Structural Insulated Panels (SIP)

Advanced Framing Techniques | Structural Insulated Panels (SIP) | Insulated Concrete Forms (ICF) | Adobe

Structural Insulated Panels are a widely used alternative construction material for homes. SIPs are panels made from a thick layer of foam (polystyrene or polyurethane) sandwiched between two layers of oriented strand boardSmall chips of wood are pressed together and embedded in phenolic glue to make a strong material that can replace plywood and is used for structural sheathing and subflooring. (OSB), plywood, or fiber cement. As an alternative to the foam core, SIPs are available with a core of agricultural fibers (such as wheat straw) that provides similar thermal and structural performance. The result is an engineered panel that provides structural framing, insulation, and exterior sheathing in a solid, one-piece component.

Panel manufacturers now use continuous lamination machines, which automate forming and cutting according to dimensions downloaded from digital floor plans. The panels will arrive precut, and can be rapidly assembled by students without extensive training. Using SIPs will allow you to quickly construct an exterior building envelope that is strong, airtight, and energy efficient.

Some manufacturers now offer special variations in SIP products, such as a high-end panel made with an injected polyurethane core, and vertical joint connectors featuring eccentric cam locks that draw the panels tightly together and assure proper alignment. Manufacturers can also produce curved walls or other customized architectural features.

FAST FACT: Oriented Strand Board (OSB) is a plywood-type engineered wood product made from renewable controlled growth wood.

SIPs in Practice

Structural Insulation Panels (SIPs). SOURCE: Energy Star Thermal Bypass Checklist For a 2,500 square foot home, one custom homebuilder in Arkansas (Stitt Energy Systems) estimates an additional $5,000 to $8,000 for materials. Labor savings are substantial however, and can tip the economic scales in favor of SIPs. For example, in areas of the country with high labor rates, installation costs for SIPs can be lower than conventional wall systems.

SIPs have:

• Manufactured wall panels 4' to 24' wide and 8' or 9' high, made in standard thicknesses of 4 1⁄2" to 6 1⁄2".
• Thicknesses of up to 12" for roof panels where greater R-valueA unit used to measure thermal resistance, derived from the ratio of the temperature difference across an insulator and the heat flux through it; the ability of the structure to hold internal temperature. The larger the number, the more effective the insulation. is needed.
• A core material of thicker panels usually corresponds to standard lumber dimensions, so board stock may be used for splines and plates. Panel lengths can vary to accommodate higher ceilings or roof spans up to 24'.

FAST FACT: The SIP exterior is ready to receive a finish, such as siding, stucco, or masonry. It requires no moisture sealant, just seal the seams, doors, and windows.

Implementation of Structural Insulated Panels (SIPs)Two sheets of oriented strand board with solid foam insulation sandwiched between them, used for roof, wall or floor structures and providing high insulation values while using less facilitating the use of less wood.

• Send your plans to an SIP manufacturer so it can produce a customized panel layout and working drawings.
• Have a structural engineer certify the design.
• Have the foundation in place before panels are delivered.
• If possible, use a forklift or have at least four people on site to unload the truck.
• Assembly can usually be done in one to two days.
• Use aerosol foam, gaskets, or other caulking materials for sealing SIPs.
• Bond the foam core to the stiff outer skins to create a web-and-flange structural strength (along the same principal as an I-beam) across the length and breadth of the panel. Insulation capacity is another advantage of SIPs.
• The foam core is typically held back from the edge to allow the panel to accept 2 x 4 top and bottom plates. Alternatively, placing header sections between full-length wall panels may create rough openings for doors.
• Window openings can be made in a similar fashion with the addition of a base panel. Dimensional lumber usually frames out rough openings.
• For wider openings, headers with greater load bearing capacity may be needed. Insulated headers using sandwiched foam have been specially designed to work in conjunction with SIPs.
• Properly seal joints.
• Consult a structural engineer to specify required headers and connections.

Benefits of Structural Insulated Panels

• With the capacity to handle axial, bending, racking, and shear loads, properly designed and assembled SIPs not only replace conventional framing, but will withstand high wind and great seismic forces.
• SIPs provide better overall air tightness than conventionally framed walls.
• SIPs panel systems offer a dense, uniform, and continuous air barrier with few thermal bridges, and no opportunity for internal convection.
• SIPs generally have higher R-values than similarly sized framed walls, improving thermal performance.
• Operational energy costs are typically low.
• Labor time is reduced due to ease of installation.
• Uses at least 50 percent less framing lumber.
• Requires less room at building site (less site disturbance).
• SIPs contribute less construction waste to landfills due to their customized sizing.

Challenges of Structural Insulated Panels

• If the inhabitants wish to remodel, they may have to hire a design professional.
• Producing and engineering the SIPs may increase initial costs.
• It is difficult to determine the exact increase in initial costs, but
• panels usually cost more than stick frames do.

Case Study

YouthBuild AmeriCorps Rebuilds Gulfport, Mississippi, with SIPs

In the fall of 2005, YouthBuild USA and the YouthBuild movement of hundreds of local programs across the nation pledged to build upon their experience, infrastructure, and dedication to help respond to the economic and social disaster wrought by Hurricane Katrina. Through this dedication and the support of The Home Depot and the Corporation for National and Community Service, the YouthBuild AmeriCorps Katrina Rebuilding Project was born.

This project has engaged 385 YouthBuild AmeriCorps graduates and students who have used the construction skills and community service they learned from their programs to build 140 units of housing in North Gulfport, Mississippi, a predominately low-income community that was destroyed by the hurricane. A special AmeriCorps program of 35 YouthBuild graduates has been in Gulfport for one year, dedicating their full time to restoring this devastated community; they have been joined by rotating crews of 35 to 45 current AmeriCorps members approximately every month from YouthBuild programs nationwide.

What makes this project an exciting step forward in the trend towards building green in YouthBuild is the opportunity it presents to not only offer affordable housing to the people of Gulfport, but also to offer environmentally conscious housing while educating YouthBuild graduates and students on green building applications and materials.

The use of the SIPs played a pivotal role in enabling the YouthBuild AmeriCorps Katrina Rebuilding Project to construct homes that were at once sound, affordable, and green. ThermaSAVE is a pre-assembled structural insulated panel made of expanded polystyrene and concrete, and eliminates the need for conventional wood framing and insulation. The environmental benefits are: it is nonhazardous (versus fiberglass insulation); it reduces construction waste (compared to traditional wood framed construction); it is a terrific insulator and substantially reduces energy consumption from heating and cooling; and it is highly resistant to mold, pests (such as termites), and fire and natural disasters—SIPs are structurally sound to survive severe storms, hurricanes, and earthquakes­—and therefore minimizes additional resources needed for repair and reconstruction. SIPs can be used to construct foundation or basement wall, even below grade; floors spanning up to 16 feet between supports, load-bearing walls up to four stories. Lastly, many SIPs, such as ThermaSave, are certified by the International Code Council (ICC).

To learn more about the YouthBuild AmeriCorps Katrina Rebuilding Project and its application of ThermaSAVE and other green building materials, contact Tony Frazier at tfrazier@youthbuild.org.