Home > FAQs
- What are SIPs?
- What’s the difference in “stress skin,” “foam core sandwich,” and “structural insulated” panels?
- Are SIPs as strong as conventional construction?
- Is SIP construction more expensive?
- How much time can be saved building with structural insulated panels?
- How much labor can be saved with structural insulated panels?
- How much money can be saved with structural insulated panels?
- How much do SIPs cost?
- How are SIPs green?
- What is the R-value of Murus SIPs?
- Are these “aged” R-values?
- Why is OSB used instead of plywood?
- How strong is the OSB used in SIPs?
- Does the OSB contain any Urea formaldehyde?
- Does the OSB contain any Phenol formaldehyde?
- Does the polyurethane foam contain formaldehyde?
- Does the EPS foam contain formaldehyde?
- Does the NEOPOR EPS foam contain formaldehyde?
- Is there any danger of the foam off-gassing?
- Will the foam degrade over time?
- How is Murus polyurethane different than other manufacturers’ foam?
- Which foam type is better - Murus polyurethane, EPS, or NEOPOR?
- Have SIPs been thoroughly tested and do they have building code acceptance?
- What does a Class 1 Fire Resistance Rating mean?
- What other panel skin materials are available?
- What style of house can be built with SIPs?
- How are Murus SIPs installed?
- What supports the SIPs?
- Who handles the installation of the SIP shell?
- Is there a learning curve for SIP installation?
- Why should I consider having my order factory pre-cut?
- What equipment do I need to modify the panels?
- What supplies will I need to install the panels (i.e., supplies not included with the Murus panels)?
- What foundation system should I use?
- What types of siding and exterior finishes may be used?
- Do you install the 2x lumber at the factory?
- How is wiring accomplished in Murus SIPs?
- How is plumbing accomplished in Murus SIPs?
- Does a SIP structure require special HVAC consideration?
- What can be done to insure healthy indoor air quality of a SIP structure?
- Are there any special considerations when building with SIPs?
- Does a SIP roof need to be vented?
- Are vapor barriers necessary in SIP buildings?
- How well do SIPs block sound transmission?
- Can SIPs be integrated with other types of building systems?
- How are shingles or metal roof coverings applied to Murus roof SIPs?
- What is shingle ridging? Does shingle ridging occur in SIP buildings?
- Can SIPs be cut on the jobsite?
- Can recessed lights be installed in SIPs?
- How are kitchen cabinets and other wall elements mounted?
- What is the best way to protect Murus SIPs from insects?
- Are structural insulated panels susceptible to mold and mildew?
- Can damaged SIPs be repaired or replaced?
- How does Murus compare to other SIP manufacturers?
- What does the design and fabrication process entail?
- Can Murus design my home?
- Are span and load tables available for Murus SIPs?
- What information does Murus need in order to provide an estimate?
- Where should I send plans and documentation?
- What is the average lead time on an order?
- Are there special storage considerations for the panels once they’re on site?
- Once installed, how long can the SIPs remain exposed to the elements?
- Where can I learn more about structural insulated panels?
SIPs, or structural insulated panels, are a composite, high performance building panel for walls, roofs, and floors in residential and light commercial construction. SIPs have a core of rigid polyurethane, EPS, or NEOPOR EPS insulation that is sandwiched between two structurally rated skins of oriented strand board (OSB). SIPs provide continuous structural integrity and superior insulation in one component.
The terms “stress skin”, “foam core sandwich”, and “structural Insulated” panels (SIPs) all refer to the same product and are interchangeable. The industry terminology has standardized and the term “SIPs” is most often used. However, “stress skin panels” and “foam core sandwich” panels are still popular terms among timber frame professionals.
SIPs construction is actually stronger than conventional construction because of SIP’s composite construction. A SIP’s configuration can be likened to a steel I-beam in which the OSB skins act as the flanges and the foam core acts as the I-beam connective web that gives the composition cohesive strength and structural integrity. SIP structures have survived some of the most devastating natural disasters, including Hurricanes Andrew and Katrina, and test results show that SIPs out-perform conventional construction in strength and durability.
