The objective of this study was to evaluate temperature/humidity conditions in freestall barns with different types of gravity ventilation and to determine the risk of heat stress in cows based on the temperature-humidity index. The study was carried out during summer months (June/July) in two free-stall barns located in north-eastern Poland. The buildings for the study were selected based on the natural ventilation and animal housing systems used. One building was equipped with supply ducts mounted over windows and a roof ridge gap, and the other had flat roof exhaust ducts and side curtain. It was found from this study that the barn having flat roof exhaust ducts and air supply from side curtain was characterized by more favourable temperature/humidity conditions and presented a lower risk of heat stress to cows compared to the barn with roof ridge and air inlets. It was also found that cows in the barn with side curtain had comfortable conditions and those in the roof ridge barn were exposed to mild and moderate stress.
