How to Control Humidity in Greenhouses: Methods and IoT Solutions
- Nguyen Nhut Quy
- 3 days ago
- 7 min read
Why is it so difficult to keep the air inside a greenhouse at the right balance? For many growers, humidity is the most unpredictable factor. Too much moisture encourages fungal diseases, while dry air stresses plants and reduces yields.
Recent research from the UK Met Office reinforces how critical humidity really is. Their new HadISDH.extremes dataset shows that global humid heat extremes have been rising steadily since the 1970s—by around 0.2°C per decade worldwide, and even faster in Europe during summer months. These so-called “stealth heat events” reveal that humidity, not just temperature, is a driving force behind human health risks and reduced productivity. If humidity can make entire regions less habitable for people, imagine its effect on delicate greenhouse crops.
That is why greenhouse humidity control has become one of the most important aspects of modern agriculture. In this guide, we will explore why humidity matters in greenhouses, practical methods growers use to control it, how humidity control systems work, and how advanced IoT solutions such as wireless sensors can make the process easier, more accurate, and more reliable.
Why Humidity Matters in Greenhouses
In a controlled greenhouse environment, humidity is one of the most decisive yet unstable variables. Relative humidity (RH) describes the amount of water vapor in the air compared with the maximum it can hold at a given temperature. Even small deviations from the optimal range—typically 60–80% RH for most crops - can create cascading problems for both plants and infrastructure.
Plants regulate water through transpiration. If RH is too low, water evaporates rapidly from leaf surfaces, forcing plants to overcompensate by drawing more moisture from their roots. This leads to wilting, nutrient uptake imbalance, and reduced photosynthesis. When RH is too high, the opposite occurs: transpiration slows, nutrient movement inside the plant stalls, and leaves become more susceptible to fungal infections such as powdery mildew, botrytis, or downy mildew.
Excess humidity during flowering stages reduces pollen viability and hampers fertilization. For example, tomatoes require around 65–75% RH for optimal pollination—too much or too little humidity directly lowers fruit set. In cucumbers, high RH (>85%) encourages fruit deformities, while leafy greens suffer tip burn if RH falls below 50%.
Unstable RH often forces growers to run ventilation, heating, or misting equipment longer than necessary, driving up energy bills. Condensation from excess humidity also leads to heat loss, as wet surfaces transfer energy faster than dry ones.
Persistent condensation corrodes metal frames, damages electrical fixtures, and increases the risk of biofilm formation on surfaces. Long-term exposure to high humidity reduces the lifespan of greenhouse structures and equipment.
How to Control Humidity in Greenhouse
Controlling humidity in a greenhouse is not about a single action—it is about orchestrating multiple strategies so that the air, plants, and infrastructure stay in balance. Each method has its own mechanism, limitations, and best-case application.
One of the most fundamental approaches is ventilation. By exchanging indoor air with drier outdoor air, growers can reduce relative humidity quickly and effectively. Natural ventilation through roof vents and sidewalls works well in mild climates, while mechanical ventilation with exhaust fans is essential when outside conditions are less favorable. The challenge, however, is that ventilation also changes temperature, and in colder seasons it can increase energy demand.
Heating is another classic method. Warmer air holds more moisture, so when a greenhouse is heated, the relative humidity drops. This method is especially valuable at night or during winter, when humidity tends to accumulate and condensation forms on cold surfaces. Still, heating alone is not a full solution; it must be paired with ventilation to actually remove the excess moisture instead of simply redistributing it.
More advanced facilities make use of cooling and misting systems. High-pressure fogging not only regulates leaf temperature but also prevents sudden drops in humidity that could stress the plants. However, without precise control, misting can raise humidity to critical levels and create a breeding ground for fungi. That is why professional greenhouses rely on sensors and controllers to fine-tune misting cycles.
Airflow inside the greenhouse is equally important. Air circulation fans prevent localized humidity pockets where condensation forms and disease outbreaks begin. Uniform airflow means that the entire crop experiences a stable microclimate rather than one section being too dry while another is overly damp.
Finally, irrigation practices must be considered. Overwatering, particularly late in the day, leaves excess moisture on plant surfaces and soil, raising humidity overnight when ventilation is minimal. Smart irrigation scheduling—such as watering in the morning or using drip systems—helps manage humidity at its source.
In high-value crop production, some growers invest in dehumidification systems. These units actively remove water vapor from the air and are particularly useful in northern climates or sealed, high-tech facilities where external air exchange is limited. While energy-intensive, they provide unmatched precision.
