Richard Stowell1*, Curt Gooch#, and Scott Inglis#
*The Ohio State University Department of Food, Agricultural
and Biological Engineering
#University of Nebraska-Lincoln Biological Systems Engineering
Summary
Three pairs of naturally ventilated and tunnel-ventilated dairy barns were monitored during the summer of 2000 to compare the warm-season environments. Ambient air temperatures during midsummer were cooler than normal where the research was conducted (New York and Ohio), but both states had near-normal cooling seasons. Both ventilation systems performed well during these conditions with indoor thermal conditions closely tracking those outdoors. Tunnel ventilation provided only a slight advantage during the heat of the day in terms of moderating dry-bulb air temperature and temperature-humidity index (THI). When outdoor conditions were potentially stressful (THI greater than 70), the average temperature and THI differentials between indoors and outdoors were -0.8 F and -0.4 less, respectively, in the tunnel-ventilated barns. Average air speeds within the cow spaces were similar in both barn types during spot checks. Considerable spatial variation in airspeed existed (at least a spread of 2 mph) in all barns. Both ventilation systems produced fluctuating airspeeds at cow level on a day-to-day basis. Risk management approaches should be used to evaluate these systems. Improved designs are needed for tunnel ventilation to enable systems to maintain desired air velocities throughout the cow space and to better accommodate large barns.