Performance of natural ventilation in dwellings. A longitudinal computational simulation study.

The paper presents the results of a simulation study performed by means of the COMIS multizone infiltration and ventilation model. The simulations were carried out for a two-storey single-family passive-stack-ventilated house in a cold climate (Stockholm, Sweden). Main conclusions of the study include the following: it is possible - during at least 75 % of the heating season - to achieve a ventilation rate in the whole house of at least 0.5 ach or approx. 30 l/s only if the house has a leakage rate above approx. 10 m³/m²,h@50 Pa or has purpose-provided supply air devices in the facade with a total area (far) greater than 400 cm²; that the flow rates in the vertical shafts from kitchen, WC and bathroom are small but quite stable, in the range of appr. 3-4 l/s each; that all bedrooms (on the first floor) are underventilated as far as outdoor air is concerned; and that the living room (on the ground floor) is the only room in the house with - in most cases - adequate ventilation. Possibly, but this was not proven, the performance of the passive stack ventilation could be improved, especially in the bedrooms, if the air supply devices in the facade were to be placed lower than in the simulations (2.1 m above floor level) andfor each bedroom was equipped with an individual exhaust shaft combined with a more or less airtight door. In order to increase the shaft flows it would, of course, also be possible to increase the height of the shafts above roof level andor use a cowl of a special design. The work was undertaken as part of the IEA Annex 27 project.