Due to continuously increasing energetic requirements, the building envelopes of new or refurbished buildings are highly insulated and airtight. This leads to a significantly reduced infiltration, i.e. the hygienically required outside air change rate for the building cannot be reached without a ventilation concept. In schools, with high occupancies, an insufficient indoor air quality negatively impacts the learning ability and performance of the pupils. A natural ventilation is not capable of delivering the exactly required outside air change rate, leading either to an increased energy effort or to deficits in indoor air quality.
In order to ensure the required air quality in school buildings, a mechanical ventilation, often equipped with a heat recovery, is necessary. In this context, not only the nominal outside airflow is relevant but also the local room air distribution, which depends on the design and position of the air diffusers. The local room air distribution can be indicated by the ventilation effectivity. For a constant outside airflow, the indoor air quality improves with an increased ventilation effectivity. As a result, an improved ventilation effectivity can reduce the outside airflow without affecting the indoor air quality. Therefore, substantial energetic savings can be achieved for the air distribution and air conditioning, and CO2 emissions can be reduced.
The objective of this research project is to create a planning manual to assist planners regarding an optimized air distribution in classrooms. At first, the ventilation effectivities of frequently used ventilation concepts are determined and their deficiencies are identified. For this purpose, the room airflow is investigated numerically and experimentally for a reference classroom and its impact on the ventilation effectiveness is analyzed. Based on the findings, optimization measures for the air distribution are developed, allowing to keep room conditions stable and to ensure a sufficient indoor air quality for variable occupancies. The potential energy savings through an improved ventilation effectivity are determined by using thermal-energetic annual simulations, comparing the energy expenditures of different air distribution concepts.
07/2019 – 07/2021
Deutsche Bundesstiftung Umwelt DBU (German Federal Environmental Foundation), grant number 34900/01