- What are SIPs?
- How much faster can I build with SIPs?
- How much money can I save with SIPs?
- How green are SIPs?
- How strong are SIPs?
- How do I properly size HVAC equipment?
- How important is ventilation?
- How do SIPs improve indoor air quality?
- How do SIPs react to Fire?
- Are SIPs compatible with other building systems?
- What considerations do you need to take into account when building with SIPs vs. conventional framing?
- Can SIPs be modified on site?
- How are electrical wiring and fixtures installed?
- Are SIPs susceptible to insects?
- Can SIPs be replaced or repaired if damaged?
- Do roofing manufacturers warranty asphalt shingles over SIP roofs?
- Does a building with a SIP roof need to be ventilated?
- How much do SIPs cost?
- Are SIPs accepted by building codes?
- How do I attach siding or other exterior claddings to SIPs?
- What is shingle ridging? Does shingle ridging occur in SIP buildings?
- What is the R-value of SIPs?
- How are SIPs supported? Are there studs in the panels?
- Can recessed lights be used in SIPs?
- Do SIPs block sound transmission?
- Are vapor barriers required in SIP buildings?
- Can plumbing be installed in SIPs?
- Can kitchen cabinets be attached to SIPs?
- Are SIPs susceptible to mold and mildew?
- I want to build a SIP home. What is the first step?
- How does the SIP design and fabrication process work?
- What is the learning curve for SIP installation?
- Where can I learn more about SIPs?
The structural characteristics of SIPs are similar to that of a steel I-beam. The OSB skins act as the flange of the I-beam, while the rigid foam core provides the web. This design gives SIPs an advantage when handling in-plane compressive loads.
SIPs can be engineered for most applications. Detailed information on the structural performance of SIPs is available from SIPA member manufacturers.
Like all wood frame buildings, SIPs present a manageable fire risk when their construction meets the fire precautions listed in the building code. Residential codes typically require the application of a 15-minute fire-resistant thermal barrier on the interior for all residential structures, accomplished by applying 1/2-in. thick gypsum board or a material of equivalent thermal performance.
Light commercial or multi-use buildings of Type V Fire Rated construction often require a one-hour fire rating and/or sprinkler systems. Many SIP manufacturers can provide tested assemblies for both walls and roofs that meet the one-hour fire resistance tests outlined in ASTM E 119. Check with your local manufacturer for specific assemblies.
Some roofing manufacturers warranty asphalt shingles over unvented SIP roofs, while others void their warranty because of higher shingle temperatures. Research conducted by Building Science Corporation reveals that although asphalt shingle temperatures increase slightly (2 – 3 degrees F) in an unvented roof assembly, the color of the shingles and the roof orientation have a much more profound impact on the durability of shingles. According to the Builder’s Guide to Structural Insulated Panels (SIPs) published by Building Science Corporation, the typical reduction of shingle life over an unvented SIP roof assembly is between one and two years.
Builders seeking to comply with roofing manufacturer warranties can choose from a variety of more durable, non-asphalt roofing materials or provide a venting space between the SIP roof panels and the roofing material (known as a cold roof).
The area inside a SIP building envelope is considered conditioned space and will be ventilated by the building’s HVAC system. There is no need to provide a vented attic beneath a SIP roof, and doing so would compromise the conditioned space of the building.
Research conducted by Building Science Corporation on test homes in hot climates demonstrates that including the attic in the conditioned space allowed for more energy-efficient space conditioning and less probability of moisture related issues. [Rudd, Armin and Joseph Lstiburek. Vented and Sealed Attics in Hot Climates. Building Science Press, 1998]
Some building science experts recommend venting the roof by providing an air space between the SIP roof panels and the roofing material (known as a “cold roof”). This practice is not a requirement for SIP buildings, but an extra measure to improve the durability and moisture resistance of the building.
Pricing information can be obtained by contacting any of SIPA’s Manufacturer or Dealer/Distributor members. However, the material price does not reflect the labor savings capable with SIP construction.
A study conducted by the R.S. Means shows that building with SIPs can reduce framing labor by as much as 55 percent over conventional wood framing. Builders can also expect decreased jobsite waste disposal costs and savings on HVAC equipment. When all these factors are considered, building with SIPs is often less expensive than other building systems.
SIP construction is recognized by the International Code Council body of building codes, which are used by most jurisdictions in the U.S.
For residential buildings, specific construction practices for SIP wall systems are included in Section R614 of the 2009 International Residential Code. For applications beyond the scope of Section R614, the building inspector will typically require a licensed engineer or architect to approve the building plans prior to construction. An engineer’s approval is always required in high wind areas, high seismic zones and commercial buildings.
Builders can contact a licensed design professional by searching SIPA’s Membership Directory.
Builders should consult the siding manufacturer’s installation instructions for how to attach their product to SIPs. Because SIPs use very little solid lumber, an increased fastening schedule is often required when attaching exterior cladding.
If the siding manufacturer does not offer recommendations for attaching their product to SIPs, a licensed architect or engineer can calculate the appropriate fastener frequency by obtaining fastener pullout capacities from the SIP manufacturer.
It is also important that proper moisture management procedures be followed when applying any type of cladding to SIPs. The Builder’s Guide to Structural Insulated Panels (SIPs) provides details for attaching various types of cladding materials. With the exception of metal and vinyl siding, the Builder’s Guide recommends that all claddings be installed with a drainage gap between the cladding and the weather resistant barrier in climates that average more than 20 inches of annual rainfall.
