Tunnel ventilation is a special summer ventilation system that provides a combination of the high air exchange rates and high-speed airflow over cows to help cows remove body heat during hot weather. Tunnel ventilation systems are not suitable for year-round use because they provide inadequate fresh air distribution during low air exchange winter ventilation conditions. With tunnel ventilation, the calculation for fan capacity to provide the necessary air velocity is independent of the number of cows within the barn.