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The implementation of decentralised ventilation units is growing, especially in the residential retrofit. These systems are typically simple to install on site (usually in the external façade with no additional ductwork) and allow room-by-room control strategies. Until now, decentralised systems are evaluated by applying the same methodologies as for centralised ventilation systems, even though different boundary conditions apply. Some differences are for example:
- thermal bridges through the casing of the ventilation device are more important to consider
- most of the decentralised ventilation systems operate by alternating supply and exhaust airflow through the same flow channel
- they usually need almost no ductwork
Furthermore, the existing mandatory evaluation methodologies (based on the Energy Performance of Buildings Directive, EPBD) are focused on the evaluation of the energy performance. This evaluation of the energy performance is not combined with other aspects, such as e.g. the influence of the ventilation unit on the indoor air quality (CO2, VOC, among others), the indoor air age distribution, the temperature or the moisture distribution in a room, etc. Within the following paper, a new evaluation method is going to be introduced. The methodology is modular, rating the performance of decentralised ventilation systems related to a variety of aspects such as their energy efficiency, the resulting indoor air quality for a residential use, hygrothermal comfort, etc. The new evaluation method, which is theoretically introduced here, will later be implemented in a climate-chamber test-facility to evaluate and assess decentralised ventilation systems.