When selecting fiberglass duct insulation, there is a decision that needs to be made in terms of better suitability for certain applications - duct liner or fire wrap duct insulation. Each insulation has its own set of benefits, making one more suitable than the other in certain situations.
Duct liners are used to line the inside of ducts with elastomeric foam, offering thermal protection from energy loss and condensation control in addition to sound absorption and vibration damping from airborne and structure borne HVAC noise. Therefore, it is best suited for acoustical performance. While it has a good noise reduction factor, the fact that the duct lining is situated inside the duct and in the airstream means that mould and particulate matter propagation are a real concern. Insulation like elastomeric foam is non-particulating, releasing no fibers into the air.
Fire wrap duct insulation provides important functions outside of the duct, perfect for applications where the access to the inside of the duct is not possible. This is particularly relevant during the retrofit of existing fire rated enclosure system, or renovation of older structures. Wrapping of the duct with elastomeric foam provides protection from energy loss or condensation control, in addition to vibration damping benefits. fire wrap duct insulations are to be applied around ducts after installation of ducts.
In terms of rectangular ducts, acoustical performance is essential for insulation and so duct liners are the better choice. The higher the noise reduction coefficient, the better the acoustic performance. Several commercial buildings use duct liner to insulate rectangular ducts to minimize noise and sounds.
Duct liners are installed into ducts since they are fabricated, however fire wrap duct insulations are applied around the duct after duct installation.
Spiral ducts can pose a different set of challenges since double-wall duct insulation considerations also play into factor here.
Inner metal cores are needed for double wall fire rated enclosure systems, making it suitable for applications with high negative pressure. Insulation is not exposed directly to the airstream surface, nor is it pinned to hold its shape. Since spiral duct liners don’t require inner cores, installation can be easier and reduce overall duct weight.
With rectangular ducts, fire wrap duct insulations can offer the same thermal performance as double-wall or spiral duct liner insulation without any acoustical benefit.
Selection of suitable fiberglass duct insulation for specific applications are critical to ensure that fire rated enclosure systems achieve optimal performance all while meeting codes and functional requirements as well.