The initial, up-front cost of SIP construction or materials over conventional construction or materials is typically a bit more, depending in part on the complexity of the design. However, there are real savings in labor time, and in construction waste volume reduction. A recent study by Reid Construction Data for BASF shows that residential builders can reduce their framing labor needs by as much as 55% by using SIPs. And when complete, a SIP building envelope will continue to bring significant, welcome savings in heating and cooling energy use.
With an experienced SIP installation crew, the time savings over conventional construction can be significant. The separate steps of framing, insulating, and sheathing are eliminated thanks to the composite construction of SIPs. Having window and door openings factory pre-cut speeds the installation process even further, and virtually eliminates panel construction waste.
A great deal of the labor involved in traditional construction methods is eliminated when building with SIPs as a result of their composite construction. A SIP is framing, insulation, and sheathing in one prefabricated component. Once installed, SIPs are ready for interior and exterior finishing.
For a builder, savings come from decreased construction and labor costs. Additional savings can be attributed to reduced jobsite waste disposal and downsized HVAC equipment. For homeowners, savings come from significantly lower heating and cooling energy costs, and possible qualification for lower mortgage rates and tax incentives.
Pricing is determined based on the project - its complexity, the type and thickness of foam core required, and the square footage of panels needed. In order to determine a realistic, accurate cost, the standard procedure is to submit plans that include dimensions and elevations to Murus for a written estimate. While the resulting price may be slightly higher than conventional construction, the savings potential for building with SIPs should also be considered: labor, HVAC equipment, and jobsite waste disposal savings for the builder, and ongoing heating and cooling energy savings for the homeowner.
Murus SIPs are green in several respects. First, the high-performance SIP building envelope creates a highly energy efficient environment that reduces the demand for heating and cooling energy. Murus SIPs can potentially contribute to points under the LEED Rating System and the NAHB Green Home Building Guidelines. The foams in Murus Polyurethane and EPS SIPs contain no harmful blowing or expanding agents and do not pose a threat to the ozone layer. The OSB (oriented strand board) used in Murus SIPs is SFI (Sustainable Forestry Initiative) certified, assuring that the rapid-growth trees used to make the OSB are from well-managed forests and plantations. Factory production and pre-cutting of Murus SIPs virtually eliminate panel scrap waste at the jobsite.
System R-values range from R-15 thru R-52, depending upon the panel foam core type and the overall thickness of the panel.
OSB is more desirable for panel skins because it is available in large-format sizes up to 24’ in length. It is also flatter and more resistant to delamination.
The wood fibers are oriented in a way that gives the board more than adequate strength for satisfactory performance. The strength and integrity of the OSB is fully tested, documented, and structurally rated by the manufacturer and other agencies.
Structural wood products such as OSB are manufactured to meet the Voluntary Product Standard PS 2-04. The phenol formaldehyde used in bonding adhesives during board manufacture are reacted into stable bonds during pressing. The final products have such low phenol formaldehyde emission levels that they easily meet or exceed government standards which specify a 0.20 ppm emission limit, and are considered not to pose any health threat.
No. There is a trace quantity of off-gassing which is emitted by the blowing (or expanding) agent during the manufacturing process. Once the manufacturing and curing processes are complete, the foam is stable and inert.
The foam in Murus SIPs will not degrade over time if properly covered and protected with approved finish materials after installation.
The properties and characteristics of Murus Polyurethane are superior to Isocyanurate and Polyisocyanurate foams typically produced by board stock manufacturers and some other SIP manufacturers. Murus’s proprietary manufacturing method, Uniform Dispersion Molding (UDM) is key to creating Murus SIPs’ superior characteristics. Each panel is manufactured (molded) independently. Liquid foam is dispersed uniformly throughout the panel mold. The foam expands, exerting up to 14 psi of pressure which is contained by the mold. During the expansion and containment process, the foam permanently bonds to the panel skins. The spherical cells produced by the UDM method provide uniform foam density throughout the panel, thus giving the foam superior and uniform strength, unlike the elongated, rice-shaped cells typically produced through the faster running continuous lamination lines in the production of Isocyanurate and Polyisocyanurate foams.
