GrowSave, the Horticulture Development Company's energy-saving project, joined forces with the industry's tomato working party to share the latest thinking on low-energy greenhouse climate management from Rene Beerkens of Hoogendoorn Growth Management.
Beerkens advised growers to start monitoring absolute humidity levels - the water content of air - in their glasshouses. It costs nothing to monitor and can be done on all makes of climate-control computer. Beerkens advised growers to achieve constant and stable absolute humidity levels during the night.
"If absolute humidity is increasing then moisture levels are also increasing and there is a greater likelihood of condensation. If absolute humidity is decreasing, you are using too much energy."
Beerkens also explained how condensation can usually be attributed to an uneven greenhouse climate. If temperatures vary between the position of the temperature and humidity sensor and other areas in the glasshouse, growers will get poor humidity control and waste energy.
Cold spots, particularly at the sides of the glasshouse or under gaps in thermal screens, are the usual culprits. Beerkens outlined ways to combat these problems, including installing apex seals in the ridge above the thermal screen, using side screens and moving to ventilation above closed thermal screens.