Vapor Pressure Deficit as an Indicator of Condensation in a Greenhouse with Natural Ventilation Using Numerical Simulation Techniques

The relationship between Vapor Pressure Deficit (VPD) and condensation in a naturally ventilated Gothic greenhouse in northeastern Mexico was analyzed using numerical simulation techniques. This study was carried out in 3D in a steady state, considering the presence of crops. The model was validated with experimental data on temperature and relative humidity. Custom Field Functions (CFFs) were implemented to calculate VPD and dew point temperature (Tdp). The conditions that cause condensation inside the greenhouse were analyzed by evaluating days with and without the presence of condensation, with 100 and 50% window opening configurations, and the relationship between condensation and VPD levels was established as an indicator of this phenomenon. The simulation results showed that condensation conditions can be prevented by opening the ventilation at its maximum capacity in a timely manner. In the simulation with a 50% opening, VPD values of zero were reached and coincided with zero and negative values in the subtraction of ambient temperature and dew point temperature. However, when opening the windows to 100%, the VPD maintained values between 0.15 and 0.25, and the dew point temperature remained below ambient temperature by up to 2 °C. It is concluded that the VPD can indicate the risk or presence of condensation inside the greenhouse.