A summary of the evaluation of an air flow and contaminant model as part of the IEA-ECBCS Annex 23 ＇Multizone Airflow Modelling＇ is presented. Evaluation, rather validation, is the goal. The most important points of the cases analyzed during this project are presented and commented from the point of view of analytical evaluation, comparison with experimental data and user sensitivity. The conclusion addresses the need for user-friendly tools and guidelines for the analysis of simulation output.