Vertical temperature and humidity gradients in a naturally ventilated greenhouse

Experiments were conducted in a full-scale, commercial greenhouse, to study the vertical distributions of temperature and humidity ratio under closed and naturally ventilated conditions. A comparison was made between ventilat ion by continuous roof openings only and ventilation by opening both roof a nd side windows. Two cases were considered for each of the ventilation mode s: (i) the plants in the greenhouse were mature and big, and (ii) the plant s were young and small. With mature plants, the gradients of temperature an d humidity ratio before opening the ventilation windows were considerable a nd they remained so after the windows were opened (either roof only or both roof and side windows). Smaller gradients were observed with only roof ven tilation, than with ventilation via roof and side openings. With young, sma ll plants the gradients were much smaller than with mature plants and they could be assumed negligible for either ventilation mode. (C) 2001 Silsoe Re search Institute.