No foam type is necessarily better than the other; rather, each foam type has unique properties and may offer advantages in certain instances. The primary differences between the three are the density and insulating characteristics of the foam. EPS foam density is a nominal 1 pound per cubic foot, NEOPOR EPS foam density is a nominal 1.15 pounds per cubic foot, and Polyurethane density is nominally 2.2 pounds per cubic foot. Therefore, a 4-1/2” thick EPS panel will yield an R-value of R-15; a 4-1/2” thick NEOPOR EPS panel will yield R-17, and a 4-1/2” thick PUR panel will yield R-27.
Yes, and yes.
Class 1 Fire Resistance Rating is given to materials that conform to test standards set by the American Society for Testing and Materials (ASTM E-84) for acceptable flame spread and smoke development for combustible construction materials. ASTM E-84 is a similar test to UL-723, NFPA 2255, or UBC 8-1. Testing is accomplished by suspending a sample of material in the tunnel of a horizontal test chamber. The material is exposed to gas flame on one end of the tunnel for 10 minutes. The flame progression on the material is compared to selected standards and calculations designed to produce a flame spread rating. Smoke from the fire in the tunnel is measured in the exhaust stack via a light beam to establish smoke developed ratings. There are three classes of acceptability for rigid foam used in construction: Class 3 is unacceptable, Class 2 is the minimum standard required for residential construction, and Class 1 is the best classification available. Murus SIP foam cores have a Class 1 Fire Resistance Rating.
Structurally rated oriented strand board (OSB) is typically the most common skin material. Other materials include plywood, cement board, pressure-treated plywood, and pine cladding.
Just about any style of house design can be built using SIPs. Most designs originally meant for conventional stick construction can be modified to incorporate SIP construction, as well.
In structural applications, SIPs are typically installed over a 2x plate that is attached to the sill or subfloor. The foam core is removed from between the skins to a depth comparable to the plate so the panel sits over the 2x and nails are driven through the skins into the 2x. Typically, a double 2x top plate is installed in the same manner. There are many variations on these procedures. The Murus Panel Installation Manual can provide detailed information.
In the majority of construction applications, SIPs need no additional support. When reinforcing support is required as in a point load under a beam or header, for example, corresponding dimensional lumber can be easily installed in the panel on the jobsite.
General contractors or builders are typically responsible for panel shell installation. Murus can provide contact information for professionals experienced in Murus SIP installation in most regions.
The transition from conventional stick framing to SIP installation should be easily accomplished by construction professionals. Onsite technical assistance is available if needed, but is typically not necessary.
There are several reasons. Murus uses state-of-the-art precision CNC (Computer Numerical Control) equipment to accurately cut your order according to the Panel Layout Drawing specifications. Factory pre-cutting markedly reduces installation time and virtually eliminates jobsite panel waste. Panel Layout drawings are included as part of the Panel Pre-cutting Service, and provide exact panel layout and placement specifications.
A Circular saw, panel router (for polyurethane), or a hot knife or foam scoop (for EPS and NEOPOR EPS). See SIP Tools page for more information.
Mostly common building materials will be required. Your Murus panel drawings will call out all 2x and engineered lumber. Beyond this, you will need construction adhesive, common nails and screws, and other usual construction material.
Any foundation system that can be used for conventional construction can be used for SIP construction. Whatever type of foundation system is employed, it is of utmost importance that it is straight, true, plumb, and square for a successful panel installation.
Virtually any type of siding may be applied to the exterior surface of a wall SIP. Some common materials include a variety of vinyl siding, aluminum siding, and kiln dried wood sidings to include clapboard, shiplap, board and batten, and shingles. Exterior finishes should always be installed in accordance with the manufacturer’s recommended installation instructions. When applying exterior finishes, a layer of house wrap or felt paper should first be applied over the SIPs. Masonry and fiber-reinforced stuccos can also be used if a ventilated air space is provided. Masonry materials such as brick veneer must not come in direct contact with the SIP. A vented air space between the veneer and SIPs, and weep holes in the masonry must be provided.
No. For the purpose of adding strength, 2x lumber should span the panel joints. Installing 2x lumber in the factory would result in no span between joints, thus defeating the purpose.
