Improvement of domestic ventilation systems.

The aim of the study was to identify methods for the renovation of ventilation systems in domestic buildings which are 3 - 8 storeys high. Three typical buildings were selected and the problems in ventilation were examined. The designers made their proposals for repairs and the research team analyzed the solutions and made improvements. The special problems compared with new buildings included less airtight building envelopes and leakages in existing ventilation ducts. An analysis was performed, using a multi-zone airflow model, for the whole year and therefore the ventilation heat loss could be found in each case. As anticipated, the airflow rate of passive stack ventilation was too high in winter and too low in summer, but the system can be improved by means of controlled air inlets and outlets. A mechanical extraction system can be improved with demand-controlled ventilation instead of time control. The installation of heat recovery system requires improved sealing of the building envelope to minimize cross ventilation. The proposed systems will be tested and followed up later in experimental buildings.