Pigs are subjected to intensive environment control and management in order to achieve higher productivity. This is due to their sensitivity to climatic variation, which strongly affects their growth. This paper reports the design optimization of a forced ventilation piggery using computational fluid dynamics. This numerical investigation determined the effect of varying the number of ventilation openings and their location on the air flow pattern, speed, temperature, power needed, ability to remove heat and residence time. The effect of varying the ventilation rate in a range (0.05 – 0.8 m 3/s), and ambient temperatures of 5°C and 32°C was also investigated. The modeled piggery has dimensions 40 m × 15 m × 2.6 m, with central walkway and gable roof with the apex at 3.9 m and is a common design in Australia. A steady-state two-dimensional numerical model based on the integral volume method, including the effects of buoyancy and heat generated by the pigs, was solved using the computational fluid dynamics software “Fluent.” Four designs were investigated and an optimum design, which facilitates better ventilation of the majority of the room, has been identified. In summer, an inlet velocity has been recommended which achieves optimum environment inside the piggery meeting the pigs’ thermal comfort criteria with minimum power usage. During winter it became obvious that heating has to be used in all designs to be able to meet the pigs’ thermal comfort criteria.