This paper discusses in detail the behavior of a nonduct exhaust-only ventilation system in an experimental house for which the outflow-inflow paths (i.e., simple openings such as vents and cracks in the envelope, undercuts in inner doors) are modeled by very simple cylinders. The test equipment presented here is composed of a full-scale house model located in an artificial climate chamber where the influence of wind is minimized as much as possible, thereby offering accurately controlled internal-external temperature differences. A series of experiments with this equipment has made it possible to evaluate the effects of various parameters under the same conditions (airtightness of house, size of undercuts in inner doors, internal-external temperature difference), which was impossible in the on-site measurements.

From experimental results, it has been demonstrated that in an extremely airtight house, stable ventilation almost unaffected by an internal-external temperature difference can be achieved by a nonduct exhaust-only ventilation system with a single exhaust fan continually operated, if suitable door undercuts are provided. It has also been verified that at a certain low level of airtightness, the system does not work efficiently, and that in a house where the area of cracks in the envelope is too large, sufficient negative pressure cannot be generated by a single fan. Such a house is, therefore, unsuitable for being ventilated by the exhaust-only technique.

Units: SI