Ventilation Effectiveness of Alternating Façade-integrated Ventilation Devices in a Dwelling

Ventilation systems are designed based on the air flow volume required to ventilate the room, the same applies to façade-integrated ventilation devices operating in alternating mode, also referred to as push-pull devices. Those rather small devices represent a simple way to provide fresh air and air-to- air heat recovery for residential dwellings. The present research aims to analyse the ventilation effectiveness of push-pull devices experimentally. Hence, a tracer gas analysis is performed in a residential building. The experimental object is a storey of a residential building consisting of four rooms each equipped with one façade-integrated ventilation device. Three of these operate in alternating mode performing a regenerative heat recovery, while the fourth is an exhaust only device. The measurements are carried out during summer and winter to investigate the influence of the varying climate boundary conditions. In order to evaluate the ventilation effectiveness, the age of air is determined based on the concentration decay method applying CO2 as a tracer gas. For the evaluation the air exchange efficiency εa in the breathing zone at 1.7 m height was applied. As a conclusion it was found that push-pull devices can provide a mixed ventilation characteristic although there are trends for a vulnerability to pressure and temperature differences between the in- and outdoor surroundings, which lead to ventilation short circuits.