In the early days of insulated flexible duct, each manufacturer published their individual thermal values (R-Value) using various methods and test standards which caused confusion in the marketplace. Over time engineers, contractors and code officials required a standardized method to correctly determine & compare flex duct thermal values.
The Air Duct Council (ADC), formed by North American flexible duct manufacturers, determined early in its formation that flex duct R-Values needed to be consistent throughout the industry. The ADC with the issuance of UL and the ETL created the Thermal Performance Program for R-Value ratings in 1993 (25 years ago). This program includes testing of product, classifying each insulation thickness & density by R-Value and the follow-up testing of the product R-Values at both the insulation manufacturer and the Flexible Air Duct manufacturer. This method of testing, classifying, and follow-up testing was designed to keep the industry “honest & standardized” when publishing flex duct R-Values.
The ADC test method measures the R-Value of the insulation only. The ADC method ensures that inner core films, vapor barriers or other non-insulation components cannot be used to determine an ADC member R-Value. Most building codes today recognize & enforce the need for a standard flex duct R-Value test. Many mechanical codes include language that duct insulation R-Values be based on insulation only.
So, how do you know if a flex duct meets the R-Value required by building codes, engineers and contractors? The answer is simple. Look for the ADC Thermal Performance Seal of Certification prominently displayed on the vapor-barrier of your insulated flex duct.