Airflow into, out of, and within buildings is a fundamental factor of building design and operation, as building airflow patterns impact occupant health and comfort, building durability, and energy consumption. This airflow is impacted by the airtightness of building elements and pressure differences created by stack effect, wind, and mechanical ventilation systems. Importantly it is the combination of these factors that will determine the resulting airflow patterns at a building.
Airflow theory is relatively well developed, and while it can be quite complex and many unknowns remain, enough is known to assist with the design of mechanical ventilation and airflow control strategies for buildings. This paper provides a summary of key aspects of the relevant theory including analysis of typical pressure differences and distributions of airtightness. The interactions of these factors and the resulting airflows that would be predicted by theory are compared with the measured results at a high-rise multi-unit residential case study building.
The case study includes measurements of airflow rates between zones using perfluorocarbon tracer methods, long-term monitoring of pressure differences, and compartment airtightness testing. Exterior conditions including wind speed and direction, temperature, and relative humidity were monitored using a weather station installed on the roof of the building to allow for evaluation of the interaction between the building and the exterior environment. Overall, this study aims to improve the general understanding of factors affecting airflows in buildings and how these factors combine to influence the performance of building mechanical ventilation systems. The results of the study allow for general recommendations with regards to the design of ventilation systems, building enclosure airtightness, and compartmentalization strategies.
This paper was presented at the 2015 BEST4 Conference.