Duct insulation material and method of using

[0001] This application claims the benefit of U.S. Provisional Application No. 60/939,391, filed May 22, 2007, the contents of which are incorporated herein by reference.

[0002] The present invention generally relates to materials suitable for use in heating, ventilating, and air-conditioning (HVAC) ducts. More particularly, the invention relates to an insulation material that can be used as an external duct wrap or an internal duct liner, and is capable of providing noise suppression, thermal protection and, if used as an internal duct liner, does not expose the airstream within the duct to harmful fibers.

[0003] With the advance in HVAC duct design, much larger ducts are required to move air from both hot and cold air sources. The movement of air through a large duct system can generate a significant level of noise, as well as a need for more effective thermal protection as compared to smaller ducts. For this reason, external duct wraps that surround the duct exterior and internal duct liners that line the interior surfaces of the duct have been proposed. Flexible wraps and liners containing fibrous insulation materials (e.g., fiberglass) have typically been the material of choice for meeting these challenges, though if used as a duct liner there can be a concern for harmful fibers becoming entrained in the airstream, especially in hospitals, nursing homes, and schools. Another approach that has been proposed is to use rigid or semirigid insulation board materials. While generally avoiding the risk of loose fibers, rigid board materials must typically be kerfed to enable the material to be shaped and sized for the particular duct.

[0004] The present invention provides a flexible insulation material and a method for using such a insulation material with an HVAC duct to provide noise suppression and thermal protection. The insulation material can be used as an external duct wrap or an internal duct liner, and in the latter case does not expose the airstream within the duct to harmful fibers.

[0005] The flexible insulation material includes a lofted substrate and a facer sheet laminated to the substrate. The substrate contains nonwoven lofted fibers, and the flexible insulation material is attached to the duct such that a first surface of the substrate faces a wall surface of the duct. The facer sheet is laminated to a second surface of the substrate opposite the first surface thereof. The facer sheet includes a polymeric film, a metallization layer on the polymeric film, and optionally a corrosion-resistant protective coating on the metallization layer. The flexible insulation material is secured to the duct and provides thermal insulation and sound attenuation properties, and the nonwoven lofted fibers of the substrate are contained between the facer sheet and the wall surface of the duct.

[0006] The method of the invention entails securing the flexible insulation material described above to the duct described above as an external duct wrap or an internal duct liner to provide thermal insulation and sound attenuation properties.

[0007] A significant advantage of this invention is that the flexible insulation material can be installed within a duct as an internal duct liner, or installed outside the duct as an external duct wrap. If installed as an internal duct liner, the nonwoven lofted fibers of the substrate are contained between the facer sheet and the wall surface of the duct such that the nonwoven lofted fibers are prevented from being released from the flexible insulation material into the airstream within the duct. Furthermore, the polymer film and/or the metallization layer provide a very smooth surface that significantly reduces the generation of sound produced by the airstream moving through the duct. On the other hand, if the flexible insulation material is installed outside the duct as an external duct wrap, the metallization layer can be deposited to have a low emissivity that, preferably when protected by the protective coating, inhibits heat transfer between the duct and its surrounding environment.

[0008] Other objects and advantages of this invention will be better appreciated from the following detailed description.

[0012] FIG. 1 shows flexible insulation materials 40 installed as both an internal duct liner within an airflow passage of an HVAC duct 10, and an external duct wrap surrounding the duct 10. Such a duct 10 is typically formed of sheet metal, though other materials are foreseeable. Furthermore, though the duct 10 is shown as having a square cross-section, other cross-sectional shapes are foreseeable. Because of their flexibility, the insulation materials 40 can be secured to internal and external walls of the duct 10 with an adhesive tape 50 of any suitable type, though other fastening methods and materials are also within the scope of the invention. The insulation material 40 used as the internal duct liner preferably uniformly contacts the internal wall surfaces of the duct 10, whereas the insulation material 40 used as the external duct wrap is represented as being spaced apart from the duct 10, for example, by about one to three centimeters, with spacers 60, creating a substantially continuous air gap between the insulation material 40 and the outer surface of the duct 10. This air gap, in combination with the construction of the insulation material 40 described below, is desirable to enable the duct wrap to meet thermal values of code requirements for duct wrap materials.

[0013] According to a preferred aspect of the invention, the insulation materials 40 can be, though are not required to be, identical. For convenience, the insulation material 40 used as the internal duct liner of FIG. 1 is shown and described with reference to FIGS. 2 and 3, though with the understanding that such description can and preferably does apply to the insulation material 40 employed as the external duct wrap, with potential differences noted when appropriate. As represented in FIG. 2, the insulation material 40 comprises a facer sheet 20 laminated to a substrate 30. The substrate 30 is preferably made up of nonwoven fibers lofted to a specific density to achieve the thermal R-value required for a given application. A particular example is a nonwoven lofted polyester (polyethylene terephthalate) fiber material commercially available from various manufacturing sources, including Western Nonwovens, Inc. The material produced by Western Nonwovens is a blend of recycled polyester staple fibers that contains about 10% of 0.95 Denier polyester fibers, about 30% of low melt polyester fibers, about 30% of 3 Denier polyester fibers, and about 30% of 6 Denier polyester fibers. The preferred example has a basis weight of about 1.5±10% ounces per square foot (about 4 g/m²). Different proportions of other types of fibers are also foreseeable, for example, cotton fibers produced from shredded denim and commonly known as “shoddy” can also be used as the nonwoven lofted fiber material for the substrate 30. Suitable thicknesses for the substrate 30 will vary depending on the particular application and thermal performance required of the insulation material 40, though a thickness of about one inch (about 25 mm) or more is generally believed to be preferred for large HVAC ducts.

