Unbalanced return air in commercial buildings

Research in 88 central Florida commercial buildings during the last decade has found that 26% of the air distribution systems had substantially unbalanced return air. Unbalanced return air occurs when there is a restriction to airflow between the supply discharge and the return air creating positive and negative pressure fields throughout the building. Severe consequences in commercial buildings can occur as a result of unbalanced airflows. This paper examines unbalanced return air and its consequences in three commercial buildings and explains why balancing airflow in buildings is a critical part of maintaining a healthy and energy-efficient building.