Acoustical Performance of Foil-Faced Fiberglass Insulation Board

Fiberglass duct liner has been used for decades in HVAC applications for controlling noise from HVAC equipment. The fiberglass is typically coated with facings that prevent erosion of the glass fibers and more recently chemicals that inhibit mold growth. These surface treatments are porous and do not adversely impact the sound absorbing performance of the fiberglass core. However, these coatings are generally rough in texture which makes maintaining a clean surface problematic. As a result, duct liners are not permitted in many applications. Another surface treatment that is available for fiberglass insulation board is foil-scrim-kraft (FSK) facing. The foil-facing is a thin non-porous layer of foil, glass fiber scrim, and kraft paper that is bonded to the glass fiber board. This product has not generally been used for sound absorption in HVAC systems because its non-porous surface was always thought to be a poor sound absorber. Recent tests have revealed that the foil facing significantly increases the sound absorption at frequencies below 500 Hz (compared to un-faced fiberglass), and that the degradation at mid-frequencies is relatively minor. This study will present laboratory test data comparing conventional and foil-faced products, and highlight potential applications for use in commercial HVAC systems.