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.

1. Customer Bulletin 0610 June 2010
CUSTOMER BULLETIN 06-10
POLYISOCYANURATE 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

2. Customer Bulletin 0610 June 2010
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;

3. Customer Bulletin 0610 June 2010
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 insulation

4. Customer Bulletin 0610 June 2010
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.]

5. Customer Bulletin 0610 June 2010
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 prudent

6. Customer Bulletin 0610 June 2010
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
Water Absorption % by volume 0.043
0.24
3
As measured in a 24-hour test per ASTM C272
4
As measured in a 2-hour test per ASTM C240

7. Customer Bulletin 0610 June 2010
Qualitative Comparison Chart:
Quality ISO-C1 FOAMGLAS
Thermal Performance Excellent Fair
WVT without vapor barriers Very good Excellent
WVT with vapor barriers Excellent Excellent
Available with factory-applied
vapor barrier
Yes Possibly, for smaller sizes
Closed cell structure Yes Yes
Fiber free Yes Yes
Non-porous Yes Yes
Mold resistant Yes Yes
Very Resistant to
vibration/movement
Yes No
Recommends a jacket Yes For most applications
Thicknesses available Virtually unlimited,
from 1/2” upwards
Limited, 1” minimum
Lengths Virtually any Sold in 2 foot maximum