VOLUME FLOW UNBALANCES AND SHORTCUTS IN DECENTRALIZED AND CENTRALIZED VENTILATION UNITS – FIELD TESTS IN RESIDENTIAL BUILDINGS

Centralized and decentralized mechanical ventilation have become state-of-the-art in modern energy-efficient residential buildings. Calculations for the energy demand of buildings are done with nominal values of the ventilation units, assuming a proper function of the devices. The used ventilation concepts may be divided into two main categories- centralized and decentralized units and both come with advantages and disadvantages in terms of energy efficiency. In Luxembourg, a comprehensive field test has been performed in order to evaluate and compare their performance in practice. It could be shown that ventilation systems often do not meet the expectations. High unbalances in volume flows, high sensitivity to pressure differences and recirculation were measured in several cases. Only a proper installation and balancing of the systems can ensure an energy efficient function.