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Customer Bulletin 0610 Polyisocyanurate vs. Cellular Glass Insulation


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This Customer Bulletin is another in our series of white papers aimed at providing our clients, engineers, contractors, fabricators, and friends with objective information on our products and those of our competitors. This Bulletin focuses on a comparison of the physical properties of closed cell polyisocyanurate (PIR or polyiso) rigid foam insulation with those of cellular glass insulation for below ambient applications such as chilled water through cryogenic application where moisture intrusion or condensation can be an issue.

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Customer Bulletin 0610 Polyisocyanurate vs. Cellular Glass Insulation

  1. 1. CUSTOMER BULLETIN 06-10POLYISOCYANURATE VS. CELLULAR GLASS INSULATION PURPOSE This Customer Bulletin is another in our series of white papers aimed at providing our clients, engineers, contractors, fabricators, and friends with objective information on our products and those of our competitors. This Bulletin focuses on a comparison of the physical properties of closed cell polyisocyanurate (PIR or polyiso) rigid foam insulation with those of cellular glass insulation for below ambient applications such as chilled water through cryogenic application where moisture intrusion or condensation can be an issue. Dyplast’s ISO-C1®1 polyiso and Pittsburgh-Corning’s FOAMGLAS® 2 were selected for comparison since they were each judged best-in-class. The result of the comparison was that ISO-C1 is the ideal choice for applications ranging from minus 297°F up to plus 300°F service temperature - - such as chilled water, refrigeration, HVAC, domestic hot and cold water and cryogenic applications. Note that while this Bulletin is focused on differences between FOAMGLAS and ISO-C1, there are indeed differences between the physical properties and performance characteristics of competing PIR insulations. We recommend end-users view other Customer Bulletins from Dyplast that address these differences. SUMMARY K-factor: The aged thermal conductivity (k-factor) at 75°F of ISO-C1 polyiso is 0.176 Btu·in/hr·ft2·°F whereas FOAMGLAS brand cellular glass is 0.29. Thus the thermal insulation performance of cellular glass is roughly 65% worse than polyiso, which results in cellular glass insulation systems being much thicker (important from a weight, cost, and space aspect). Brittleness: Cellular glass is susceptible to vibration, movement, thermal shock, and mechanical shock. Cellular glass may be unsuitable for application in process environments with high vibration, movement, or thermal/mechanical shock. During installation, if cellular glass is dropped it may shatter; also if metal banding is applied to tightly cell glass can break, or if banding has a coefficient of expansion different than cell glass it could crack the insulation during a thermal cycle. If cellular glass breaks the cracks may create a path for heat and/or 1 ISO-C1 is a registered trademark of Dyplast Products, LLC; a usage of ISO-C1 without the ® symbol is not intended indicate any relinquishment of Trademark Rights 2 FOAMGLAS, PITTCOTE, and PITTWRAP are a registered trademark of Pittsburgh-Corning Corporation; a usage of any Mark without the ® symbol is not intended indicate a relinquishment of Trademark Rights Customer Bulletin 0610 June 2010
  2. 2. moisture to pass, thus compromising the insulation system; whereas polyiso is not brittle and is not as susceptible to vibration, movement, or thermal/mechanical shock. When ISO-C1 is installed in areas where mechanical abuse is expected (such as workers stepping on the insulation), higher density polyiso with its higher compressive strengths may be considered. Even when abused, normal 2.0 lb/ft3 density polyiso is not brittle and it does not crack or shatter like cellular glass. Cellular glass is even prone to damage during shipping and handling unless packaged in suitable cartons with spacers, whereas polyiso can be thrown into poly bags and shipped with minimal damage, thus materially reducing packaging and shipping costs, and related waste.Water Absorption: Measurement per ASTM C272 (Method A), which requires a 24 hour immersion period, demonstrates ISO-C1 (2 lb/ft3 density) has a 0.04% by volume water absorption. The comparable FOAMGLAS test per ASTM C240 requires only a 2 hour immersion, and the FOAMGLAS results are 0.2% by volume. Thus it is clear that FOAMGLAS has no advantage in water absorption.Installation – the “insulation system”: A particular insulation product can perform at its peak only when properly installed within a more complete “insulation system” with sealants, adhesives, vapor barriers, mastics, jacketing, and so forth. A cellular glass insulation system is generally more complex than a comparable polyiso insulation system and thus is more labor- intensive to install - - with