Polystyrene insulation is a kind of foam insulation that is used in both residential and commercial buildings. Polystyrene insulation is very rigid, unlike other fluffier insulating materials. As an insulator, it can withstand extremes in temperature and can also reduce noise. Unlike other insulation materials, it is waterproof and has a very long lifespan. All of these things make polystyrene insulation stand out as an exceptionally good product and it popular within the building industry.

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Insulation Made From Polystyrene

Polystyrene is a material with consistently small, closed cells and a smooth skin texture which make the material suitable for a wide range of demanding insulating applications. The types on polystyrene insulation include Expanded polystyrene (EPS), Extruded polystyrene (XPS) Compressible (shrinkable) EPS, and Insulated Plasterboard EPS.

Polystyrene Insulation can be applied to a range of applications including:

  • Basements and walls
  • Masonry cavity walls
  • Ground bearing floors
  • Suspended concrete floors
  • Separating floors
  • Underfloor heating system
  • Exposed soffit
  • Pitched roofs
  • Green/paved roofs
  • Floor insulation below the concrete slab

How is extruded polystyrene made?

Extruded polystyrene is made by mixing polystyrene pellets with various ingredients to liquefy them.  A blowing agent is injected into the mixture to form gas bubbles. The foaming liquid is forced through the shaping die and, when cooled, it produces a closed cell foam that is rigid and water resistant.

Expanded polystyrene is made from expandable polystyrene, which is a rigid cellular plastic containing an expansion agent. The raw material is heated in special machines called pre-expanders with steam at temperatures of between 80-100C. The density of the material falls from some 630kg/m3 to values of between 10 and 35kg/m3. During this process of pre-expansion, the raw materials compact beads turn into cellular plastic beads with small closed cells that hold air in their interior.

On cooling, the recently expanded particles form a vacuum in their interior, and this is compensated for by air diffusion during its intermediate maturing in aerated silos. The beads are dried at the same time. This is how the beads achieve greater mechanical elasticity and improve expansion capacity. Then the stabilised pre-expanded beads are transported to moulds where they are again subjected to steam so that the beads bind together. In this way moulded shapes or large blocks are obtained. They are later sectioned to the required shape like boards, panels, cylinders etc.

Extruded polystyrene is slightly denser and therefore slightly stronger in compression than expanded polystyrene however it has a lower thermal conductivity. It has a closed cell structure with very low water absorption and vapour transmission properties. It can withstand continuous temperatures up to 75 degrees C and can be easily worked with normal hand tools or no tools at all.

Benefits of Polystyrene Insulation

  • Low thermal conductivity
  • Lightweight and easy of handle and install
  • Polystyrene is one of the lightest insulating materials.
  • Has excellent mechanical properties making it good choice for load-bearing roof insulation, sub-pavement flooring, roadbuilding, as load-bearing insulation.
  • Low water absorption
  • Creates a more temperature-controlled environment
  • unaffected by damp, humidity, or moisture.
  • Chemical resistance – polystyrene is compatible with most other materials used in construction including cements, plasters, etc.
  • When installed correctly the material will last as long as the building itself.
  • Saves money on energy bills.
  • Resistant to corrosion.
How is polystyrene Insulation installed?

Extruded Polystyrene can be cut by measuring the board to size, marking, and then cutting with a sharp knife.

For ceiling application between joists the boards can be cut to size and pushed firmly in between the Joists. Ensure any boards joining are tightly butted together with no air gaps. The board should be cut 10mm wider than the exact fit to ensure a tight fit. Plastic reinforcing clips will need to be installed if the fit is not tight. Once the boards are in place the clips can simply be stapled to the joists.

Finishings can be applied one the polystyrene has been installed such as plasterboard or other insulation materials to be installed around pipes etc. Other methods of applications should be applied depending on where the polystyrene insulation is being installed such as floors or walls.

Polystyrene Insulation Products
Kay-Metzeler EPS70

Kay Metzeler is an EPS70 expanded polystyrene insulation board ideal for floor and wall insulation, Kay-Metzeler EPS70 provide a long-lasting thermal solution. It is a simple and cost-effective form of insulation that holds exceptional compressive strength.

  • 2400mm x 1200mm
  • Thicknesses, 25mm – 100mm
  • Thermal Conductivity 0.038W/mK
  • Expanded Polystyrene
Kingspan Greenguard

Kingspan GreenGuard is a high-performance rigid insulation board made up of extruded polystyrene with green facings designed for exterior insulation including the insulation of inverted roofs, basements, car park decks, and heavy-duty commercial, industrial, and cold store flooring.

  • GG300, GG500, GG700
  • 1250mm x 600mm
  • Thicknesses, 30mm – 150mm
  • Thermal Conductivity: 0.034W/mK, 0.036W/mK
  • Extruded Polystyrene

Polystyrene Insulation FAQs

Is polystyrene good for insulation?

In its expanded form, polystyrene has low thermal conductivity which makes it a great insulating material. Polystyrene foam contains a lot of small pockets of air within its structure, and this is an important key to its insulating properties.

Is polystyrene the same as Styrofoam?

Basically yes! The foam that you formerly knew as Styrofoam is actually expanded polystyrene foam or EPS. This material is made from polystyrene, a plastic that's often used to make insulations materials as well as clear products like food packaging or lab equipment.

Is polystyrene better than PIR?

In comparison to other insulation materials like mineral wool or the widely used Polystyrene foam rigid foam PIR term insulation boards provide a much more effective insulation value. PIR is a better insulator that Polystyrene however this depending on the placement and method of applications. Always consult a building professional.

Is polystyrene a good insulator of cold?

Extruded polystyrene insulation is excellent for use in extremely cold areas such as walk-in coolers and freezers. Polystyrene has many characteristics that prove it to be the best insulation material for walk-ins. Polystyrene is less water vapor absorbent; therefore, water vapor does not infiltrate through the material as quickly or easily as it does other insulating materials making it the ideal product for damp, cold, and wet environments.