SIPs (structural insulated panels)

These are one of the fastest growing alternatives to mainstrem timber-frame and brick-and-block construction methods.  They are made of engineered wood-based sheets, called oriented strand boards (OSBs), or cement particle board (CPB).  Two sheets are sandwiched together with a rigid middle layer or polyurethane insulation to make a solid and very strong construction.

The panels are dressed internally with a vapour-controlling membrane and plasterboard; externally they can be dressed with brick, timber etc.  SIPs can be used for walls, floor and roofs on a timber frame; their large size gives them thermal and sound insulation values that meet Building Regulations. 

SIPs building is sometimes referred to as timber frame without the timber.  Like panelised timber frame, it works on the idea of building up wall and roof panels on flat surfaces and then hoisting them into position, in contrast with masonry build systems which build walls up in situ. 

Where SIPs differ from timber frame is that they gain their strength not from any timber skeleton but from the rigidity of the panels themselves.  SIPs panels are essentially a sandwich; the filling is a solid thickness insulation and the outsides are made of rigid building boards such as plywood or orientated strand board (OSB).  These layers are bonded together which has the effect of making the panels extremely robust.  A decent builder will additionally ensure that where the panels meet is also properly insulated (to allow drafts in the joins).

The advantages are that you can create a structure with superb insulation levels, few cold bridges and excellent airtightness levels.  If installed properly, they also have the potential for faster construction speeds than timber frame.  The panelised roof elements lend themselves to building rooms in the roof, in a simpler and quicker manner than traditional methods.