Ventilation in a box or greenhouse is responsible not only for fresh air. It affects temperature, humidity, evaporation of water from the substrate and the risk of fungal problems. If the hood is turned on accidentally or too abruptly, the watering schedules also change: the soil dries faster, the sensors show different values, and the plants become stressed.
Good ventilation automation starts with measurements. You need at least the temperature and humidity at the level of the leaves, and not at the ceiling or near the fan. In a large volume, it is useful to have several points: at the air inlet, in the plant area and in the upper warm part. Then you can see what exactly the hood does, and not just the fact that it is turned on.
Where to install sensors
The temperature and humidity sensor should not be placed under direct air flow or near a lamp. In the first case, it will show a local draft, in the second - overheating of the point, and not the plant zone. It is better to choose a place in the shade at crown level, with normal circulation. If the sensor is battery-powered, check how often it updates data: too infrequent updates are not suitable for controlling the hood.
For a greenhouse, it is important to separate day and night modes. During the day, ventilation often struggles with overheating, and at night - with high humidity and condensation. In GrowerHub it is convenient to view graphs by day and compare fan activation with temperature, humidity and watering.
Simple rules are better than sudden switches
The simplest scenario: turn on the hood above the set temperature and turn it off below another, lower limit. This hysteresis is needed so that the fan does not click every half minute near the threshold. For humidity, the logic is similar: turn it on when it is exceeded, turn it off after it decreases with a margin.
If the ventilation is powerful, turn it on in stages or in short cycles. A sharp flow can quickly dry out a small box, and the soil moisture sensor will show an accelerated drop. Therefore, it is useful to consider ventilation together with the article microclimate control in the greenhouse, and not as a separate switch.
Connection with light and watering
Light increases temperature, ventilation reduces humidity, and watering temporarily raises air and soil humidity. These processes are connected. If the hood is turned on immediately after watering, the top layer may dry out faster than the root zone. If the lamp is turned on without ventilation, the temperature rises and the plant evaporates more water.
In GrowerHub it is useful to configure not only automatic actions, but also notifications. For example, “the temperature is above normal when the lights are on” or “the air humidity is high at night for more than two hours.” The history of such events helps to see recurring problems. More information about reading graphs can be found in the article history of microclimate and graphs.
What to check by hand
Automation does not replace inspection. Every few days, check the filter, grilles, fan noise, flow direction and absence of condensation. If the fan is running longer than usual, it could be a sign of clogs, heat, a faulty sensor, or plants that are too crowded.
For Zigbee sensors in a greenhouse, communication is important: metal structures, humidity and distance can degrade the network. If you use wireless devices, check availability and battery charge. There is a separate material on the choice of devices Zigbee for the greenhouse.
Conclusion
Ventilation should maintain a stable environment and not just make noise on a schedule. Place sensors in the right places, use hysteresis, link the hood with light and watering, check schedules and the physical condition of the equipment. Then the microclimate becomes controlled, and not a set of random inclusions.