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Numerical evaluation of the airtightness impact on airflow pattern in mechanically ventilated dwellings in France

F. Richieri, B. Moujalled, T. Salem, F.R. Carrié, 2015
simulation | airflow displacement | airtightness | ventilation system
Bibliographic info: 36th AIVC Conference " Effective ventilation in high performance buildings", Madrid, Spain, 23-24 September 2015.
Languages: English Pages (count): 11

The objective of this paper is to assess the impact of the envelope airtightness on airflow patterns for single detached dwellings depending on the ventilation system.

A numerical approach based on the energy simulation tool TRNSYS coupled to a multi-zone air-flow and contaminant transport model COMIS was used to analyze the local and global performance of four mechanical ventilation strategies in terms of energy and ventilation efficiencies. The following ventilation strategies were modelled: constant flow exhaust-only, humidity-sensitive exhaust-only with and without humidity-controlled inlets, and constant flow supply and extract. The multi-zonal approach allows studying the local disturbances in the functioning of these systems, which differs from most studies on the subject. The impacts of the location of leakages in the building envelope (facades and/or ceiling) were also investigated. Numerical results showed a significant impact of air permeability on the ventilation efficiency, with a different impact depending on the mechanical ventilation system. The wind effect exposes the building more frequently to the influence of crossing airflow, and as a result the normal distribution of fresh air from main rooms to wet rooms could be disturbed, with a risk of damaging indoor air quality. We also analysed the fresh air origin, by quantifying the amounts of airflows from leakages and inlet/supply units for each ventilation systems. Results show that in the case of humidity-sensitive ventilation systems, a specific attention should be given to the air permeability in order to maintain the desired airflow pattern from main rooms to service rooms.

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