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Cascade ventilation – air exchange efficiency in living rooms without separate supply air inlets and exhaust air outlets
Authors: Gabriel Rojas, Dr. Rainer Pfluger
The principle of extended cascade ventilation is based on the idea of using the living room as a pure overflow zone without its own fresh air outlets. This approach facilitates installation and reduces the air exchange rate without reducing the quality of indoor air because fresh air is used more effectively. The floor plan has to have the right topology, however. [Sibille and Pfluger 2013] systematically investigated and assessed the suitability of a wide range of floor plans. This paper goes further to study whether the flow of air can “short circuit” between flow-through elements if they lead to a narrow hallway, such as shown in Figure 1. The strength of this short circuit was quantified based on CFD simulations and measurements of air exchange efficiency εa [Schnieders 2003]. Various parameters were adjusted to assess the impact of geometric and thermal boundary conditions on the two most common flow-through solutions in Passive House architecture (crack under bottom of door and back-ventilated frame connectors).
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Conclusions and acknowledgments
Extended cascade ventilation is an extremely efficient type of ventilation for living rooms. It reduces the work needed for installation along with operation costs and can mitigate dryness in the winter by reducing the amount of fresh air needed. The approach cannot be used, however, with air heating. Depending on the floor plan, flexibility in the way rooms are used could hamper the implementation of extended cascade ventilation. In principle, a lot of modern floor plans are excellent for implementation. If all airflow openings lead to a joint hallway and the living room does not have an integrated kitchen (with exhaust air), there is a risk of airflow short circuiting. Planning tips were worked up for such cases in this project.
A part of the FFG projects Doppelnutzen (Haus der Zukunft plus) and low_vent.com (Neue Energien 2020), this study received funding from the Austrian Ministry of Transport, Innovation, and Technology. Haus der Zukunft Plus is a research and technology program of the Austrian Ministry of Transport, Innovation, and Technology (BMVIT). It builds on the experience from Haus der Zukunft and takes account of the results of the ENERGIE 2050 strategy process. It is processed by the Austrian Research Promotion Agency along with Austria Wirtschaftsservice Gesellschaft and Österreichische Gesellschaft für Umwelt und Technik (ÖGUT) on behalf of the BMVIT. The program focuses on the Energie der Zukunft program document and covers the fields of energy and buildings.
[Hahne and Pfluger 1996] “Improvements on PASSYS test cells.” Solar energy 58(4):239–46. Retrieved August 21, 2012 .
[Schnieders 2003] “Wirkung von Position und Art der Lüftungsöffnungen auf den Schadstoffabtransport.” Pp. 85–123 in AKKP 23 (only in german language): Einfluss der Lüftungsstrategie auf die Schadstoffkonzentration und -ausbreitung im Raum, edited by Wolfgang Feist. Passivhaus Institut.
[Sibille, Rojas, and Pfluger 2013] “Planungshinweise für komfort- und kostenoptimierte Luftführungskonzepte - Erweiterte Kaskadenlüftung.”(only in german language)
Retrieved January 19, 2014
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