1. Natural ventilation The large glass greenhouses relies on natural ventilation for most of the time to regulate the indoor environment. The structure of a large-scale production Transparent Glass Greenhouse is generally a double-slope multi-span greenhouse, and the ventilation form is to provide ventilation windows on the side walls and the ridge. The total ventilation area is not less than 15% of the greenhouse area, preferably more than 30%. When the roof louver is opened, the sash is preferably inclined upwards above the horizontal plane, and when it is fully opened, it forms a 100-degree angle with the horizontal plane, so that a good ventilation effect can be obtained. The ventilation of natural ventilation is related to the wind speed, wind direction, ventilation window position, ventilation window area and temperature difference inside and outside the greenhouse. When the total area of the ventilating window is 27% of the indoor area, if only the ridge is ventilated, even if the outdoor wind speed reaches 10 km/h, the ideal ventilation rate of 0. 75 times per minute is not achieved; when the roof ventilating window and side wall When the ventilating window is fully open, the ventilation rate can reach 0.68 times/min in the case of almost no wind, which is close to the normal recommended 0.75 times/min air exchange rate.
2. Forced ventilation glass greenhouses rely on natural ventilation to regulate the environment most of the time. However, when the summer temperature is high, especially in the hot weather where the outdoor temperature exceeds 33 °C, forced ventilation is used when natural ventilation is difficult to meet the greenhouse cooling requirements. And with other measures to cool down is a common means of production. Forced ventilation is the use of a fan to convert electrical energy or other mechanical energy into wind energy, forcing air flow for greenhouse ventilation and cooling. The theoretical cooling limit for forced ventilation is that the indoor air temperature is equal to the outdoor air temperature. Because, at this time, the temperature difference between the inside and outside of the greenhouse is zero, the ventilation is infinite, which is impossible in practical application. Due to the mechanical and plant physiological reasons, the ventilation intensity of the general greenhouse is 0.75 times per minute to ~1. 5 times, able to control the temperature difference inside and outside the greenhouse within 5 °C.