To start, we need to define “water vapor retarder”
\nand “jacketing.” ASTM C168 gives this definition for the former:<\/p>\n
Water vapor retarder
\n(barrier), n—<\/b>a material or system that significantly impedes the
\ntransmission of water vapor under specified conditions. <\/p>\n
Water vapor retarders are used
\nto limit the rate of water vapor migration from the ambient to a below ambient
\nsurface. This is depicted in Figure 1.<\/p>\n
A water vapor retarder may or
\nnot include a separate protective jacket. However, for insulation materials
\nwith high vapor permeability, there must be a continuous, tightly sealed vapor
\nretarder surrounding the insulation. As long as the pipe remains cold and the
\nenvironment is warm and humid, a vapor pressure difference will exist between
\nthe environment and the pipe surface.<\/p>\n
ASTM C168 defines a jacket as
\nfollows:<\/p>\n
jacket, n—<\/b>a covering
\ninstalled over insulation.<\/p>\n
Traditional Indoor Jacketing and Vapor Retarders<\/font><\/b><\/p>\n Jacket, or jacketing, exists in Failure Mechanisms of Vapor Retarder Systems<\/font><\/b><\/p>\n One reason for the development of new water vapor <\/UL><\/p>\n Figures 4 through 7 show While ASJ can be a good vapor Failures commonly encountered usually involve either unprotected, Furthermore, in mechanical ASTM C1136 Vapor Retarders<\/font><\/b><\/p>\n Traditional indoor vapor retarders have been Examining these values, it is apparent that this new ASTM C1136 Type IX There is also a category of new Joints<\/b><\/p>\n Achieving a <\/UL><\/p>\n Figures 13 and 14 show some of On insulated ducts, laminate Removable and Reusable Insulation for Components<\/font><\/b><\/p>\n With the availability of the ASTM C1136 Type IX Using a special insulation kit Some in the insulation industry Summary<\/font><\/b><\/p>\n With the recent development of very low permeance
\ndifferent forms, as shown in the photos in Figures 2 and 3. <\/p>\n
\nretarders is the incidence of insulation systems failing on below ambient pipe
\nequipment in unconditioned buildings. This is a particular problem in locations
\nwhere the climate tends to be hot and humid. When a failure occurs on a below
\nambient system with a sheet type of vapor retarder, it is likely due to at
\nleast one of the following failure mechanisms:<\/p>\n<\/p>\n
\nmigration though holes in the aluminum foil in the vapor retarder (pin holes or
\nlarger)<\/p>\n
\nmigration through joints in the vapor retarder (closures)<\/p>\n
\non the surface soaking into exposed paper on the all-service jacketing (ASJ)
\nwhen traditional ASJ is used (e.g., a Kraft paper—glass fiber scrim—0.00033
\ninch thick aluminum foil laminate) and not covered. This condensation may lead
\nto deterioration of the ASJ.<\/p>\n
\nwhich also may pose perceived or actual health and safety problems (the
\nspecifics of which are beyond the scope of this article)<\/p>\n
\nphotographs of some of these problems. <\/p>\n
\nretarder, it is important that it be used in building spaces that are
\nconditioned and maintain low absolute humidity levels. Photos 4 through 7,
\nshowing failed CHW insulation systems, were all taken in spaces that were
\nunconditioned most or all of the time. ASJ usually covers fiberglass or
\nphenolic foam pipe insulation, all of which have sufficiently high vapor
\npermeability values that they require a separate, continuous, tightly sealed
\nvapor retarder for successful performance.<\/p>\n
\ntraditional ASJ, or ASJ covered with unsealed polyvinyl chloride (PVC) in
\nunconditioned spaces in buildings located in hot and humid climates. There is
\nevidence that continuously sealed PVC jacket (either with solvent or PSA tape)
\ncan significantly improve the vapor performance of ASJ in such applications.
\nSealed PVC, installed over traditional ASJ, provides 3 major advantages over
\nexposed traditional ASJ: (1) lower system permeance, (2) water resistance, and
\n(3) physical protection. However, when the PVC is not continuously sealed in
\nthese applications, that PVC jacketed system, on top of traditional ASJ, also
\nfrequently fails in unconditioned spaces such as mechanical rooms and central
\nCHW plants.<\/span><\/p>\n
\nrooms of buildings, traditional ASJ is frequently exposed to physical abuse,
\nincluding dripping or spraying water, which further shortens its life. It is likely
\nthat exposed, traditional ASJ will not last long in a mechanical room
\nenvironment due to expected physical exposure. In any unconditioned space,
\ntraditional ASJ does not perform well unless covered with a continuously sealed
\nPVC jacket. The results of research currently being conducted at Oklahoma State
\nUniversity for ASHRAE Technical Committee 1.8 as Research Project RP-1646
\nshould soon provide data to clarify some of these performance issues.<\/p>\n
\naddressed by ASTM specification C1136. These include ASJ, foil-scrim-kraft
\n(FSK), metalized polyethylene teraphthalate (MPET), and polyvinylidene chloride
\n(PVdC) materials. PVC jacket is not covered by C1136. Last year, ASTM added a
\nnew Type IX material that is rated as having a water vapor permeance of 0.00
\nperm (meaning test results by ASTM E96 yield a permeance < 0.005 perm).
