The CEN TC 156 / WG2 (ventilation for residential buildings) has prepared a new European draft for the test method of Heat Recovery Units (prEN 13141-7). This method should ensure a common way of testing these units all over Europe. In order to determine if the draft procedure is sufficient enough, both VTT and CETIAT has proceeded to some tests according to the new European standard on the same unit. Results on this first intercomparison give interesting data on the test method applied. These tests include a parametric study in order to highlight the influence of the following parameters: pressure, flow balance, temperature conditions, flow leakages, humidity on the temperature ratio (efficiency).