Ventilation performances of a large canarian type greenhouse equipped with insect-proof nets

This study analyses the ventilation performances of a large Canarian type greenhouse equipped with insect-proof nets on the vent openings. Air exchange rate measurements were performed in the region of Agadir, Morocco, by means of tracer gas method in a 6000 m(2) greenhouse planted with a tomato crop and equipped with insect-proof nets. A ventilation model was deduced and the simulations show that: (i) the ventilation rate increases proportionaly with the wind speed and the size of the opening; (ii) the contribution of the chimney effect in ventilation is still significant for wind velocities of about 3 m.s(-1) and still dominates up to 1.5 m.s(-1); (iii) insect-proof net induces a strong additional pressure drop through the opening, which reduces significantly the ventilation rate and generates an important greenhouse air temperature increase. The simulation model was later used to study the effects of anti-trips and anti-aphids nets on the greenhouse ventilation performances and the resulting climate.