the result that there is more potential for errors during the installation process. For example: Since the lengths and diameters of FOAMGLAS insulation segments are smaller than those of polyiso (18”x24”x7” maximum), there will be more segments (pieces) of FOAMGLAS to install as compared to a polyiso system. Even for small-bore pipe, FOAMGLAS will be delivered in maximum 2-foot sections, while ISO-C1 is typically fabricated in 3-foot sections (and could conceivably be longer). More pieces and parts means more seams and joints to seal, which means more labor, more consumption of materials, and more possibility of improper installation (e.g. a seam not sealed, or a cracked piece of insulation) - - which can lead to thermal and/or moisture leaks. A FOAMGLAS insulation system is also likely to have more layers than a comparable polyiso system thus requiring more steps in the process, more joints to seal, and resulting in more consumption of sealants, tapes, adhesives, etc.; According to manufacturer’s installation recommendations, a typical FOAMGLAS system in a low temperature application may require a coat of mastic (3 to 4 gal./100 ft2 either sprayed or trowelled), then a layer of synthetic mesh fabric, and then a second coat of mastic. An ISO-C1 system installation, on the other hand, requires only a vapor barrier sheeting applied over the insulation - - and this could actually be shop applied, making field assembly even easier; Bore Coatings may be required where FOAMGLAS abrasion may erode the pipe; Mixing of 2-component adhesives require extra steps and time, and may contain carcinogens that require special ventilation or other respiratory protection;Customer Bulletin 0610 June 2010
  3. 3. Although ISO-C1 and FOAMGLAS both generate dust during fabrication or in-field shaping, cellular glass is considered particularly problematic, and sometime vacuuming is suggested in FOAMGLAS installation instructions.Weight: FOAMGLAS can vary in density but typically is supplied at 7.5 lb/ft3 - - a density close to 4 times that of 2 lb/ft3 polyiso. The low thermal efficiency of cellular glass (65% worse than polyiso) compounds the problem since cellular glass installations may require almost double the thickness. The result is a major increase in weight and volume on a given pipe run. [For example assume a 12” diameter run of piping requiring 4” of polyiso insulation at 2 lb/ft3 density; every linear foot of insulation would weigh 2.8 lbs; even ignoring humidity, wind, etc. 6.6 inches of cellular glass must be applied to achieve the same R-value, resulting in the weight of a linear foot of cell glass approaching 20 lbs per linear foot- - 7 times more weight than polyiso]. The costs of additional pipe hangars, stress on joints that can lead to failure, and inability to run multiple pipes in a small space make cellular glass a challenging insulation.Size of insulation blocks/segments: Polyiso bunstock is manufactured as large continuous “buns”. ISO-C1 bunstock production equipment can be adjusted to produce variable block dimensions depending on particular customer needs. Bun widths for a nominal 2 lb/ft3 density can vary from a trimmed 38 inches up to a trimmed 52 inches, with standard sizes set at 48 inches. Bun lengths can vary from 36 inches (standard pipe chunks) up to 288 inches. The bun heights for other ISO-C1 densities will vary. The largest FOAMGLAS blocks are produced with dimensions 18 x 24 x 7 inches. The smaller dimensions will limit the size of the pipe insulation segments, thus requiring more segments to insulate pipe, and more seams/joints.Vapor Barriers: Vapor drive is increasingly a major problem at lower process temperatures. From refrigerant to cryogenic temperatures vapor drive can be severe and lead to failure of the insulation system without a properly installed vapor barrier system. FOAMGLAS advertises a water vapor transmission of “0” perm-inch per ASTM E96. ISO-C1 has excellent WVT at 1.65 perm-inch, yet not zero. Engineers and end-users, however, agree that the permeability of the fully-installed insulation system is the ultimate objective - - while mitigating life-cycle permeability risks created by poor installation, joint failures, mechanical abuse, thermal cycling, degradation of material performance over time, etc. ISO-C1 installations have fewer pieces/parts, fewer joints, are less susceptibility to cracking/shattering, and have excellent life- time performance. In all low-temperature pipe and equipment insulations, both FOAMGLAS and ISO-C1 installation guidelines indicate a vapor barrier should installed over the insulation. ISO-C1 installation guidelines are consistent with other polyiso manufacturers, engineers, and contractors, recommending a properly installed zero-perm vapor barrier wrap over lengths of pipe (which can be factory-applied or field-applied). Installation guidelines for FOAMGLAS recommend, depending on the application, either a vapor retarder mastic (sometimes in 2 trowelled/sprayed layers with mesh in between) or a vapor retarder wrap - - unless conditions are “mild below ambient” where a 2-layer weather barrier mastic or even a metal jacket without mastic is deemed adequate. We would caution end-users to consult their insulationCustomer Bulletin 0610 June 2010