\nFigure 8 shows performance values of the recently updated C1136-12, with the
\nnew Type IX shown in red in the last column.<\/p>\n
\nvapor retarder also has greater burst strength than the other vapor retarders,
\nand it has an average tensile strength. This material has a permeance of 0.00
\nperm because its composition includes aluminum foil with a thickness of at
\nleast 0.001 inch (1 mil), which is at least 3 times thicker than the foil used
\nin traditional ASJ. An additional feature is that its composition includes no
\nexposed paper.<\/span><\/p>\n
\nvapor retarders for use outdoors. Two specifications are under development at
\nASTM Committee C16: one for a new product called “laminate protective jacket
\nand tape,” and another for a product called “modified asphalt jacket.” While
\nthese are not always used as vapor retarders, like the ones covered by ASTM
\nC1136, all are rated as having a permeance of 0.00 perms. In addition, they are
\nmuch stronger than the Type IX vapor retarders, having burst strengths up to
\n400 pounds per square inch (psi) (compared to 70 psi for the C1136 materials)
\nand tensile strengths up to 150 psi (compared to 45 psi for the C1136
\nmaterials). While all are available with an aluminum finish, either smooth or
\nembossed, some are also available in different colors such as white, black, and
\ngray. Figures 9 through 12 show photos of these type materials in various
\napplications.<\/p>\n
\nsuccessful performance from a vapor retarder systems made with these or other
\nmaterials requires the following:<\/span><\/p>\n<\/p>\n
\nincluding vapor dams<\/p>\n
\nhigh-quality materials<\/p>\n
\ninstallation, with attention to providing continuous sealing, especially at
\nclosures<\/p>\n
\noperations and maintenance by facility owner<\/p>\n
\nthat all systems have a limited life (not likely more than 30 years and
\nprobably less for systems in high-humidity conditions)<\/p>\n
\nthe steps for sealing pipe or cylindrical duct insulation jacketing using
\ncompatible tape with a pressure sensitive adhesive (PSA).<\/p>\n
\nprotective jacket and tape can be used to weatherize the insulation system and,
\nin the process, provide a vapor tight seal. Figures 15 and 16 show installation
\ndetails.<\/p>\n
\nvapor retarder and tape, both of which
\ninclude a PSA, it is now possible to make and apply a removable\/reusable
\ninsulation system on pipe system components in mechanical rooms. Sometimes
\nthese components (butterfly valves, flange pairs, vibration
\nisolators, etc.) were insulated during construction, but when one of the
\nfittings leaks, mechanical maintenance personnel might cut off the insulation
\nand discard it to replace the leaking gasket or vibration isolator. The
\nindividual replacing the parts may not reinsulate the components. In other
\ncases, these components were never insulated in the first place. Regardless,
\nthe penalty for having no insulation on these components is energy waste and,
\nat least during much of the year, excessive condensation and subsequent
\ncorrosion of the metal surfaces.<\/span> <\/p>\n
\nmade with a continuous vapor retarder on both sides of a flexible blanket, and
\nwith matching PSA and vapor retarder tape, custom shapes can be made by the insulation
\ncraft laborers in the field and then installed on previously bare components.
\nWhen future removal is required for mechanical maintenance, some of the tape
\ncan be removed, the insulation removed, the maintenance performed, and the
\ninsulation then reinstalled (preferably by skilled insulation craft laborers)
\nusing fresh tape. This saves time and money and reduces damage to the
\ninsulation system. Figures 17 and 18 show before and after photos using this
\ntype of kit made using an ASTM C1136 Type IX vapor retarder.<\/p>\n
\nhave objected to the less trim and consistent appearance of removable\/reusable
\nkit insulation after installation. In its defense, the traditional appearance
\nis sacrificed to achieve removability and reusability, features that allow for
\nmechanical maintenance without damage to the system, reuse of the mechanical
\ninsulation materials each time they are removed, and an insulation system that
\ncan be tightly sealed against water vapor intrusion. However, there are other
\nproduct options available for components, including valves. The most important
\nthing is to insulate the whole system. Figures 19 and 20 show some of these
\npossibilities.<\/p>\n
\nvapor retarders, new options have emerged for jacketing insulation systems.
\nThese new materials have been designed for both indoor and outdoor use. All
\nhave a permeance of 0.00 perm, and most are stronger—some much stronger—than
\ntraditional vapor retarders. Many are available with pressure-sensitive
\nadhesives, and all have compatible tape with a PSA. It is now common to see
\noutdoor, insulated ducts with these new vapor retarders, and sometimes outdoor
\ninsulated pipe and equipment. The use of the new ASTM C1136 Type IX vapor retarders,
\nwith PSA tape, allows for tightly sealing the vapor retarder systems. This
\nmaterial has also allowed for the development of a kit for making
\nremovable\/reusable insulation blankets for use on CHW mechanical room
\ncomponents.<\/p>\n
![](\"https:\/\/insulation.org\/wp-content\/uploads\/2017\/06\/IO130703_01.jpg\")
<\/a>Figure 1<\/b><\/div>\n