Ultimately, no single method is sufficient on its own. Effective humidity control in greenhouses is the result of integrating ventilation, heating, cooling, circulation, and irrigation into a coherent climate management strategy, often enhanced by automated controls and in-time sensor data.
Greenhouse Humidity Control Systems
While traditional methods like ventilation and heating provide growers with basic ways to influence humidity, they are often reactive and imprecise. Commercial greenhouse operators increasingly turn to integrated humidity control systems that combine measurement, decision-making, and automated action.
At the heart of such a system are humidity and temperature sensors. These sensors continuously capture in-time data on the microclimate around the crop canopy. The information is then sent to a central controller or directly to a cloud-based platform. Based on predefined thresholds, the controller can trigger fans, vents, heaters, or foggers to keep relative humidity within the desired range.
A complete greenhouse humidity control system usually includes:
Sensors (Nodes): Accurate humidity and temperature measurements at multiple points in the greenhouse.
Controller: A programmable logic controller (PLC) or IoT gateway that interprets sensor data and executes commands.
Actuators: Mechanical devices like exhaust fans, roof vents, heaters, or misting valves that physically alter the environment.
Software platform: For monitoring, data logging, and remote access, often with mobile alerts.
The strength of these systems lies in automation. Instead of relying on manual checks and adjustments, growers can ensure a stable environment day and night. Automated systems also prevent human error, optimize energy use, and allow operators to manage larger greenhouse areas with fewer staff.
For smaller facilities, simple stand-alone controllers may suffice. They activate fans or heaters when humidity crosses a set limit. Larger, high-tech greenhouses, however, integrate humidity control with lighting, CO₂ enrichment, and irrigation scheduling, creating a comprehensive climate control strategy.
Ultimately, the move toward system-based management reflects the shift from intuition-driven farming to data-driven agriculture. By linking sensors and controllers, growers gain a level of consistency and precision that manual methods cannot achieve.
Temperature and Humidity Control Together
Inside a greenhouse, temperature and humidity are inseparable. Any change in one directly affects the other because the amount of water vapor air can hold increases with temperature. Warmer air can absorb more moisture, while cooler air quickly reaches saturation, leading to condensation. For this reason, growers who focus only on temperature or only on humidity often face unexpected problems.
Take the case of tomatoes: if air is too warm but humidity is too low, plants transpire excessively, pulling calcium unevenly through the tissues and leading to blossom-end rot. Conversely, if humidity is too high during warm nights, pollen becomes less viable, reducing fruit set. The ideal environment for tomatoes is a balance of 65–75% RH at moderate temperatures.
Cucumbers provide another example. They thrive in a warm, moist atmosphere with 70–80% RH. If the temperature rises without proper humidity management, the leaves become stressed, and fruit quality declines. But if humidity remains above 85% at warm temperatures, the crop becomes vulnerable to downy mildew outbreaks.
This interdependence is why many growers search for “greenhouse temperature and humidity control” rather than treating the two factors separately. Modern climate control systems often link both variables within the same feedback loop. A controller may increase ventilation to reduce humidity, but if the air temperature drops too quickly, it can also activate heating to maintain balance. Similarly, fogging systems are programmed not just for cooling but for stabilizing relative humidity.
Ultimately, temperature and humidity must be managed as a pair. Stable conditions protect plant physiology, reduce disease pressure, and create a predictable environment that supports consistent yields. Growers who integrate both into a single management strategy move beyond trial-and-error and gain the ability to fine-tune their greenhouse climate with confidence.
Modern IoT Solutions (Daviteq’s Approach)
Traditional greenhouse humidity control relies on mechanical systems, but today’s growers require more than manual switches and fixed schedules. They need in-time data, remote monitoring, and automated decision-making. This is where IoT-enabled wireless sensors transform greenhouse management.
By integrating WSLRW-ATH or WSSFC-ATH into greenhouse operations, growers can shift from reactive management to predictive and automated climate control, ensuring healthier plants and higher yields with less manual effort.
Effective greenhouse humidity control is no longer just about opening vents or turning on heaters. As climate conditions grow more unpredictable, growers need reliable systems that integrate temperature and humidity management into one strategy. By combining proven methods with IoT-enabled wireless sensors, greenhouse operators can maintain optimal conditions for crops, improve yields, and reduce operational costs.
Daviteq’s LoRaWAN (WSLRW-ATH) and Sigfox (WSSFC-ATH) humidity and temperature sensors provide growers with accurate, long-term monitoring and easy integration into automation platforms. With in-time data and predictive control, your greenhouse can shift from reactive adjustments to smart, data-driven management.
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