. It affects evaporation, transpiration, leaf surfaces, temperature regulation, and the risk of condensation. Especially in dense plant stands or enclosed greenhouses, local zones of high humidity can form that differ significantly from the general air conditions in the space.

If the air is too dry, evaporation increases. Plants may experience greater stress, so irrigation and climate control must be adjusted accordingly. If the humidity remains very high for an extended period, the risk of condensation on cold surfaces and plant parts increases. This can create unfavorable conditions for plant quality, crop management, and operational safety.

Reliable humidity and temperature measurements help detect these conditions early on and allow for more precise climate control.

Common Challenges in Greenhouse and Vegetable Farming

In vegetable cultivation, the most challenging conditions often arise not during stable, continuous operation, but during changing climatic phases. Irrigation, evaporation, ventilation, and the Tag-night cycle often cause temperature and humidity to change very rapidly. It is precisely during these phases that the sensor system must provide reliable measurements.

Typical influencing factors include:

  • Irrigation and Evaporation: After irrigation, the humidity in the crop often rises significantly.
  • Tag-Night Cycle: As the temperature drops, relative humidity rises. If the temperature falls below the dew point, condensation may occur.
  • Ventilation and Airflow: Windows, fans, air circulation systems, and air conditioners create different air movements and localized areas of humidity.
  • Dense vegetation: The microclimate between rows of plants may differ from that in the open greenhouse space.
  • Cleaning and Spray Mist: Wet surfaces or moisture spikes can further affect measurement conditions.

Conventional humidity sensors can reach their limits in such situations. If condensation forms on the sensor element, this often results in sluggish readings, longer recovery times, or inaccurate control signals. Condensation-protected humidity and temperature sensors reduce this risk and help ensure more stable readings during critical periods of high humidity.

This way, the climate control system does not rely on momentary readings or distorted humidity signals, but can base ventilation, heating, cooling, or dehumidification on more reliable measurements.

What metrics are relevant in vegetable cultivation?

When it comes to climate control in vegetable cultivation, it is not just individual measurements that are crucial, but how they interact. Temperature fluctuations, irrigation, and plant transpiration, in particular, can quickly change the relative humidity.

Key metrics include:

  • Relative humidity—a key control variable for plant climate and humidity management
  • Temperature – directly affects how much moisture the air can hold
  • Dew Point – Helps Assess Condensation Risks
  • Absolute humidity – indicates the actual water content of the air
  • Mixing Ratio – Helps Evaluate Ventilation and Dehumidification Processes

The AFTF-35 and KFTF-35 measure humidity and temperature and can provide additional calculated parameters for building management systems, distributed control systems, climate control computers, or warehouse technology.

AFTF-35 or KFTF-35—which model is best suited for vegetable cultivation?

Depending on the system, both room sensors and duct sensors can be used for vegetable cultivation. The key factor is where the measurement data is needed for climate control.

AFTF-35 (Surface-Mounted Sensor)

  • Wall mounting in rooms
  • Ideal for warehouses and cold storage rooms
  • Direct measurement of indoor air

The AFTF-35, as a surface-mounted sensor, is suitable for directly measuring the ambient air in greenhouses, cultivation rooms, or technical auxiliary areas. It is installed on a suitable mounting surface and provides measurement values where the climate needs to be monitored or controlled.

KFTF-35 (Duct Sensor)

  • Installation in Air Ducts
  • includes mounting flange
  • for ventilation and air conditioning systems

The KFTF-35 duct sensor is used in ventilation or air-conditioning ducts. It is useful for measuring humidity and temperature in supply or exhaust air ducts, recirculation systems, or central air-handling units.

In more complex greenhouse systems, it may be useful to combine both sensors: The duct sensor indicates which air is being supplied or exhausted. The room sensor indicates the actual conditions in the growing area.

