Leakage in Large-Building Duct Systems: Modelling the Savings for Various Applications

Decisions about whether it is worthwhile to seal duct leakage in large buildings are based upon different needs in different applications, ranging from the need to meet diffuser/exhaust-grille flow requirements for ventilation regulations, to meeting fire-safety specifications, to maintaining zone pressurization/depressurization requirements in hospitals. However, many decisions about whether to seal duct leaks are based upon the energy and peak-electricity-demand implications of sealing that leakage. This paper discusses the varying energy and peak-demand savings mechanisms for different types of duct systems, starting with simple exhaust ventilation systems, and including Constant Air Volume systems as well as Variable Air Volume systems with different means for controlling Outdoor Air. The magnitudes of different savings mechanisms (fan power, Outdoor Air conditioning, terminal reheat, peak power reduction) will be compared for different system types, and the functional dependence on leakage level will be presented for each energy implication for each type of HVAC system.