This article presents the results of the experimental study performed to obtain the leakage or infiltrations of air into a conditioned enclosure. This information is very important considering that could be useful to calculate the thermal load of the building and/or refrigeration systems in order to estimate the influence of this parameter on the conditioned space thermal balance. The study is performed on a test-bench specially designed to simulates the thermal behavior of an office, with a single wall exposed to outside climatic conditions where a window is located, the variables involved in the thermal balance of the window are monitored each minute, during one year.