  4. 4. engineer. Note also that the manufacturer of FOAMGLAS states that with an “asphalt bonded fabrication, with all joints of the outermost layer of FOAMGLAS insulation completely sealed and drawn tight, the system is vapor sealed and no additional vapor barrier is required”. End- users should be aware, however, that asphalt bonding can not be used in many lower temperature applications, and end-users should be cautious of having no backup vapor barrier available if a joint opens or crack appears.Jacketing: ISO-C1 installation guidelines are again consistent with major engineering companies and insulation contractors, generally recommending a metal jacket to protect the insulation system from mechanical abuse and weather-related insult/wear. PVC jacketing may be appropriate when frequent wash-downs or FDA cleanliness requirements dictate. Yet end- users should note that an ISO-C1 insulation system, similar to FOAMGLAS systems, can perform well without a jacket if mechanical abuse or weather is not a problem. FOAMGLAS installation guidelines also require a metal jacket in all cases where the insulation system will be exposed to ultraviolet light.Combustibility and Flame/Smoke: Although cellular glass is advertised as having a zero flame spread index (FSI) and a zero smoke developed index (SDI) per ASTM E84 testing, either the recommended vapor retarders, weather barriers, sealants, mesh, or adhesives typically specified with cellular glass may be flammable or prone to emit smoke during fires. For example both PITTCOTE® 300 (asphalt mastic), PITTWRAP® CW300 (non-metallic jacket), and PC® product data sheets indicate they are combustible. [Note that some liquid products may be combustible while they are being applied, yet may not be after they have cured]. Note also that cellular glass can shatter and lose its insulating integrity when thermally shocked. Although ISO-C1 has a 25/130 FSI/SDI rating at a thickness of 4 inches, when exposed to flame, ISO-C1 insulation will char yet maintain its shape long enough to provide precious minutes of thermal protection to pipe, equipment, and vessels to allow response. [Important Note: Section 602.2.1 of the International Mechanical Code states that materials within return air plenums shall be either non-combustible or have a 25/50 fire spread index and developed smoke index when tested in accordance with ASTM E84. Interpretations by other code authorities have allow compliance with NFPA 255 or UL 723 as substitutes for ASTM E84. Essentially this means that insulation systems (and all accessory components within, such as sealants, vapor barriers, etc.) installed in either air plenums or inhabited areas to be non-combustible or ≤ 25/50. Name- brand cellular glass such as FOAMGLAS meets this 25/50 requirement. ISO-C1 polyiso is 25/130, so it should not be installed in air plenums or in indoor inhabited areas. Caution should be observed that when using cellular glass in such applications that all related sealants, barriers, and such are ≤ 25/50.]Customer Bulletin 0610 June 2010
  5. 5. WVT (Water Vapor Transmission, or permeability): ISO-C1 has excellent WVT at 1.65 perm- inch, yet not zero as advertised for FOAMGLAS. Engineers, contractors, and end-users generally contend, however, that it is more important to consider the permeability of the entire installed insulation system. The greater number of joints, added complexity of installation that can lead to mistakes, propensity for shattering, short life-time performance of sealants and adhesives, and so forth can override any intrinsic permeability of FOAMGLAS. On the other hand, ISO-C1 is easily installed with a zero-perm vapor barrier that can be either factory- applied or field-applied. The final installed system generally has fewer joints than a similar cellular glass system, and is less prone to failure.Cost: The material costs of ISO-C1 are roughly half that of FOAMGLAS. Considering the additional costs associated with the installation of cellular glass (both labor and pieces/parts), the overall installed cost of cellular glass can easily be 3 or more times expensive than polyiso; life-cycle costs relating to energy loss and maintenance also will favor polyiso over cellular glass.Chemical resistance: Cellular glass is often advertised as being impervious to chemicals and is indeed resistant to organic solvents and nearly all acids. Yet polyiso insulation can be used to insulate piping and vessels containing almost any material, and is suitable for use where incidental contact with most solvents and chemicals is possible.Compressive strength: Cellular glass indeed has high compressive strength commensurate with its weight and brittleness. Yet ISO-C1 