Patent Publication Number: US-7222645-B2

Title: Duct insulation having condensate wicking

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation-in-part of U.S. patent application Ser. No. 10/448,757, filed May 30, 2003, now U.S. Pat. No. 6,814,105 the contents of which are hereby incorporated by reference in its entirety. 

   TECHNICAL FIELD 
   This invention relates generally to a method and apparatus for insulating ducts for use in heating, ventilating, and air conditioning applications. More particularly, this invention pertains to an insulating process and apparatus involving duct insulation with condensate wicking having a pendently suspended wicking media located inside of the air duct. 
   BACKGROUND OF THE INVENTION 
   Generally, heating, ventilating, and air conditioning (HVAC) systems include such equipment as air handling units and air ducts. Typically, HVAC systems are provided with duct insulation for thermal and/or acoustic purposes. Conventional duct insulation used in HVAC systems typically includes a facing layer adhered to an insulation layer. The duct insulation is installed with the facing layer of the duct insulation positioned away from the air duct. During periods of high relative humidity, water vapor may condense on the air duct. The facing layer is typically non-porous such that the facing surface acts as a barrier between the insulation body and the external environment. As such, the duct insulation is not conducive to the escape or dissipation of the condensed water vapor on or within the insulation layer. Even when the duct insulation is unfaced the condensed water vapor may remain on the duct surface or trapped in the insulation layer. As a result, damage may be caused by the condensed water vapor to the air duct, the insulation layer, or the facing layer. 
   SUMMARY OF THE INVENTION 
   To solve the problems outlined above, the present invention provides an insulated duct-wrap insulating product for an air duct that incorporates a wicking media to transport condensed water on the duct surface to be evaporated into the atmosphere. A wicking fabric, or fibrous media, incorporated as part of the insulating duct wrap is in contact with the metal air duct surface. A portion of the wicking fabric extends into the interior of the air duct, typically through joints in the duct system. The extension of wicking fabric is conveniently inserted into the duct at the joints of the metal ducting system when the system is installed. When water vapor condenses on the air duct surface it is transported by the wicking fabric and evaporated from the wick surface within the air stream being transported by the ducting system. 
   The use of conditioned air within the ducting system for evaporating water that is transported from the surface of the duct is an efficient method for providing evaporation within the air stream without exiting or creating flaws in the vapor retarding jacket. The ducting system provides the shortest path for transporting condensed water from the wicking surface without breaking the continuous barrier to water vapor supplied by the insulation. The water vapor that is evaporated from the wicking fabric enters the air stream and is circulated within the living space or transported directed to the return air plenum where it can be removed by the condensing coil of the air-handling unit. 
   Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic cross-sectional view of a portion of an insulated duct assembly in accordance with this invention. 
       FIG. 2  is a schematic cross-sectional view of a portion of the insulated duct assembly in accordance with another embodiment of this invention. 
       FIG. 3  is a schematic partially cut away view in perspective of an insulated duet assembly in accordance with this invention. 
       FIG. 4  is a schematic cross-sectional view of a portion of an insulated duct assembly combining the embodiments of  FIGS. 1 and 2 . 
       FIG. 5  is a schematic cross-sectional view of a portion of the insulated duct assembly in accordance with another embodiment of this invention. 
       FIG. 6  is a schematic partially cut away view in perspective of an insulated duct assembly in accordance with this invention. 
       FIG. 7  is a schematic view in perspective of an insulated duct assembly in accordance with this invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As shown in  FIG. 1 , a laminated insulation blanket, indicated at  20 , surrounds is elongated duct  12 . Elongated duct  12  is a typical sheet metal duct such as an air conditioning duct. However it will be appreciated that the elongated duct  12  may be any duct suitable for transporting air through a ventilation system. The laminated insulation blanket  20  has an insulation material layer  25  composed of compressible fiberglass insulation. While the insulation material layer  25  is described as being composed of compressible fiberglass insulation, it will be appreciated that the insulation material layer  25  can be composed of any suitable material for insulating the elongated duct  12 . For example, other mineral fibers could be used including, but not limited to, elastomeric foam, foam glass, rock wool fibers, slag fibers, and basalt fibers, and organic fibers including but not limited to polypropylene, polyester and other polymeric fibers. 
   The laminated insulation blanket  20  has an inner wicking layer  15 , which is at least partially in contact with the elongated duct  12 , so that when water vapor condenses on the elongated duct  15 , the condensed water vapor is drawn into the inner wicking layer  15 . The inner wicking layer  15  has an affinity for liquids, and the layer transports liquid water away from the surface of the duct. Also, condensed water within the inner wicking layer will migrate from areas of higher concentration of water to areas of lower concentration, i.e., capillary action. Although the inner wicking layer  15  is shown as separate from the insulation material layer  25 , it will be appreciated that the inner wicking layer  15  may be formed integrally within the insulation material layer  25 . 
   Therefore, as an alternative to a laminated insulation blanket  20 , a non-laminated insulation blanket having wicking material integrated into the interior side of the layer  15  may alternately be used as the insulation for the elongated duct  12 . The inner wicking layer  15  is preferably composed of a non-woven wick material, such as, for example, a non-woven nylon fabric. It will be appreciated, however, that the inner wicking layer  15  may be composed of any material suitable for drawing and transporting the condensed water vapor such as a non-woven material that can be formed from a polymer or natural fiber such as rayon. Rayon fibers are striated, or include channels, along the length of the fiber, which provide capillary channels in individual fibers so the wick does not rely upon capillary action formed in the channel between two adjacent fibers. Rayon fibers are striated by their manufacture; it is possible to form striations in other polymers for example by forming trilobal fibers of any polymer material. Any polymer fiber exhibiting a striated structure would provide improved wicking properties. 
