Quick answer: In a research greenhouse, humidity control serves the experiment. Each humidity treatment needs its own air volume (a compartment, room or chamber) with independent control, because plants sharing one air space are one treatment no matter how many there are. Hold tolerances the study needs (often within a few % RH), log temperature, RH and equipment states at canopy level on one clock, and report conditions with the results. Dehumidifiers must be sized for the worst night load of each compartment, controlled locally, and must not share air paths between treatments.
Quick answer
- One treatment = one independently controlled air volume.
- Log canopy conditions and equipment states together; report them with results.
- Size equipment per compartment, for the worst night load, with fine control.
Define the treatment boundary
| Situation | Independent treatments? |
|---|---|
| Separate compartments with their own vents, heating and dehumidification | Yes |
| Bays divided by curtains with a shared air system | No, unless air paths are truly separated |
| Several benches in one room | No; they are replicates within one treatment |
| Growth chambers with their own conditioning | Yes |
Map doors, vents, ducts, returns, fans, drains and any shared equipment before the study. The research team and statistician decide replication; facility staff document what each plant actually experienced.
Tolerances and stability
Research often needs tighter and steadier conditions than production:
- RH within a few percent of setpoint, with limited excursions.
- Stable day–night transitions, timed consistently every day.
- No large swings when doors open or irrigation runs.
Small dehumidifiers with modulating or staged control, and dedicated humidifiers where treatments need high humidity, give finer control than one large unit cycling on and off.
Measuring and reporting
- Aspirated sensors at canopy height in each compartment; calibrate before and after the study.
- Log at 1–5 minute intervals.
- Record equipment states (vents, heating, dehumidifier, humidifier, irrigation, door) on the same clock.
- Report the measured conditions (means and ranges) with the results. Plant science groups follow guidelines for measuring and reporting the environment of controlled-environment studies, such as those developed by the NCERA-101 committee on controlled environment technology.
See greenhouse humidity sensor placement.
Diagnosing drift
If a compartment drifts from its humidity target:
- Check the sensor against a reference.
- Look at the timeline: irrigation, door openings, light changes, outside weather.
- Check for shared air: a common return or open door between compartments.
- Check equipment: is the dehumidifier running, draining and reaching its capacity at that condition?
- Only then change setpoints or equipment.
Specifying dehumidifiers for research compartments
| Requirement | Specify |
|---|---|
| Capacity | Worst night load of each compartment at its treatment condition |
| Control | Local sensor at canopy; modulating or staged output; fine deadband |
| Air distribution | Even across benches; no direct jets on plants |
| Isolation | No air shared between compartments; separate drains |
| Data | Run and fault signals to the logging system |
| Low-humidity treatments | Desiccant units if dew points below about 5 °C are needed |
Our ceiling-mounted and ducted dehumidifiers and greenhouse dehumidifiers cover compartment sizes from small rooms to full bays; see how to choose a greenhouse dehumidifier.
FAQ
Frequently asked questions
How do you control humidity in a research greenhouse?
Give each treatment its own compartment with independent dehumidification or humidification, sensors at canopy height and continuous logging.
Can different humidity treatments share one greenhouse room?
Not as independent treatments. Plants in one air space experience one humidity condition.
How precisely should research greenhouse humidity be controlled?
As the study requires, often within a few % RH; record and report the measured conditions.
Sources
- NCERA-101, Guidelines for measuring and reporting environmental parameters for plant experiments in growth chambers.
- ASHRAE Handbook—Fundamentals, Psychrometrics.
