![]() Under axial loads, the sheathing responds similarly to a slender column, and the foam core acts as continuous bracing preventing the panels from buckling. SIPs behave similarly to a wide flange steel column in that the foam core acts as the web and the sheathing responds as the flanges. ![]() Fundamentals Structural Design and Construction * Most SIP manufacturers use a 0.95 minimum density. **Not as hazardous as most brominated flame retardants, but health and environmental concerns still exist.Ĭompressive Strength 10% deformation (psi) *HBCD: hexabromocyclododecane - a brominated fire retardant classified by the European Union (REACH program) as persistant, bioaccumulative, and toxic (PBT). Most expensive harder to modify thickness limitations creep availability produced with chlorinated phosphate flame retardants** Highest R-value/inch strength, water resistant Least expensive thickness options are only limited by the foam manufacturer availability fastest to modify in field most benign blowing agent Resistant to mold and termites pre-primed materials available Must be galvanized or stainless steel not load bearingĪvailability price limited panel size subject to mold and reduced structural capacity if exposed to moisture for a prolonged period of time not fire resistant must be treated for termitesĪvailability weight testing limited panel sizeĪvailability testing limited panel size Reistant to mold can be load-bearing very light unlimited lengths when made from coil stock Subject to mold and a reduction in structural capacity if exposed to moisture not fire resistant must be treated for termites difficult substrate for most common joint tapes Load bearing readily available tested large panel size up to 8' x 24' Table 1: Sheathing Type Chart Sheathing Type The following tables outline the benefits and drawbacks of the most common sheathing and foam types. The type of SIPs selected depends upon the building type and site conditions. ![]() Other sheathing materials include: sheet metal, plywood, fiber-cement siding, magnesium-oxide board, fiberglass mat gypsum sheathing, and composite structural siding panels.Įach sheathing material and foam type has its benefits and drawbacks. The most common sheathing boards are oriented strand boards (OSB). ![]() With PUR and PIR, the liquid foam is injected and cured under high pressure. With EPS and XPS foam, the assembly is pressure laminated together. The foam core is generally one of the following: expanded polystyrene (EPS), extruded polystyrene (XPS), and polyurethane foam (PUR). Structural insulated panels are composed of an insulated foam core between two rigid board sheathing materials. Construction costs associated with SIPs are comparable to more conventional building methods when savings associated with labor costs, material waste, and energy efficiency are considered. SIPs provide a continuous air and vapor barrier as well as increased R-value when compared to traditional construction. Today, SIPs are prefabricated building components for use as walls, floors, roofs, and foundations. Dow created the first foam core SIPs which were being mass-produced by the 1960's. Frank Lloyd Wright used a form of structural insulated panels in the Usonian homes built in the 1930's and 1940's. These initial panels were used to build test homes that were disassembled and tested after thirty years to reveal that the panels retained their initial strength values. The Laboratory's prototype panels consisted of framing members, plywood and hardboard sheathing, and insulation. The Forest Products Laboratory in Madison, Wisconsin introduced the idea of what is now known as Structural Insulated Panels (SIPs) in 1935. Photo Credit: Steven Schaefer Associates, Inc. Figure 1: Example of SIPs used as infill with a structural steel frame, Silvis School, Illinois.
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