SIP Structural Performance
Technical Details / Data
Energy efficient Structural insulated panels (SIPs) are prefabricated, high performance, lightweight, building panels that can be used in walls and roofs for residential and commercial buildings. A SIP consists of two high density facings, typically Orientated Strand Board (OSB) which are auto-adhesively bonded by the low density, cellular foam core.
The panels are typically made by sandwiching a core of rigid foam polyurethane (PUR) insulation which is auto-adhesively bonded to the two structural skins (usually OSB) via an injection process. A strong, structural bond between the three layers is essential to the load bearing ability of the SIP so that high loads can be transmitted by the relatively light elements, thereby reducing the use of internal studding. SIP walls can bear considerable vertical and horizontal loads with reduced internal studding. The load carried by the SIP is transferred to ground by the OSB skins, held in position by the fully bonded insulation core.
Manufacture of SIPS
SIPs are manufactured under closely controlled factory conditions and can be custom designed for each application. The result is a building system that is extremely strong, energy efficient and cost effective. Strict quality control procedures are operated by SIPCO in the manufacture of SIPS to ensure quality and consistency of panel performance.
There are two fundamental applications for SIPS; full structural and infill walling for a concrete, steel or engineered timber frame. In all cases the SIP will be engineered for load bearing capability, racking resistance and wind loading in accordance with the test results contained within the SIPCO BBA certification.
Structural Strength and Testing Procedures
SIPCO panels have been subjected to a number of testing procedures. These include loading the panels with a uniformly distributed load (UDL) to measure strength and deflection between two supports, axial loads centrally and eccentrically placed, racking loads and shear and bending loads on the panel joints. The strength of the joints between the individual panels is such that panels can be used to span over openings and be supported by the panels each side. It is easy to incorporate additional timber to support localised concentration of loading. Routinely this is done at the joints in the panels. However, with careful detailing, much of this can be avoided.
Tests have shown that the panels have a very high ultimate bending strength. Deflection, calculated as described in our Design Guide, is the governing criterion in design. This increases user confidence knowing that safe working loads are well in excess of standard deflection limits.
Axial loading tests on panels 100mm thick, 2.4m in height and 2.4m in width were seen to fail at a load of 440kN/m. Using a factor of safety of 2.0 it is seen that panels will comfortably support a vertical load of 90 kN/m. These loads are well in excess of the average foundation loading from a typical two-storey house of traditional construction.
Additional information can be found within the Structural Timber Association SIPS Technical Bulletin 1 and SIPS Pocket Guide.