[0014] The facer sheet 20 is formed to have at least one metallized film, optionally protected with a corrosion-resistant protective coating. These layers of the facer sheet 20 are represented in FIG. 3 as a polymeric film 22, a metallization layer 24 on the film 22, and a protective coating 26. The material for the film 22 is preferably polyester (polyethylene terephthalate) or another suitable facing material capable of meeting the conditions of code compliance for the specific application. Suitable nominal thicknesses for the film 22, metallization layer 24, and protective coating 26 are believed to be about 42 to about 48 gauge, though such thicknesses can vary. The protective coating 26 is useful to inhibit corrosion of the metallization layer 24, which is particularly desirable if the metallization layer 24 defines the outer exposed surface of the insulation material 40 as represented in FIG. 3. For example, as an external duct wrap, the insulation material 40 exhibits improved thermal performance if its outer surface reflects thermal radiation from the surrounding environment as a result of being defined by the metallization layer 24. Still further improvements can be achieved if the inner surface of the material 40 (facing the duct 10) is defined by an additional facer sheet (not shown) with a metallization layer as described for the facer sheet 20, and this additional metallization layer is spaced apart from the duct 10 as shown in FIG. 1 to enable thermal radiation emitted from the duct 10 to be reflected back to the duct 10. Finally, the thermal performance of a duct wrap formed of such an insulation material 40 is promoted if one or both metallization layers 24 exhibit low emissivity (0.05 or less), and the protective coating 26 is present to inhibit corrosion of each layer 24 to maintain the high reflectance of the facer sheet 20. A commercial example of a facer sheet 20 having the construction shown in FIG. 3 is manufactured by the Dunmore Corporation (Bristol Pa., USA) and identified as product number MO16531 200 DC PE/AL/CRC. The preferred metallization layer 24 is aluminum and the protective coating 26 is believed to be a polyester or acrylic resin-based lacquer that may contain ultraviolet inhibitors. Such lacquers are believed to be disclosed in U.S. Pat. No. 4,353,766 to Dani, the contents of which are incorporated herein by reference. Other combinations of metallization and protective coatings are also within the scope of the invention if capable of providing a low emissivity of 0.05 or less desired for the facer sheet 20, and inhibiting any significant degradation of the emissivity over time after the insulation material 40 is installed on the duct 10.

[0015] When the insulation material 40 is installed on the interior and/or exterior wall surfaces of the duct 10, the nonwoven lofted fiber substrate 30 provides both excellent sound attenuation and thermal resistance properties that meet the requirements of a variety of HVAC duct applications. Furthermore, when the insulation material 40 is used as an internal HVAC duct liner, the facer sheet 20 provides a very smooth surface to reduce air resistance and provide a cleanable surface. If the insulation material 40 is used as external HVAC duct wrap and/or as an exterior sound and thermal blanket, the facer sheet 20 provides a vapor barrier and, when facing an air space or gap as discussed above, provides additional thermal resistance. Other potential applications include thermal and sound barriers for automotive applications. By varying the thickness of the nonwoven lofted fibers of the substrate 30 with the low emissivity metallized film facer sheet 20, the insulation material 40 can also be used as thermal insulation in residential and commercial constructions, particular in environments in which chemically sensitive people are present.

[0016] Any lamination process can be used to laminate the metallized facer sheet 20 to the nonwoven lofted fiber substrate 30. Manufacturing the insulation material 40 generally entails manufacturing the substrate 30 to an appropriate thickness and density to yield the desired thermal and sound transmission properties for the intended application, and then laminating the metallized facer sheet 20 to at least one surface of the substrate 30 using a suitable adhesive (not shown) to achieve properties that will meet industry required testing standards. Suitable adhesives for this purpose include water-based and solvent-based adhesives that contain a fire retardant or otherwise do not contribute to flame spread or smoke in accordance with the fire rating system of ASTM E 84 entitled “Test Method for Surface Burning Characteristics,” to achieve a Class A fire rating per this standard.

[0017] While the invention has been described in terms of a preferred embodiment, it is apparent that other forms could be adopted by one skilled in the art. For example, the physical configuration of the insulation material 40 and its layers could differ from that shown, and materials and processes other than those noted could be used. Therefore, the scope of the invention is to be limited only by the following claims.