EFFECT OF VENTILATION ON MAXIMUM AIR TEMPERATURES IN TWELVE IDENTICAL GLASSHOUSES

The effect of ventilator opening areas between 6 and 27% of the floor area on glasshouse air temperature rise above outside air temperature was compared in an experiment in 12 identical glasshouses, with uniform cover crops in bright sunshine.
The use of roof and side ventilators was compared with using roof ventilators only (with the same total ventilation areas in the range 6–15%)and the former significantly reduced temperature rise.
Temperature rise in glasshouses, using both roof and side ventilators, was best fitted to the model log t_d= a -bV (where t_dis temperature rise and V is ventilator opening as % floor area) and accounted for 92.4% of the variation.
The model predicts a reduction of about 0.1°C (0.2°F) for each 1% increase in ventilator opening about 15%, falling to 0.05°C (0.1°F) per 1% above 27% ventilator opening.
The model could not be used to predict the temperature rise in any particular glasshouse in the block of 12 glasshouses used for the experiment as the position of the glasshouses within the block and the direction of the wind also affected the observed temperature rise.
The results are discussed with reference to subsequent experience in this block of glasshouses.

Symposium on Greenhouse Design and Environment

R.A.J. White

https://doi.org/10.17660/ActaHortic.1975.46.6