Shingle ridging is a bulging of asphalt roofing material that occurs along the joints of engineered wood panels used in roof applications. This rare phenomenon is caused by changing moisture content in the roof sheathing and occurs in traditional truss-framed roof assemblies as well as SIP roof assemblies.
The ridges caused by the expansion of SIP roof panels may be an aesthetic blemish, but it does not affect the performance of the roofing or the SIP roof panels.Several assemblies that prevent shingle ridging are described in the Builder’s Guide to Structural Insulated Panels (SIPs). Specifying a cold roof, or simply over-sheathing the roof with an additional layer of OSB staggered over the panel joints, will eliminate the possibility of shingle ridging. Alternately, wood shingles, wood shakes, or a standing seam metal roof can be used in place of asphalt shingles
R-values for SIPs depend on the thickness of the SIP and the type of core material that is used. See SIPA’s R-value chart for the minimum R-values of commonly available SIPs.
Static R-values, like those included in the chart, rate the effectiveness of insulating material. However, they do not accurately describe how products perform in a real world setting. When fiberglass or other types of insulation are installed, they are installed around structural members made of wood or metal that have very poor insulating value. Field-installed insulation materials are also prone to installation imperfections.
The Department of Energy’s Oak Ridge National Laboratory has studied and tested the performance of entire wall assemblies in large sections. The resulting whole-wall R-value data reveals that a 4-inch SIP wall rated at R-14 outperformed a 2×6 wall with R-19 fiberglass insulation.
For most applications, SIPs are structurally self-sufficient. The structural characteristics of SIPs are similar to that of a steel I-Beam. The OSB skins act as the flange of the I-beam, while the rigid foam core provides the web. This design is extremely strong and eliminates the need for additional framing.
In cases where a point load from a beam or header requires additional support, a double dimensional lumber spline or engineered wood spline is field installed at in-plane panel connections.
SIPs are also used as curtain walls for steel frame or timber frame structures. In large commercial applications SIPs can minimize the amount of structural support needed and reduce material costs.
In roof applications, SIPs rely on beams and purlins for support. SIPs can span long distances, allowing a minimal amount of structural supports to be used.
The sound resistance of a SIP wall depends on the thickness of the gypsum drywall applied, the exterior finish applied and the thickness of the insulating foam core that is used. SIPs are especially effective at blocking high frequency noise and most homeowners notice the quiet comfort of a SIP home. However, low frequency sounds are not as effectively stopped by a SIP building envelope.
For multifamily and commercial buildings, a universal sound transmission coefficient (STC) is used to specify the sound resistance of wall assemblies. Assemblies with a range of STC ratings are available, including options with a STC rating greater than 50 for party walls in multifamily buildings. SIP manufacturers can provide more information on these assemblies.
Plumbing should not be located in exterior SIP walls because of the possibility of condensation or supply lines freezing in cold climates. During the design phase of the project, all plumbing should be relocated to interior walls.
If plumbing must be located on an exterior wall, it is recommended that a surface chase be installed on the interior of the wall to conceal plumbing. Another option is to construct a small section of the wall using conventional wood framing that can be used to run plumbing. Plumbing penetrations such as DWV can be placed through SIPs if they are thoroughly sealed to prevent air infiltration.
It is recommended that the cabinet manufacturer provide instructions on how to attach their product to SIPs. Typically, an increased fastener schedule is required. Another option is to install plywood strips behind the cabinets to provide additional holding strength for fasteners.
If the cabinet manufacturer does not offer recommendations for attaching their product to SIPs, a licensed architect or engineer can calculate the appropriate fastener frequency by obtaining fastener pullout capacities from a SIP manufacturer.
An airtight SIP building envelope forms the basis of a successful mold control strategy. The extremely low levels of air infiltration in SIP buildings allow for incoming air to be provided in controlled amounts by air handling equipment. Proper dehumidification of incoming air following ASHRAE standards will create an environment where mold physically cannot grow.
In addition to creating an airtight structure, SIPs are solid and free of any cavities in the wall where moisture can condense and cause unseen mold growth.
For homeowners, the first step is to identify a quality builder who has experience with SIP construction. An experienced SIP builder will manage the plan conversion and review process. Search the SIPA Membership Directory to find an experienced SIP builder in your area.
For a builder looking to start their first SIP project, the first steps are to find a manufacturer or dealer/distributor to work with and explore some of the many educational resources available.
The construction of a SIP home or commercial building begins with the construction documents. Once the construction documents are in the hands of a SIP manufacturer, dealer/distributor, or design professional, they are converted to SIP shop drawings that give the dimensions of each individual panel.
The shop drawings are reviewed by the builder, engineer, the building owner, and other involved parties. Once the shop drawings are finalized, the SIPs are fabricated and shipped to the jobsite for installation.
For construction professionals competent in standard wood framing techniques, the task of learning SIPs is not difficult. The SIPA Registered Builder program offers both online and onsite training courses covering everything builders need to know about SIP installation.
Many SIP manufacturers and dealer/distributors also offer onsite technical assistance for builders that are new to SIP construction.
There are a number of resources on structural insulated panels:
Builders can participate in both online and hands-on SIP installation courses through the SIPA Registered Builder Program.
SIPA offers an AIA Continuing Education course for design professionals.
Browse the publications on the SIPA Online Store. Building with Structural Insulated Panels, by Michael Morley, and the Builder’s Guide to Structural Insulated Panels (SIPs), by Joe Lstiburek, are two popular books that contain a wealth of information.