(eng): This paper is focused to the broiler house ventilation in summer and winter periods with respects to main welfare needs of poultry during the fattening period. Limits of ventilation configurations are given with the minimum air exchange during the beginning of fattening in winter on the one side and the maximum air exchange during the end of fattening in summer on the other side. Basic parameters of analyzed cases are set up with respect to the technical standards. Several 2D CFD (computer fluid dynamics) models for every configuration are solved using the Ansys Fluent software and discussed from different points of view with focus to the welfare of animals. The main part of work is focused onto finding the most usable configuration of inlets and outlets. Appropriate effects of longitudinal and transversal ventilation are used in different flow regimes. It is also mentioned, that mainly during the winter period, when the flow rate of the air through the interior is reduced to minimum, the concentration of pollutants and also the humidity becomes the main criterion for the ventilation system control.