Structural insulated panels, or SIP’s, are prefabricated building materials used to build homes instead of conventional wood framing. Because it is a relatively new construction method, contractors must undergo specialized training before they can use SIP’s to construct buildings. SIP’s meet building code requirements and are subject to third party testing. They usually come with a 10-year warranty.
SIP’s are exterior structural elements and provide the structural support for the house. Buildings constructed with SIP’s are considered to be twice as strong as those constructed with traditional wood framing. SIP’s are used to construct walls, roofs, and floors in houses and in some commercial buildings.
SIP’s are composed of an inner core layer of rigid foam insulation, either expanded polystyrene (EPS), or polyisocyanurate, and two outer layers typically consisting of oriented strand board, plywood, or wafer board. Together these three layers form a very strong building material that is structurally similar to an I-beam. The two outside layers provide the structural support, and the inner core joins them together.
Because they are solid, channels are built into the SIP’s replacing the conduits typically used for electrical wiring in wood frame construction. Plumbing is generally not affected.
Sizes and Finishes
SIP’S are pre-fabricated and pre-cut by the manufacturer. Rough openings for doors and windows are also pre-cut. SIP’s are available with interior finishes laminated onto the interior face of the panel such as gypsum wallboard or a wood veneer such as pine, cedar, oak, or cherry.
The panel thickness ranges from 4 1/2” (standard wall thickness) up to 12 1/4” Panel sizes range from 4’ x 8’ up to 9’ x 28’. Because of the rigid structure, SIP’s are available in larger than normal sizes. Custom sizes also are available.
What are the Advantages?
1. The costs of using SIP’s are similar to those of traditional wood frame construction. The materials are more expensive, but labor costs are less because SIP’s are pre-fabricated by the manufacturer. In addition, the manufacturer supplies all the parts associated with SIP’s such as adhesives and fasteners, and other types of accessories.
2. They can be used to build over basements or slab foundations.
3. Heat and cooling costs are less in houses constructed with SIP’s. Because SIP’s are similar to a solid panel, there are no air spaces. Insulation R-values are also higher than for traditional wood frame construction packed with fiberglass insulation. Therefore, smaller heating and cooling units can be used, resulting in a house that is almost 50% more energy efficient.
4. More living space is created when using SIP’s for two reasons. First, there are no interior structural members, which allows for an open and flexible floor plan. Second, wall thickness, including insulation is the same width as a standard wall. To create an equivalent R-value in wood frame construction, a thicker layer of insulation - and thicker walls - would be necessary.
5. Siding can be applied directly to the SIP. No vapor barrier is required.
6. Kitchen and bathroom cabinets can hang directly on SIP’s before installing drywall.
7. Drywall can be glued or nailed directly onto the SIP.
8. Homes constructed with SIP’s are able to withstand hurricanes and earthquakes better than conventional wood framed houses.
