A greenhouse humidity difference becomes useful when its locations and time basis are clear. Compare simultaneous readings with simultaneous readings, and period averages with equivalent averages, before deciding what a “wet zone” means.
Averages can preserve spatial differences
A 2014 study used 100 wireless sensors across six commercial-greenhouse experiments with different crops and conditions. Horizontal temperature and RH differences appeared in instantaneous observations and persisted in five-day averages. The authors called for further work before integrating the findings into controls or quantifying energy savings. (Wageningen study)
Height changes the comparison
A 2022 Venlo-greenhouse study measured five spatial locations, four canopy heights, and ground and roof positions. Its largest vertical deviation in average hourly RH occurred at 1 p.m.: 76.90% at the lower canopy and 71.74% in the upper air. These are paired study observations, not recommended targets or a universal vertical gradient. (Original journal abstract)
Read a site chart before assigning a cause
Label each trace with its sensor location and height, and keep the averaging interval visible. A brief local peak and a sustained difference answer different questions; an average can conceal the timing of a peak even when a persistent location difference remains visible.
For example, compare a lower-canopy afternoon reading with an upper-air reading from the same period before describing a vertical difference. Do not compare it with a different day's whole-house average and treat the result as a measured gradient.
Use the sensor-placement guide for practical measurement context. Investigate an observed pattern before turning it into an equipment-sizing or control decision; these studies provide no site commissioning tolerance.
Related project questions
Zone measurements can inform layout review and crop-specific questions. Continue with direct-air and duct-connected equipment layouts and tomato pollination conditions. For the wider project context, return to agricultural humidity control.
