The Elephant in the Ceiling: What Leaky Ducts Mean for Commercial Decarbonization

What happens to a commercial building’s energy and ventilation goals when conditioned air leaks from the ductwork before reaching the spaces it is intended to serve? Duct leakage can increase HVAC energy use and compromise the delivery of air to occupied spaces, yet its role in building performance often goes unmeasured.

This session examines measurements from 25,320 commercial supply duct systems across more than 10,000 buildings. The findings challenge assumptions about duct airtightness in both existing buildings and newer construction. They also demonstrate substantial opportunities for improvement: within the measured dataset, sealing reduced leakage by a median of 89%.

Participants will explore what these findings mean for commercial building decarbonization, occupant comfort, and ventilation delivery. The discussion connects patterns across building types, climates, and construction vintages to decisions about HVAC upgrades and ongoing operations. It also examines how specifications and testing practices can leave significant leakage undetected. Attendees will leave with a practical approach to evaluating duct leakage, setting measurable performance targets, and verifying improvements as part of new construction and retrofit projects.