COMPARISON OF DIFFERENT SYSTEMS FOR STATIC VENTILATION OF HEMISPHERIC PLASTIC GREENHOUSES

Three different static ventilation systems were compared to a control greenhouse with a classic lateral aeration by means of wooden pegs for spacing away the touching PE sheets.

The best results were obtained with continuous lateral ventilation, by simultaneous unrolling of the covering sheets with a crankshaft, and this in combination with ridge aeration.
Under this greenhouse the ventilation surface can reach up to 30% of the groundsurface and temperature rise was maintained within 1° C in comparison to the outdoor temperature.
The soil temperature was also the most favourable under this conditions.

The both other greenhouses, using hand winch systems for spacing away touching PE’sheets were also much better than the control greenhouse, but the efficiency of the ventilation was lesser than than for the greenhouse with continuous lateral unrolling of the covering sheets, because the created ventilation surface is only 15–20%.

The influence of the compared systems on other climate factors, such as relative humidity and enthalpy, and the ventilation rate are also discussed.

The earlier and higher yields obtained under the greenhouses with good static ventilation are allowing pay back of the systems within 2 years.

II Workshop on Greenhouse Construction and Design

Ph. Verheye, H. Verlodt

https://doi.org/10.17660/ActaHortic.1990.281.21