Quick answer: Commissioning greenhouse humidity control proves that the installed system holds the agreed crop condition during the periods that cause trouble: nights, dusk and dawn, after irrigation, and with screens closed. A midday check doesn't do that. Agree a measurable acceptance condition first. Then verify sensors, the sequence between heating, venting, screens and dehumidifiers, air distribution across the crop, drainage and alarms, and record several days of trend data before handover.
Quick answer
- Acceptance condition: target, measurement point, time window, tolerance.
- Test the risk periods (night, dusk/dawn, screens closed).
- Hand over trend data, settings, alarms and a correction process.
1. Acceptance condition
| Item | Example format |
|---|---|
| Target | e.g. RH ≤ 85 % or dew point ≥ 2 K below leaf temperature |
| Measurement point | Canopy height, representative zones |
| Time window | 20:00–08:00, screen-closed period |
| Tolerance | Normal range, warning, alarm |
| Exclusions | Doors open, maintenance, power cut, abnormal irrigation |
2. Sensors
- Located at canopy height, shaded and aspirated, away from dehumidifier discharge and heating pipes.
- Compared against a calibrated reference at the start; record the offset.
- Enough zones to represent the house (ends, middle, near walls).
See humidity sensor placement and calibration.
3. Equipment and sequence
| Check | Pass if |
|---|---|
| Dehumidifiers start on humidity demand | They start at the agreed setpoint and stage in order |
| Heating interaction | Heat and dehumidification don't fight, e.g. heat doesn't rise just to lower RH when the dehumidifier can |
| Vent interaction | Vents don't open while dehumidifiers run, unless the sequence allows heat-and-vent |
| Screens | Closing the screen triggers moisture control as expected |
| Deadband | No rapid on–off cycling; see automated humidity control |
| Climate computer interface | Commands, status and alarms exchanged correctly |
Related: automated humidity control.
4. Night and transition tests
- Trend at least several nights in the risk season.
- Watch dusk: does moisture removal start before RH rises?
- Watch dawn: is leaf temperature kept above the dew point as the sun comes up?
- After irrigation: how fast does RH return to target?
See greenhouse night-time humidity.
5. Air distribution
- Compare RH and temperature across zones; record the spread.
- Check dry air reaches the canopy (smoke or anemometer at plant level).
- HAF fans run in the agreed pattern.
6. Drainage, power, faults
- Condensate drains with fall and doesn't drip on crops or paths.
- Power supply and protection match the design.
- Simulate faults: unit trip, sensor failure, communication loss. Alarms reach the grower.
7. Handover package
- As-built layout, settings, sequence description
- Sensor calibration records
- Trend data from the test period
- Alarm list and test results
- Maintenance plan (filters, coils, drains, sensors)
- Open issues and correction actions
Our greenhouse dehumidifiers are supplied with controls documentation for the climate-computer interface.
FAQ
Frequently asked questions
How long should greenhouse humidity commissioning take?
Long enough to record several nights in the risk season, plus fault and alarm tests.
Where should humidity sensors be for commissioning?
At canopy height, aspirated and shaded, in representative zones, not in dehumidifier discharge.
What is the most common commissioning problem?
Sequences that let heating, venting and dehumidification fight each other, and sensors in unrepresentative positions.
Sources
- ASHRAE Guideline 0, The Commissioning Process.
- ILAC G8:09/2019, Guidelines on decision rules and statements of conformity.
