This paper presents influence of direction and energy of wind on forming of ventilation air velocity in chosen area of the free stall barn during summer. Based on analysis of obtained measurement results characteristics of the wind speed in summer was made. Variability of the ventilation air velocity with take into account of perpendicular and parallel wind direction was determined. Noticed differentiation of air velocity depending on measurement place - central barn area was less ventilated than area close to wall. Proposals setting out the reasons for the abnormal air flow were formulated. In order to increased ventilation air velocity in central part of the barn recommended use to air mixers. Attention was drawn to need of continue studies of different barn types relative to building construction solution and its localization.     ...