In order to get a useful tool for global and long-term assessment of the performances of ventilation systems, the experimental house MARIA and ventilation systems are modeled in MATLAB/Simulink environment. This paper quickly describes the multi-zone airflow and pollutant transfer model and deals with the validation by experimental means. Firstly, tracer gas methods are used to evaluate pollutant transfer within the real house. Then, numerical investigations are performed with the developed airflow tool by using some measured parameters as input data. Comparisons between the numerical and experimental results show that the evolution of the concentrations is adequately modeled. However, concentrations from the model were high enough. Then, a parametric study is carried out in order to determine the influential factors and better represent the experimental house by an airflow model; it finally appears that the internal airflow connections and the envelope air leakage should be better known.