This study measured airflow static pressure losses through non-metallic flexible ducts in compliance with ASHRAE Standard 120-1999, Methods of Testing to Determine Flow Resistance of HVAC Air Ducts and Fittings (ASHRAE 1999). Duct sizes of 6, 8, and 10 inches were tested in a positive pressure, blow-through configuration. An “as-built” test protocol expands the test configurations specified by Standard 120. Results of the current tests extend the existing ASHRAE/ACCA data for the flexible duct, which does not include pressure loss data for flexible ducts that are compressed beyond approximately 4%. The data from this study exhibit higher pressure losses than prior ACCA or ASHRAE data. Some configurations have over ten times the pressure loss found in rigid ducts or fully stretched flexible ducts of the same diameter. The experimental results were utilized to create a set of loss prediction equations for flexible ducts that did not previously exist
