Pick Your Filling
Structural insulated panels (SIPs) can be thought of as oversized ice cream sandwiches. The first thing SIP manufacturers do is select which type of insulation—or filling—the panel will have. The most common filling is expanded polystyrene, but SIPs can also use extruded polystyrene, polyurethane, and other materials. Different fillings have different performance properties—some are better insulators while others are more structurally sturdy. The panels can vary in thickness from around 3-1/2 inches up to 11-1/4 inches, and achieve insulation levels ranging from R-16 to R-49, respectively.
Apply the Glue
The outer layers of the ice cream sandwich are typically oriented strand board (OSB), though plywood, gypsum board, and fiber cement board are also common. Manufacturers use structural-grade adhesives to stick these outer pieces to the insulation. This often requires machines called roll coaters or bead applicators to brush or squeeze glue onto the layers. The machines apply glue from the bottom layer up, starting with a single sheet of OSB lying flat. The foam core is then placed into the adhesive, followed by another coating of glue on the foam core, and then the top layer of OSB is added.
Turn Up the Pressure
The adhesive has a tendency to expand, so in order for the panel components to stay together, manufacturers must press the entire sandwich together. This process varies: Some companies stack a pile of SIPs—anywhere from two to 20 of them—and compress them as a whole. Other manufacturers use a conveyer belt press that applies 4 to 6 pounds per square inch of pressure to each panel individually. After four to five minutes of pressure, the components are fully adhered.
Trim the Excess
Initially, SIPs are rectangular and range in size from 4 feet by 8 feet to 8 feet by 24 feet. In order for SIPs to be used efficiently in construction, they must be cut to custom shapes and sizes. Architects can work with SIP manufacturers to lay out and determine the precise configuration for each panel. To finish each SIP, manufacturers can add connectors, create joints, or close off the exposed edges with a thin strip of OSB, depending on where the particular panel will be placed in the building wall or roofing system.