What Is Extruded Polystyrene Insulation (XEPS)?
There are four major rigid plastic foam insulations commonly used for residential, commercial and industrial insulation: extruded polystyrene (XEPS), expanded polystyrene (EPS), polyurethane (PUR), and polyisocyanurate (PIR). Each type has individual characteristics and specific advantages and disadvantages for particular building applications.
Nonetheless, the stable properties of polystyrene, when combined with a unique foam extrusion process, produce an exceptionally useful product with benefits for nearly all construction and engineering applications.
Extruded polystyrene has a well established reputation for long-term reliability and superior resistance to the elemental forces of nature: time, water, cold, heat, and pressure.
Consider these forces when choosing insulation types.
THE EXTRUSION PROCESS
Extruded polystyrene foam begins with solid polystyrene crystals. The crystals,
along with special additives and a blowing agent, are fed into an extruder.
Within the extruder the mixture is combined and melted, under controlled
conditions of high temperature and pressure, into a viscous plastic fluid. The
hot, thick liquid is then forced in a continuous process through a die. As it
emerges from the die it expands to a foam, is shaped, cooled, and trimmed to
dimension.
This continuous extrusion process results in a unique foam product with a uniform closed-cell structure, a smooth continuous skin, and consistent product qualities, qualities unequaled by other insulation types.
Comparing Insulation Properties
THERMAL PROPERTIES
The ability of an insulation to resist heat flow is usually the
principal consideration in comparing insulations. The material's resistance to
heat flow is expressed as R-value. The higher the R-value, the greater the
insulating power.
However, each insulating material's R-value may vary depending upon the characteristics of its manufacture and conditions of use. In particular, the responsible design professional should consider the long-term aged R-value of installed insulations, as well as the R-value at the average use temperature, when specifying insulations.
The insulation value of most rigid foam boardstock products relies in part on the blowing agent used during their manufacture. The permeation of air, which is more conductive, into the board after manufacture can affect the R-value of the insulation with time. For accurate comparisons and for reliable performance over the life of a building or insulating product, it is important to use appropriate long-term aged R-value data from all insulation manufacturers.
DiversiFoam Products and XEPS industry organizations continue to recommend that design professionals and specifiers use long-term aged values for comparison and design calculations.
Also, the R-values of various insulation types change with different average use temperatures. However, since different types do not vary linearly or proportionally to other types, R-values at representative use temperatures should be used for accurate comparison. Specifically, some insulations with relatively high R-values at warm temperatures lose insulating power as the temperature drops. Note that CertiFoam extruded polystyrene actually has greater insulating power (higher R-value) as the mean temperature drops.
MOISTURE RESISTANCE AND MECHANICAL PROPERTIES
The superior moisture resistance of extruded polystyrene insulation
provides outstanding benefits for most construction and engineering
applications.
The universal physical and chemical properties of water can have serious consequences for many building materials. Fortunately, the superior moisture resistance of extruded polystyrene foam insulation is well established. Not only is polystyrene naturally hydrophobic (no chemical affinity for water), but its fine closed-cell structure and smooth continuous skin helps the foam resist moisture better than other types of insulating materials.
Temperature fluctuations, above and below freezing, in the presence of moisture have serious consequences for most building materials. However, the characteristic moisture resistance of extruded polystyrene foam, combined with its tough yet resilient nature, results in excellent resistance to freeze/thaw damage.
Extruded polystyrene foam is easy to handle and available in a variety of sizes and compressive strengths to suit varied application requirements.
These and other characteristics also make extruded polystyrene foam insulation the proven product choice for below grade insulation, protected membrane roof or plaza systems and a number of special insulation applications. The uniquely resistant and durable qualities, inherent to extruded polystyrene foam, make CertiFoam one of the most dependable long-term insulation materials available.
OTHER PROPERTIES
CHEMICAL RESISTANCE
CertiFoam brand insulation is recognized as a stable polystyrene
plastic foam product and is resistant to many common chemicals such as: acids,
bases, water and water-based paints, alcohol and alcohol-based paints, brine or
salt water, cement and mortars, asphalt, etc. However, petroleum-based products
may attack the foam. Avoid foam contact with concentrations of solvents such as:
Aromatic and chlorinated hydrocarbons, gasoline or fuel oil, cut-back asphalts,
naphthas or paint thinner, oil-base paint, oil-base insecticides or wood
preservatives, polyester resins, etc.
SOIL COMPATIBILITY
CertiFoam is unaffected by substances normally found in soil (i.e.
acids, alkalis, bacteria, etc.) It will not corrode, rot, or support the growth
of mold, mildew or soil microorganisms. It has no food value and will not
support plant or animal life. Precautions should be taken when insulation is in
contact with the soil to prevent hidden entry through the foam by vermin or
insect pests.
OUTDOOR EXPOSURE AND STORAGE
CertiFoam is not affected by the weather and may be stored outside.
Prolonged exposure to UV radiation in sunlight may cause the surface to become
pale and dusty. This will have no significant effect on insulating value unless
the surface is eroded and thickness is reduced. Surface dust should be brushed
off before applying adhesives or finishes. An opaque protective covering should
be used for extended outdoor exposure periods.
SERVICE TEMPERATURES
CertiFoam is not recommended for uses where sustained temperatures will exceed
165°F. Avoid contact with chimneys, steam pipes, electrical or sauna heaters or
other such surfaces. Intermittent exposure during installation and use should
not exceed 180°F. Caution should be taken to avoid prolonged excessive
temperatures under unballasted roof membranes or during roof construction
delays.
COMBUSTION PRECAUTIONS
Like many construction materials, CertiFoam brand
insulation is combustible and may constitute a fire hazard if improperly
installed. Although CertiFoam contains a flame-retardant additive to inhibit
ignition from small fire sources, it should not be exposed to open flame or
other ignition sources during shipping, storage, installation or use. These
products should not be left exposed in the interiors of buildings where people
reside, work or assemble. An approved thermal barrier, such as one-half inch
gypsum board or its equivalent, should be mechanically attached over the foam in
interior applications. Recommendations of fire and building codes should also be
followed.