In the past few years, research efforts have been made to acquire accurate knowledge about infiltration and ventilation in multi-zone buildings. By this way, a wide variety of modelling techniques have been developed which suffer of a lack of satisfactory validations. The purpose of this work is to set up a data bank of high quality measurements which will serve to cany out an empirical validation of multi-zone air infiltration programs. Among other data, a complete set of air flow permeabilities of a well known experimental midsize building will be included to this bank. We use the guarded zone pressurization technique for the purpose of measuring this set. The system is made of two computer controlled fans which automatically pressurize the different rooms of the building. Pressures and air flows are sampled and gathered during the overall experiment which runs generally over one night. Values of the corresponding permeabilities are calculated from these data through a mean square fit. An overview of the procedure used to measure these permeabilities as well as a description of the experimental equipment developed for this purpose, is presented in this paper. The measured permeabilities and a discussion of their values, are also be given.