Ventilation is necessary to provide good indoor air quality to occupants in buildings but can be a major energy consumer. Results from two experimental studies carried in several dwellings and in office buildings show that the use of presence detection (infrared sensor) for controlling ventilation has a potential for substantial reductions in the heating energy consumption. A simulation study of the impact of infrared spectroscopy (IR) controlled ventilation on the yearly heating energy consumption was performed and it showed that reductions from 27% to 47% can he obtained in well insulated office buildings.