A desire to reduce energy consumption associated with mechanical ventilation in conventional pig housing has led to the development of a new hybrid ventilated building design, where large adjustable openings for natural ventilation are combined with a mechanical ventilation system for under floor removal and subsequent cleaning of a limited amount of air. To ensure competitive construction costs the building was designed with large building width (>50 m) which potentially is a challenge in relation to obtain sufficient ventilation in the entire animal occupied zone. Therefore, the aim of this study was to investigate to which extend it was possible to ensure satisfactory low ambient temperature for the animals in a wide hybrid ventilated building for finisher pigs when Danish summer conditions were considered. Measurements were conducted in one 22 m long and 51 m wide section of the first hybrid ventilated building for finisher pigs, designed by the Danish company Agrifarm. Measured temperatures in six different pens were compared with outdoor temperature, room air temperature, and with estimated values for achievable pen temperatures by maximised utilization of the openings. The applied threshold for exceeding pen temperature was 24°C. The data covered a warm summer period with small finisher pigs (336 hours), and a relative chilly summer period with large finisher pigs (850 hours). The average pen temperature was above 24°C in 60% of the time for the two periods together and for that percentage of time, the average pen temperature was 26.5°C and 26.7°C, which was 3.2°C and 5.4°C higher than the outdoor temperature for the two periods, respectively. In addition, there was a statistical significant difference of 2°C and 1.7°C between highest and lowest average measured pen temperature, for small and large pigs, respectively. The potential opening area for natural ventilation was fully utilised in 348 of the 535 hours where the average pen temperature was above 24°C. Calculated in relation to all 535 hours with pen temperature above 24°C the maximum achievable decrease was only 0.2°C. In conclusion, the hybrid ventilated building was unable to keep the animals’ ambient temperature down at a sufficient level for more than half the time, during summer, and full utilisation of the natural ventilation had a negligible influence on reducing this temperature. To meet this challenge, it is suggested to investigate supplementary cooling methods.