(eng): The need to exactly check and control indoor ventilation in buildings is the reason making the designers and researchers apply different simulation methods. This paper is focused on the numerical analysis of ventilation of a broiler house during the summer period with the use of computer fluid dynamics (CFD) software Fluent. Especially the summer period is critical. This paper presents the result of measurement and CFD analysis of the flow pattern, thermal state, and concentration of CO2 and NH3 inside the broiler house. Calculation respected the Czech standard. Final results show the improved arrangement of the ventilation system for summer conditions.