Extruded Polystyrene (XPS)

Extruded polystyrene insulation is manufactured through a plastic extrusion process. A foaming agent is added to the molten polystyrene mass after which the mass is pressed (extruded). After material has cooled the obtained product forms porous, closed cell foam with improved water resistance, high compressive strength and greater thermal performance than of standard EPS polystyrene board.

Extruded polystyrene is more than a simple lightweight insulant. The inherent mechanical strength of the product means that a building element or item fabricated with XPS can withstand a wide range of loading situations. Whether subjected to standard domestic loads or heavy industrial loads, in floors, roofs or in panels, XPS is the ideal solution.

Extruded polystyrene boards are almost 100% closed cell and as such are unaffected by moisture. Apart from non-absorbent properties XPS offers increased compressive strength which allows the product to be used for thermal insulation and damp proofing in difficult conditions in areas such as:

• parts of the building situated under ground level: foundations, basements
• terraces
• green roofs exposed to foot traffic
• inverted flat roofs
• floors exposed to heavy loads
• car park decks

Depending on type extruded polystyrene boards come with a variety of surface finishes:

• Rough or smooth
• Surface with drainage channels
• Extruded surface to increase render adhesion
• Surface finished with geotextile layer and modified cement mortar

Boards can be found with straight or bevelled edges (tongue and groove or overlapped edge)

Classification of extruded polystyrene insulation (XPS)

Similarly to EPS, extruded polystyrene comes in a range of thicknesses and can be classified according to its vertical compressive strength measured at 10 percent deformation or yield.

Insulation Cart offers extruded polystyrene (XPS) from Cellecta manufacturer who classifies their products with the following codes:

• Yelofoam X2i – XPS polystyrene board with compressive strength of 250-300 kPa depending on thickness
• Yelofoam X3i - XPS polystyrene board with compressive strength of 350 kPa
• Yelofoam X4L - XPS polystyrene board with compressive strength of 480 kPa

The advantages of using extruded polystyrene (XPS) boards:

• XPS boards are unaffected by moisture and can be used in areas where thermal insulation is exposed to direct contact with water; whether laying XPS boards in a floor (where there is often some standing water) or in a protected membrane roof system (where the insulation is exposed to water) the user can be confident extruded polystyrene will perform as stated

• extruded polystyrene offers better thermal performance than standard EPS (lower thermal conductivity)

• extruded polystyrene boards are tougher/stronger than EPS (higher compressive strength) and offer great dimensional stability
• XPS boards are lightweight which ensures easer transport to the building site and installation
• XPS boards are easy to cut and shape even with the use of a kitchen knife. Surfaces of the boards can be smoothed with a sand paper. In comparison with EPS, XPS polystyrene produces less dust during processing
• XPS insulation is safe to handle and has no adverse effect on health
• XPS insulation can be installed during any season of the year regardless of humidity and temperature

Factors to be considered when choosing extruded polystyrene (XPS) products:

• It is essential to choose the right product depending on its application
• For insulation of foundation walls, terraces, basements it is recommended to use grooved boards with a geotextile finish
• Whenever maintaining a smooth surface of the insulation layer and preventing thermal bridges is of prime concern, boards with tongue and groove or overlapping edges should be used