Renovation of existing buildings, in order to reduce energy consumption, represents a big market inEurope. As the first efforts often concentrate in improving insulation and airtightness of the buildingenvelope, important insufficiencies of ventilation can appear, generating health risks for the occupants and a degradation of the frame. Taking into account the difficulties to insert ductworks in existing buildings, it can be easier to use distributed ventilation systems for room-by-room ventilation instead of centralised systems. In addition, balanced mechanical ventilation systems with heat recovery minimize the energy loss due to air renewal.Single-room balanced mechanical ventilation units with heat recovery are used in European countries. They include a air-to-air heat exchanger, two fans and filters and they take place on a wall with air inlet and outlet through the building faade. However, the performance of such devices is not well known and questions remain about their ability to ensure good ventilation of the whole room.In the research project VENTILRENOV, supported by ADEME, two representative products from themarket have been tested in laboratory as well as in an experimental full scale dwelling. Numericalmodelling has also been performed. This paper summarises the results of this project, showing theimpact of such ventilation systems on indoor air quality, energy consumption and noise.