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Physical Properties of EPS Insulation

* R-value means the resistance to heat flow. The higher the R-value, the greater the resistance to heat flow.

Long Term Insulation Value
R-value means the resistance to heat flow. The higher the R-value, the greater the resistance to heat flow. EPS insulation (0.90 pcf) provides a typical R-value of 3.60 per inch at a mean temperature of 75 degrees F and a typical R-value of 4.00 per inch at a mean temperature of 40° degrees F. When properly installed and protected from moisture, the R-value of EPS insulation remains constant. This is because the closed cell structure of EPS contains only air. The R-value of EPS will not decrease with age. As a result, the thermal resistance or R-value, of EPS may be used without any adjustment for age.

Moisture Resistance
Water vapor transmission through insulation materials is the passage of water through the material in the vapor phase. In comparison to other common building materials, EPS insulation has moderate water vapor permeability per unit of thickness. Recommended design practices for walls and foundations should be followed in the selection of vapor and moisture barriers for severe exposures.

A study by the Energy Materials Testing Lab (EMTL) has shown that EPS insu-lation installed in well-constructed roofs does not absorb appreciable moisture, even under conditions characteristic of prolonged, cold, damp winters. The small amount of moisture has little or no effect on the compressive or flexural strength, and the EPS insulation retains between 95% and 97% of its thermal efficiency.

Each roof application should be studied to determine the need for a vapor retarder to control internal condensation. Based on NRCA/MRCA-sponsored studies, vapor retarder placement for EPS insulated roof systems is less critical than for other types of roof insulations.

Temperature Cycling
EPS is able to withstand the rigors of temperature cycling, assuring long-term performance. In a series of tests conducted by the Dynatech Research and Development Co., Cambridge, MA, core specimens removed from existing freezer walls, some as old as 16 years, demonstrate EPS withstands freeze-thaw cycling without loss of structural integrity or other physical properties.

Strength Characteristics
For foundation and wall applications in which EPS bears a minimal load, ASTM C578 Type I EPS material is adequate. The resilience of EPS insulation board provides reasonable absorption of building movement without transferring stress to the outer skins at the joints. In most roofing applications, Type 1 EPS insulation material provides the dimensional stability and compressive strength necessary to withstand normal roof traffic and equipment weight. If greater rigidity and strength are needed, as a result of design loads, higher density EPS insulation products are available. Please contact Insulation Technology for recommendations regarding your particular application.

Combustibility
Like many construction materials, EPS is combustible. EPS products are manufactured with a flame retardant; however, EPS insulation will burn upon exposure to flame or heat sources, including, but not limited to, open flames, welder's torches, or other sources of heat. EPS insulation should be covered with a thermal barrier or otherwise installed in accordance with applicable building code requirements. It is the responsibility of the purchaser to ensure that EPS insulation is properly handled and stored on the jobsite.

Solvent Attack
EPS is subject to attack by some petroleum-based solvents. Care should be taken to prevent contact between EPS and these solvents and their vapors.

Application Temperatures
In roof construction requiring hot asphalt, temperatures should not exceed 250 degrees F at the time of direct contact with EPS insulation. Avoid contact between EPS and high-temperature equipment, such as asphalt kettles and flame sealers.

Installation Exposure
Prolonged exposure to sunlight will cause slight discoloration and surface dusting of EPS insulation. The insulating properties will not be significantly affected under normal usage. EPS stored outside should be protected with a light-colored opaque material.

Standards Compliance
EPS insulation may be manufactured to meet or exceed the requirements of ASTM C578 and applicable building codes.

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