Comparison of Natural and Mechanical Ventilation Performance in Similar Houses

The ventilation performance in 59 terraced houses of similar construction was investigated using a passive tracer gas technique. Some thirty houses were ventilated through the original natural ventilation, while eight were equipped with an additional bathroom fan and 20 were retrofitted with a mechanical supply and exhaust ventilation system. All measurements were made simultaneously in March. The ventilation performance was computed using both single-zone and two zone approaches. Using the two-zone approach specific information about the bedroom ventilation (direct in-flow of air, purging flow rate and air exchange with the rest of the dwelling) could be obtained. A comparison between naturally and mechanically ventilated houses shows that those with mechanical ventilation on average show a considerably higher ventilation rate.