Thermal environmental performance of a dairy barn cross-ventilated in warm weather and naturally ventilated in cool weather

Dry-bulb and dew-point temperatures were monitored at four locations in a unique freestall dairy barn that was cross-ventilated in warm to hot weather and naturally ventilated in cool to cold weather. The 10-row barn had four pens, sprinklers along two feed lines and housed up to 800 lactating cows. The barn was 70 m wide, 112 m long, had 4.4 m sidewalls, four adjustable baffles, a 0.5:12 roof slope and an open ridge with a butterfly baffle. The south wall had 52 belt-driven, 1.4 m diameter exhaust fans and an adjustable curtain opening above the fans. The north wall had three adjustable curtains. During three hot days, when the barn was cross-ventilated, the average dry-bulb temperature increase from baffle 1 to baffle 4 was 0.3ºC; the maximum was 1.4ºC. The average baffle 3 temperature humidity index (THI) value was 2.8 units higher than ambient during three hot days. THI values indicated 10 to 32 days of heat stress depending on criteria used. Milk production declines of 2% or more indicated six heat stress events commonly 1 to 2 days after the THI indicated heat stress days. In warm and hot weather, dry-bulb temperature and THI changes depended on whether a pen was empty because cows were being milked and whether feedline sprinklers were used. During two mild weather days when the barn was naturally ventilated, dry-bulb temperatures in the barn were on average 5ºC warmer than ambient, ranging from 0.6ºC to 11ºC warmer. In cold weather, when ambient temperatures were between -25ºC and -28ºC and the barn was naturally ventilated, pivot table results indicated that average barn temperatures were 25ºC warmer than ambient. During two cold-weather days when the barn was naturally ventilated, the barn was on average 24ºC warmer than ambient, but ranged from 20ºC to 28ºC warmer. Overall the barn performed well.