EPS Polystyrene

June 13, 2020 Off By Genevieve
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Litterally translated, polystyrene is ‘ polymerised styrene”.  The expandable form (known as EPS) is initially produced as small beads containinga blowing agent. The beads expand when treated with steam, forming a lightweight “prefoam” of the required density.

These prefoamed beads are processed in a mould to form large blocks that are then cut into sheets or other shapes. Alternatively, for high volume products, the beads are moulded into their final product form in individual moulds.

Thermal insulation of buildings is becoming increasinly relevant as energy costs rise and climate change is reality. One area that acts as a thermal heat soak is the under floor area of any building drawing heat generated inside buildings into the ground. The thermal under floor system acts as a easy to install under floor insulation system as well as having a number of other functions and benefits.

Ground floor insulation – EPS is used in a multipality of applicationsfor its thermal insulating properties. The EPS sheeting acts as a thermal barrier to prevent under floor cold penetrating rooms and keeping heat generated in houses from being dissipated into the ground.

Optimisation of underfloor heating systems.

If under floor heating is installed the EPS thermal under floor system should be obligatory. EPS will ensure that heat generated is not absorbed by the ground and is forced upwards into the house itself.

Long Life – EPS is rot and rodent proof and dimensionally stable and thus will retain its thermal insulating and moisture barrier effectiveness for the life of the building.

EPS Specifications

What is EPS?

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Expanded Polystyrene, or EPS for short, is a lightweight, rigid, plastic foam insulation material produced from solid beads of polystyrene. Expansion is achieved by virtue of small amounts of pentane gas dissolved into polystyrene base material during production. The gas expands under the action of heat, applied as steam, to form perfectly closed cells of EPS. These cells occupy approximatly 40 times the volume of the original polystyrene bead. The EPS beads are then moulded into appropriate forms suited to their application.

Thermal Resistance (R-Value):

The R-Value of EPS foams can be increased by increasing the density of the product. The thermal resistance of these thermoplastic foams is generally stable over the long term and therefore the initial R-Value at the time of manufacturing will not change over time. In the construction sector, EPS has a long established reputation for its exceptionally high insulation qualities. This means EPS is the perfect choice for use in underfloor, between-floor, walling and roofing applications whereit is able to give a constant insulation value across the full service life of the building.

Fire Safety:

All EPS products, as promoted by EPSASA, fufil the requirements in accordance with the National Building Regulations SANS 10400-T Fire Protection.

Where to Use EPS?

Anyone who needs to thermally insulate walls, roofs or floors will find EPS the ideal, cost-effective and easy-to-use material in all types of buildings, from houses and offices to factories. EPS is used by civil engineers as a lightweight fill or voidforming material. It is also used as flotation material.


EPS can be recycled if it is recovered without contamination from other materials. Generally the most benefical is direct re-use by grinding clean EPS waste and adding it to virgin material during production of new foamed products.

Alternativley, EPS can be melted and extruded to make compact polystyrene, for items such as plant pots, Coat hangers and a wood substitute. Medium toughened polystyrene from which sheets for thermoformed articles such as trays, can also be made. As part of mixed plastic waste, EPS can be recycled to make, for example, park benches, fence posts and road signs, ensuring the plastic material has a long and useful second life.

Thermal Requirements in accordance with SANS 204:


With the exception of Zone 5, buildings with a floor area of less than 500m², with a concrete slab-on-ground, shall have insulation installed around the vertical edge of its perimeter which shall:

  1. have an R-value of not less than 1,0.
  2. resist water absorption in order to retain its thermal insulation properties, and
  3. be continuous from the adjacent finished ground level
  • to a depth of not less than 300mm, or
  • for the full depth of the verticle edge of the concrete slab-on-ground.
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Where an underfloor (in-screed, under floor heating, under laminate heating, under carpet heating, under tile heating, cut-in under floor heating or water based underfloor heating) heating system is installed, the heater shall be insulated underneath the slab with insulation that has a minimim R-value of not less than 1,0.

With the exception of climatic zone 5, a suspended floor that is part of a buildings envelope shall have insulation that shall retain its thermal properties under moise conditions and be installed

  1. for climatic zones 1 and 2, with a partially or completely unenclosed exterior perimeter, and shall achieve a total R-Value of 1,5,
  2. for climatic zones 3,4 and 6, with a partially or completely unenclosed exterior perimeter, and shall achieve a total R-value of 1,0, and
  3. with an in-slab floor heating system, and shall be insulated around the verticle edge of its perimeter and underneath the slab with insulation having a minimum R-Value of not less than 1,0.