A computer model for optimisation of the internal climate in animal housing design

The climate control is essential for animal production, but the building parameters concerning the internal climate are not always reliable if calculated in a conventional stationary way. As an aid for design, a software tool has been developed to simulate the transitory climatic condition inside closed buildings such dairy cow barns or pig houses. Main program inputs are: wall, roof and floor material layers (included insulating air interspace), building orientation, openings specifications (size and position), overall geometrical specifications, kind of breeding, local latitude and longitude. Furthermore it is possible to consider the wind speed and direction. The program output concerns the heat balance (sensible and latent) and the calculation of the temperature humidity index over the day. This simulation takes into account the daily sun path, the eventual roof shadowing on the vertical walls, and the water evaporation from the floor. The heat transmission through the walls is calculated by the finite difference method. The Natural ventilation has been evaluated numerically calculating firstly the neutral plane , and then calculating the air flow at each time-step using the pressure coefficients method. Internal air temperature and humidity have to be intended as mean values. The model has been validated (and implemented) through a comparison between the calculated internal air temperature and humidity and the real values measured in a house for fattening pigs. The complete simulation of the internal climate permits to optimise the thermal performance of the buildings during the whole year, which means to reach the best compromise (in terms of building design) between the opposite requirements of the cold winter and hot summer climatic conditions.