polyiso insulation is available in compressive strengths exceeding 125 psi, more than adequate for the vast majority of applications (e.g. pipe hangars and areas of mechanical abuse) - - while delivering thermal performance vastly superior to cellular glass - - and with fewer problems associated with cracking and weight management (see sections on brittleness and weight).Coefficient of Linear Thermal Expansion (CLTE): Cellular glass has a CLTE close to that of carbon steel, and thus requires fewer contraction/expansion joints than a polyiso insulation system. More expansion joints would be required for aluminum, copper, nickel, their alloys, and austenitic stainless steel piping. Polyiso, however, is easier to work in the field and polyiso contraction/expansion joints are relatively easy to install.Dimensional Stability: Dimensional stability is a combination of both reversible and irreversible changes in linear and volumetric dimensions. FOAMGLAS product data sheets advertise excellent to extraordinary dimensional stability, yet ISO-C1 insulations also have very good to excellent characteristics. The bottom line is that with properly installed contractions/expansion joints the issue is mute since any temporary or permanent changes in dimension can be accommodated by insulation system design. Note that some cellular glass manufacturers make comparisons against polyurethane insulation without noting that polyisocyanurate is a different chemical formulation with much improved dimensional stability; note also that ISO-C1 has the best dimensional stability when compared with competitive polyiso products.Safety: The MSDS sheets of each product utilized within any insulation system should be reviewed for potential hazards. Also, jobsites should of course establish and enforce prudentCustomer Bulletin 0610 June 2010
  6. 6. safety practices. A review of product data sheets and MSDS literature for both ISO-C1 and FOAMGLAS lead to a conclusion that FOAMGLASs and related materials required for insulation represent more hazards relating to carcinogens, combustible compounds (during storage and usage), dust, abrasion, and weight than those in a comparable ISO-C1 installation.Maintenance: All insulation systems should be part of the preventive maintenance system, checking not only for damage or deterioration, but ensuring re-installation after maintenance on insulated equipment. Insulation systems are generally compromised either by: 1. Mechanical abuse, such as personnel stepping on insulation or vehicles bumping into insulation; such abuse can dislodge jackets, puncture vapor barriers, open sealed seams between insulation segments, or crush insulation; ISO-C1 and FOAMGLAS are equally susceptible to such damage, with certain exceptions; while FOAMGLAS may have higher compressive strengths at its “standard” density, when the compressive limits are exceeded FOAMGLAS shatters and loses virtually all its thermal integrity; ISO-C1 on the other hand has more resilience, and even when deformed it will maintain some of its original performance; 2. Thermal shock, when severe, can crack or shatter FOAMGLAS, whereas ISO-C1 is not as susceptible to thermal shock; 3. Weather can result in deterioration of an insulation system in several ways; although rain alone should not be a factor, extreme winds can dislodge jacketing and can then pummel vapor barriers with wind/rain - - creating or exposing defects; UV radiation can degrade materials; although the elements of an ISO-C1 system and FOAMGLAS system are each somewhat susceptible, an ISO-C1 system may have the advantage by virtue of fewer joints, seams, and overall size; 4. Deterioration of materials is an important factor since some compounds used in the installation of FOAMGLAS may have a lifetime of 10 or so years; in such case, the performance of a sealant or mastic may be compromised. The following table displays key physical properties of polyiso (ISO-C1) and cellular glass(FOAMGLAS). Note that these are “product” values, and not “insulation system” values. Insulation Material Units ISO-C1 FOAMGLAS Thermal (at 75°F) k-factor (aged) 0.176 0.29 WVT Perm-inch 1.65 0.00 Flammability ASTM E84 rating (4 in.thick) FSI/SDI 25/130 <25/50 Density lb/ft3 2.0 7.5 3 Water Absorption % by volume 0.04 0.243 As measured in a 24-hour test per ASTM C2724 As measured in a 2-hour test per ASTM C240Customer Bulletin 0610 June 2010
  7. 7. Qualitative Comparison Chart:Quality ISO-C1 FOAMGLASThermal Performance Excellent FairWVT without vapor barriers Very good ExcellentWVT with vapor barriers Excellent ExcellentAvailable with factory-applied Yes Possibly, for smaller sizes vapor barrierClosed cell structure Yes YesFiber free Yes YesNon-porous Yes YesMold resistant Yes YesVery Resistant to Yes No vibration/movementRecommends a jacket Yes For most applicationsThicknesses available Virtually unlimited, Limited, 1” minimum from 1/2” upwardsLengths Virtually any Sold in 2 foot maximumCustomer Bulletin 0610 June 2010