   A wicking layer section  40  of the wicking layer  15  extends into the interior of the air duct  12 , typically through a joint  18  of the elongated duct  12 . Although the joint  18  is depicted as being in the center of the elongated duct, the wicking layer  15  may extend through joints located in the corners, sides or bottom of the elongated duct. Typically, the joints in the duct system are zippered joints commonly known in the art. The inner wicking layer  15  may extend through said air duct in intervals of about four feet. 
   Although a rectangular air duct is shown, the duct may be any standard air duct of any shape, i.e., circular. Section  40  of the wicking layer  15  is inserted between the joints so that the wicking layer section  40  is inserted in the interior of the duct  12  so that it is in contact with the air stream (not shown) flowing through the air duct  12 .  FIG. 1  shows wicking layer section  40  as being suspended from the top of the duct. The wicking layer section  40  may, alternatively, be inserted in seams located in the corners, sides or bottom of the air duct  12 . When water vapor condenses on the air duct surface it is transported by wicking layer  40  to the wicking layer section  40  and evaporated from wicking layer section  40  within the air stream flowing through the ducting system. 
   The insulation blankets described above may be any size and is fitted around conventional air ducts using standard installation practices. The insulation blankets of the present invention are typically installed around the air duct by wrapping the blanket around the air duct so that the insulation blanket is not excessively compressed at duct corners. The facing of the insulation blanket has an overlapping flange (typically 1 inch) which overlaps the adjacent wrapped section and is sealed with pressure-sensitive tape matching the facing (either plain foil or FRK backing stock) or glass fabric and mastic. 
   As shown in  FIG. 1 , the insulation blanket is installed by wrapping the insulation blanket  20  around the elongated duct  15 . A portion of the inner wicking layer  40  is inserted into the air duct, i.e., typically through a joint. A first edge  45  of the insulation blanket  20  is secured to a second edge  47  of the insulation blanket by tape  43  or other adhesive means at seam  41 . 
   The wicking layer section may also be inserted into a joint between adjoining air ducts.  FIG. 3  illustrates a first air duct  44  and second air duct  61  encased by insulation blanket  50 . Wicking layer section  48  is inserted into the interior of the air duct via joint  46 . For illustration purposes, the insulation blanket does not encase air duct  44 . As shown in  FIG. 3 , the wicking layer section  48  extends across the interior upper portion of the duct. Alternatively, the wicking layer section  48  may be inserted into the duct through the sides or through bottom of the duct (not shown). 
   As shown in  FIG. 2 , laminated insulation blanket, indicated at  22 , surrounds elongated duct  14 . In this embodiment of the present invention, an outer wicking portion  25  of said inner wicking layer extends through said insulation blanket  22  through a slit (not shown) to the exterior surface  36  of said insulation blanket at the bottom portion  17  of the insulation blanket  22 . The outer wicking portion  25  is then affixed to the exterior surface  36  using a conventional adhesive or tape. 
   As above, the laminated insulation blanket  22  in  FIG. 2 , has an inner wicking layer  16 , which is at least partially in contact with the elongated duct  16 . When water vapor condenses on the elongated duct  14 , the condensed water vapor is drawn into the inner wicking layer  16 . When water (not shown) condenses on the elongated duct  14 , gravity, in combination with capillary action, transports the water to the outer wicking portion  25  where the water is then evaporated. 
   In an alternative embodiment as shown in  FIG. 4 , the wicking layer section located directly in the air stream is combined with the outer wicking portion, which extends to the outside air, to provide additional condensate wicking properties.  FIG. 4  illustrates insulated duct assembly  60 . Insulation blanket  64  having wicking layer  66  is wrapped around air duct  62 . Wicking portion  68  extends through the air duct  62  into the air stream inside of the duct. A second wicking portion  70  extends through the insulation blanket  64  to the exterior surface of the insulation blanket and is affixed to the outer surface  67  of the insulation blanket by means of an adhesive or tape. 
     FIG. 5  illustrates an alternative embodiment of the present invention. A laminated insulation blanket, indicated at  72 , surrounds elongated duct  78 . The laminated insulation blanket  72  is made of fibrous insulation material  74  and has an inner wicking layer  76 , which is at least partially in contact with the elongated duct. Wicking layer sections  86 ,  88  of the wicking layer  76  extend into the interior of the air duct  78 , through joints  82 ,  84  of the elongated duct  78 . The joints  82 ,  84  join first duct section  90  with second duct section  92 . It is standard practice in the art to assemble a convention air duct by joining two, “L-shaped” sections of the duct together in this manner via zippered joints. Although two inner wicking layer sections are shown, it may be desirable to have only one wicking layer section extend into the duct (not shown). In the alternative, more than two wicking layer sections may extend into the duct as well. 
   The insulation blankets described herein preferably, have an outer facing layer  35  ( FIG. 1 ),  36  ( FIG. 2 ),  67 , ( FIG. 5 )  80 , such as an outer Foil Reinforced Kraft (FRK) layer  35  or other facing layers which provide a vapor retarding layer. Such vapor retarding facing materials are typically made of polymeric or composite materials. 
   It will be appreciated, however, that the laminated insulation blanket may have any suitable outer facing layer, such as an outer foil layer or an outer kraft layer, or the laminated insulation blanket may be unfaced. 
   The principle and mode of operation of this invention have been described in its preferred embodiments. However, it should be noted that this invention may be practiced otherwise than as specifically illustrated and described without departing from its scope.