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EPS expanded-polystyrene-thermal-insulation

Expanded PolyStyrene (EPS) is a white foam plastic material produced from solid beads of polystyrene. It is primarily used for packaging, insulation etc. It is a closed cell, rigid foam material produced from Styrene - which forms the cellular structure, and Pentane - which is used as a blowing agent

Both styrene and pentane are hydrocarbon compounds and obtained from petroleum and natural gas byproducts.

EPS is Extremely Lightweight, has Very Low Thermal Conductivity, Low Moisture Absorption and Excellent Cushioning Properties. It is 98% air and 100% recyclable.

Its physical properties do not change within its service temperature range (i.e. up to 167°F/75°C) for long term temperature exposure.

One of the serious limitations of polystyrene foam is its rather low maximum operating temperature of about 80°C.

Contractor installing recycled and new styrofoam boards from the Ohio Insulation King depot

The term Styrofoam™ is often used to describe Expanded Polystyrene (EPS) foam; however, Styrofoam™ is actually a trademarked BRAND of closed-cell extruded polystyrene foam made by DuPont, for thermal insulation and craft applications.


EPS Foam is the correct term for any form of Expanded Polystyrene.

Graphic with checkmark, positive  green light affirmation for EPS installation
  • Light Weight - A 8ft x 4ft x 2.5in sheet of Type-1 EPS foam board typically weighs about than 2.83kg.

  • Thermal Properties (insulation) - EPS has very low thermal conductivity due to its closed cell structure. In fact, EPS is 98% air! This air trapped within the cells is a very poor heat conductor and giving EPS foam excellent thermal insulation properties.

    The thermal conductivity of expanded polystyrene foam of density 20 kg/m3 is 0.035 – 0.037 W/ (m·K) at 10 °C.

    ASTM C578 Standard Specification for Rigid Cellular Polystyrene Thermal Insulation addresses the physical properties and performance characteristics of EPS foam as it relates to thermal insulation in construction applications.

  • Temperature Cycling - EPS is able to withstand the abuse of temperature cycling, assuring long-term performance. In a series of tests conducted by Dynatech Research and Development Co., Cambridge, Mass., 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.

  • Mechanical strength - Flexible production makes EPS versatile in strength which can be adjusted to suit the specific application. EPS with high compressive strength is used for heavy load bearing applications, whereas for void forming EPS with a lower compressive strength can be used.

    Generally, strength characteristics increase with density, however the cushioning characteristics of EPS foam packaging are affected by the geometry of the molded part and, to a lesser extent, by bead size and processing conditions, as well as density.

  • Dimensional Stability - EPS offers exceptional dimensional stability, remaining virtually unaffected within a wide range of ambient factors. The maximum dimensional change of EPS foam can be expected to be less than 2%, which puts EPS in accordance with ASTM Test Method D2126.

  • Electrical Properties - The dielectric strength of EPS is approximately 2KV/mm. Its dielectric constant measured in the frequency range of 100-400 MHZ and at gross densities from 20-40 kg/m3 lies between 1.02-1.04. Molded EPS can be treated with antistatic agents to comply with electronic industry and military packaging specifications.

  • Water Absorption - EPS is not hygroscopic. Even when immersed in water it absorbs only a small amount of water. As the cell walls are waterproof, water can only penetrate the foam through the tiny channels between the fused beads.

  • Chemical Resistance – Water and aqueous solutions of salts and alkalis do not affect expanded polystyrene. However, EPS is readily dissolved by organic solvents.

  • Weathering and Aging Resistance – EPS is resistant to aging. However, exposure to direct sunshine (ultraviolet radiation) leads to a yellowing of the surface which is accompanied by a slight embrittlement of the upper layer. Yellowing has no significance for the mechanical strength of insulation, because of the low depth of penetration.

  • Fire Resistance – EPS is flammable. Modification with flame retardants significantly minimize the ignitability of the foam and the spread of flames.

foam-and-formwork application -beginnings of installation as floor insulation in new construction

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

EPS insulation (1.0 pcf) provides a typical R-value of 3.85 per inch (k-factor =0.26) at a mean temperature of 75°F, and a typical R-value of 4.17 per inch (k-factor = 0.24) at a mean tem-perature of 40°F.

When properly installed and protected from moisture, the R-value of EPS insulation remains constant. This is because the cellular structure of EPS contains only stabilized 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 aging.

foam-and-formwork application -beginnings of installation as floor insulation in new construction

EPS insulation is an inert, organic material produced from petroleum and natural gas by-products. EPS insulation does not contain chlorofluorocarbons (CFCs) or hydrochlorofluorocarbons (HCFCs).


It is manufactured with hydrocarbon blowing agents. It provides no nutritive value to plants, animals or micro-organisms. It will not rot, and is highly resistant to mildew.

EPS is 100% recyclable. After its original life as insulation, EPS could be recycled into a variety of consumer and indus-trial products. Many EPS molders have been reprocessing their own in-plant scrap for many years. An infrastructure for the collection of EPS is being developed, making it possible to produce products containing post consumer recycled EPS materials. EPS molders can now provide you with a place to return scrap EPS construction insulation as well as offer recycled content products when specified or desired.

EPS Insulation Boards can also be reclaimed and reconditioned and redeployed as a much cheaper alternative to brand new EPS boards.

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