Measured airflow through gable-roofed naturally-ventilated beef cattle barns

As the number of beef cattle being finished under roof increases, it is important to revisit ventilation design and management for both cattle comfort and emission estimation. The airflow through a barn provided by natural ventilation is affected by wind speed and direction, heat production in the barn, barn configuration and opening dimensions. The only factor that is under daily producer control is the north wall curtain management, which affects the opening dimension. Airflow data through two gable-roofed, deep pit manure storage, beef cattle barns oriented east-west were collected for >6 months for each barn. Anemometers in the north and south wall openings, the north and south eave openings, and the ridge monitored the airspeed through the external openings related to a central pen. Ambient wind speed and direction were monitored by an on-site weather station. Using the airspeed measurements and respective opening areas, the average hourly mean airflow through the various openings were regressed with respect to the ambient airspeed perpendicular and into the south wall opening of the barns. Different slopes were detected for winds from the north compared to winds from the south. The ridge was a continuous exhaust point at both sites, but the slope between airflow and ambient wind speed was greater for winds from the south compared to winds from the north.