Vochtgedrag schermsystemen : een zoektocht naar de oorzaak van toenemende problemen met druipend condensvocht in kassen met dubbele schermen

Het Nieuwe Telen (The New Growing) results in applying more screen layers that stay completely closed. In practise this causes problems with drip. In this research the impact of 2 screen layers and using screen gaps on the amount of drip from the screens or the greenhouse cover is investigated. Solutions to reduce the problems related to drip were proposed and tested in the greenhouse. During spring and winter 2016, measurements were performed at a tomato greenhouse with artificial lighting, blackout screen, energy screen and a Ventilationjet system. The daily amount of the condensation water that drips from the greenhouse ridge, gutter and the Ventilationjet was determined. In contrast to the general expectations, the drip does not come from the screens but from the greenhouse cover and from the Ventilationjets. Condensation occurred at the screens but this did not result in drip from these screens. Only 0.2% of the condensation against the greenhouse cover drips into the greenhouse. If this drip would be re evaporated, the energy costs for heating would increase with 0.0008 m3 gas /m2/week. Investments to reduce drip can thus only be paid back by a better crop quality and not by energy savings. The use of the inlet ventilator of the Ventilationjet system or the use of a screen gap increases the amount of condensation on a cold greenhouse cover. Drip from the greenhouse gutter was solved by applying a condensation gutter and the drip from the duct of the Ventilationjet was solved by applying a collecting tray with drain hose