Duct leakage testing in Portugal, a consulting engineer view and experience

Duct leakage airflow in existing ductwork can reach values of over 20% of the design air handling unit (AHU) airflow, undermining efficiency and effectiveness of HVAC systems. We have measured, in an existing building where ductwork was installed 20 years before, with no special care on duct leakage and tight building construction schedules, operational duct leakage rates between 10% and 40% of the AHUs airflows.