What Are Insulated Sandwich Panels?

Insulated Sandwich Panels (ISP) have been used for commercial construction in Australia for the past 50 years. Insulated Sandwich Panels (ISP) are made when three separate elements are “sandwiched together” to form one structure, see Diagram 1. The combined properties of the high tensile and compressive strength of the outer steel skins and the high shear strength of the inner core leads to a building material which has a much longer spanning capacity and is lighter in weight than traditional building materials.

Diagram 1

The most common cores used in Insulated Sandwich Panel (ISP) construction are Expanded Polystyrene (EPS), Polyurethane Foam (PUR), Polyisocyanurate Foam (PIR) and Mineral Wool (MRF) or Rock Fibre.

  EPS Expanded Polystyrene PIR Polyisocyanurate  
EPS-FR Expanded Polystyrene Fire Resistant MRF Mineral Fibre
XPS Extruded Polystyrene SPS EPS Phenolic Hybird (Syntactic)

PUR panel has not been extensively manufactured or used in Australia.

EPS is manufactured from styrene monomer, using a polymerisation process which produces translucent spherical beads of polystyrene, about the size of sugar granules.  During this process a low boiling point hydrocarbon, usually pentane gas, is added to the material to assist expansion during subsequent processing.The flame retardant predominately used for expanded polystyrene is hexabromocyclododecane (HBCD). HBCD is added during the polymerisation process and is retained within the polymer matrix.

PIR panels are produced by foam in place as opposed to drop in manufacturing processors.

Advantages of Insulated Sandwich Panels

Significantly reduces the amount of energy required to keep buildings within a comfortable temperature range.
Light weight, low maintenance, recyclable and reusable.
Uses the non ozone depleting insulants.
Steel skins can be made with between 10-30% recycled material.
Reduces landfill over standard framed construction methods.
Provides continuous insulation that reduces or eliminates thermal bridging.
Provides a consistent level of insulation that is impervious to compression, water vapour, vermin and rot.
Reduces air-leakage/infiltration rates.
Significantly shortens construction time.
The perceived disadvantage of ISP has been its performance in fires. The most common criticisms of ISP in fire conditions relate to the delaminating of the outer skins exposing the core, the structural ability of the Panels to stay in place and not collapse during a fire and fire spreading within the Panel. There have been improvements over time to ISP and addition of fire retardants, metal fixings, not using plastic fixings, etc. The objective of the Code of Practice ("the CODE") is to bring all of these improvements, and others in further research and testing, together into one system and industry CODE.