Good acoustics and good thermal performance are required in the modern built environment. Dual wall round and oval duct with interstitial fiberglass insulation has been the gold standard for providing both at a reasonable price. In the past few years there has been concerns raised about the presence of fiberglass in the airstream creating a health hazard. This has lead to the emergence of specifications calling for a mylar barrier between the fiberglass and the perforated inner duct wall, which seriously degrades the acoustical properties of the fiberglass,or calling for the use of an elastomeric as the insulation medium, which is heavy and extremely expensive. We introduced on 2013 our E-Free
has a sound transparent polyester rayon facing between the fiberglass and the perforated inner wall, keeping fiberglass out of the airstream. Best of all it is competitively priced with the use of standard matt faced duct liner.