Installation and Measurement Point

The measurement location should be chosen so that it provides as representative a picture as possible of the actual plant and indoor climate. For the AFTF-35, a readily accessible location with sufficient air movement is recommended—not directly next to heating pipes, not immediately in the airflow from fans or air conditioners, and not in areas heavily affected by spray water or local humidity spikes.

The KFTF-35 is installed as a duct sensor in ventilation or air-conditioning ducts using the mounting flange provided. Before installation, ensure that the measurement range, installation length, duct dimensions, flow velocity, and protection class are suitable for the application.

Important: The AFTF-35 and KFTF-35 are designed for high-humidity environments, but are intended only for use with non-contaminated, non-condensing air and without positive or negative pressure at the sensor element. Installation and commissioning must be performed only by qualified personnel. For specific installation, always follow the instructions in the operating and installation manual.

Integration with greenhouse control systems, building automation systems, and DDC

The AFTF-35 and KFTF-35 can be easily integrated into existing control and automation systems using standard signals. Depending on the model, active outputs are available as 0–10 V or 4–20 mA. This allows relative humidity, temperature, and an additional calculated parameter to be transmitted to a building management system (BMS), DDC, PLC, or HVAC computer.

This is particularly helpful in vegetable cultivation because climate control does not rely solely on relative humidity. Additional parameters such as dew point, absolute humidity, or mixing ratio help provide a better assessment of ventilation, dehumidification, and condensation risks.

This allows heating, ventilation, cooling, and dehumidification to be based on reliable measurements—with the goal of creating stable growing conditions and managing climate fluctuations more effectively.

Bestseller AFTF-35 / KFTF-35

HYGRASGARD® AFTF-35-I/W
°C
%RH

On-wall humidity and temperature sensors

HYGRASGARD® AFTF-35-I/W

790,69 €
790,69 €
HYGRASGARD® AFTF-35-U/W
°C
%RH

On-wall humidity and temperature sensors

HYGRASGARD® AFTF-35-U/W

790,69 €
790,69 €
HYGRASGARD® KFTF-35-U/W LCD
°C
%RH

Duct humidity and temperature sensor

HYGRASGARD® KFTF-35-U/W LCD

903,63 €
903,63 €
HYGRASGARD® KFTF-35-U/W
°C
%RH

Duct humidity and temperature sensor

HYGRASGARD® KFTF-35-U/W

790,69 €
790,69 €
HYGRASGARD® KFTF-35-I/W LCD
°C
%RH

Duct humidity and temperature sensor

HYGRASGARD® KFTF-35-I/W LCD

903,63 €
903,63 €
HYGRASGARD® KFTF-35-I/W
°C
%RH

Duct humidity and temperature sensors

HYGRASGARD® KFTF-35-I/W

790,69 €
790,69 €
HYGRASGARD® AFTF-35-U/W LCD
°C
%RH

On-wall humidity and temperature sensors

HYGRASGARD® AFTF-35-U/W LCD

903,63 €
903,63 €
HYGRASGARD® AFTF-35-I/W LCD
°C
%RH

On-wall humidity and temperature sensors

HYGRASGARD® AFTF-35-I/W LCD

903,63 €
903,63 €

FAQ

Which moisture sensor is best suited for growing vegetables?

Condensation-protected humidity and temperature sensors are suitable for vegetable cultivation, greenhouses, and controlled-environment growing facilities. They are particularly helpful in situations involving high humidity, irrigation, temperature fluctuations, or the risk of condensation.

Why is humidity so important in a greenhouse?

Humidity affects the plant environment, evaporation, and the risk of condensation. Accurate measurements help regulate ventilation, heating, cooling, and dehumidification.

Where should a humidity sensor be installed in a greenhouse?

The sensor should be mounted in a representative location with sufficient air movement. Avoid direct heat sources, direct airflow from fans or air conditioners, and areas with water spray or high localized humidity spikes.

Why is the dew point important in vegetable gardening?

The dew point helps determine when condensation may occur. This is particularly important during Tag-Tag temperature fluctuations, high humidity, and when there are cold surfaces in the greenhouse.