Conclusions
Based upon the data collected in this study, we concluded that natural ventilation with supplemental cooling fans and tunnel ventilation produce similarly favorable summer conditions within freestall barns in the absence of extended periods of hot, muggy weather.
The results indicate that tunnel-ventilation would likely provide more consequential benefits during more extreme summer conditions, especially extended periods with little wind, as often occurs during hot, muggy weather. It is during these periods that tunnel ventilation can maintain high levels of air exchange through a barn, while naturally ventilated systems cannot.
This study also revealed several areas for improvement in the design of tunnel-ventilated dairy barns. Barn length needs to be considered in the design to counter the buildup of heat and moisture. Additionally, improved means of maintaining a uniform air velocity within the barn, especially in the cow space, need to be developed.
Acknowledgements
Financial support for this project was provided by the Ohio Dairy Farmers Federation and Aerotech, Inc., Mason, MI.