Prefabrication experiments - 268 - Connectors - 09 - Sip Panel Joinery

 

Stressed skin panels, either stud-framed or laminated with an insulated core, were developed through research at the beginning of the 20^th century. They are a successful segment of industrialized building construction. The flat-packed panels used for walls, floors or roofs can be assembled in simple box frame configurations. Three most common forms are: wood frame and skin, skin and core, or composite materials. Every type of panel used as a shell component integrates a loadbearing layer, an insulating layer and in some cases a protective waterproof layer. Even with the important structural and insulating properties of each dimensionally coordinated panel, total performance hinges on the weathertightness and accuracy of the connecting joinery. Particularly for structural insulating panels or Sips, weathertight connections are essential for reducing heat loss and maintaining structural integrity. 

 

Systems are designed to achieve an uninterrupted insulating core by using a type of tongue and groove assembly which overlays a portion of insulation between two juxtaposes panels.  Openings for windows and doors can be milled in the factory. Panels arrive on site to be assembled as the large-scale pieces of a 3d puzzle. With the exceptions of greater assembly accuracy and more stringent dimensional tolerance this type of building panel has not really changed since the beginning of the twentieth century. 

 

Murus is an American company producing a SIP panel which in all respects seems like a fairly standard panel. However, to increase both precision, weathertightness and structural robustness, an interlocking cam connector has been patented and included in the proprietary panel. The hardware is in the panel's core and once two panels are juxtaposed aligned and put together, the connector can be rotated locking the panels in place from the outside of the panel with a key-like locking device. 

 

The panels are available in modular sizes and thicknesses with optional composite layering materials from oriented strand board, to plywood. Although not marketed to be disassembled and reused, it is easy to imagine this type of panel, assembled, locked, unlocked and disassembled to be reused.  Depending on the composite assembly specified, a 150 mm panel could range from a R value of 23 - 28. This value is uninterrupted by studs as would be the case for traditional timber framing.

Murus SIP panels with a joint connector