Electrical chase(s) are incorporated into the panels during the manufacturing process. The chases are typically at standard horizontal heights for outlets or counter top receptacles. Vertical chases can also be specified in EPS and NEOPOR EPS core SIPs. The majority of the wiring is accomplished during or after the panel installation. For more information, refer to the Murus Panel Installation Manual.
Most building codes do not recommend, or may prohibit, installation of plumbing or vent lines in exterior walls, so a little planning during the design phase will keep plumbing installation simple and no more difficult than in any other building type. Place plumbing in interior partition walls according to generally accepted building practices.
Because SIPs provide an airtight building envelope and exceptional insulating properties, it is important to incorporate properly sized HVAC equipment into a SIP structure. Fortunately, often less is more in this instance. Equipment that is the correct size for a stick-built structure may well be oversized for a SIP structure of comparable size and layout. Oversized equipment will run more frequently at less than optimum levels, reducing energy efficiency and increasing frequency of equipment maintenance. Consult with a knowledgeable HVAC contractor to determine the project’s specific air handling needs.
Indoor air quality has become a major health concern in homes and buildings that are built to meet or exceed today’s energy efficiency mandates. A structure that is properly built with SIPs can be very airtight, so most manufacturers, including Murus, require the inclusion of a mechanical ventilation system in the HVAC plan. Typically this is achieved through the use of a Heat Recovery Ventilator (HRV) or an Energy Recovery Ventilator (ERV). Most of the major HVAC system manufacturers now offer these units as do many smaller companies, so consult with your mechanical contractor. Read more: Mechanical Ventilation
Be sure to seal all joints and voids with spray foam. Sealing with spray foam insures a continuous envelope of insulation and an effective airtight barrier for optimum efficiency and performance.
Murus has always held that a “cold” roof, or ventilated roof on top of the panels, is the best application. Typically this is accomplished by first installing 15-pound roofing felt on the roof panels, then installing 1x or 2x lumber vertically from the eaves to the ridge. These “straps” are put on 16” or 24” centers and sheathing (OSB or plywood) is attached over strapping before the finish roofing material is applied. The eave is left open and the ridge is vented with a vent cap. See the Murus Installation Manual for more information.
No, vapor barriers are not typically necessary in SIP construction. When properly installed, SIPs provide an effective vapor barrier by themselves. Some state or local codes may require vapor barriers over SIPs; check with your local code official for requirements in your area.
How sound-resistant a structural insulated panel can be is dependent upon the thickness of the finish materials, such as drywall and/or exterior siding, and the thickness and type of foam core. Murus does not have STC (Sound Transmission Coefficient) testing on our products, but many of our clients attest to the quietness of their structures built with Murus SIPs.
SIPs integrate easily with most other types of building systems, such as ICFs, poured concrete, cinder blocks, roof trusses, and stick framing.
It depends upon which type of roof finish material will be used. Ultimately, installation details and technical information on the specific roofing product should be verified through the product manufacturer.
Shingles: Not all shingle manufacturers warrant shingles applied directly over an insulated deck or SIPs. Depending on your choice of manufacturer, an additional ventilated space may be required for warranty qualification. The preferred and recommended method of shingle installation is on an elevated, ventilated surface. Furring strips or strapping are screwed vertically over a layer of roofing felt to the exterior surface of the roof panel on 16” to 24” centers. A layer of sheathing material is applied on the strapping as the nail base for the shingles. This system requires both eave and ridge vents to vent the cavity and prevent condensation and heat buildup.
Metal: For metal roof applications, an additional layer of strapping, installed horizontally, can be used in lieu of the sheathing.
Visit the Murus Panel Installation Manual for more information.
Shingle ridging is the bulging of asphalt roofing material, such as shingles, above the joints of engineered wood panels used in roof applications. It is caused by moisture changes in the underlying sheathing and can occur in traditionally framed roof assemblies as well as SIP roof assemblies. Ridging does not affect the performance of the SIP roof and is strictly aesthetic. To eliminate the possibility of shingle ridging, an additional layer of OSB can be installed in a staggered pattern over the SIPs joints; a cold roof can be installed; or other-than asphalt materials can be used.
Yes. Panel-specific tools may be required. See SIP Tools page for more information.
No, because there is no ventilation or airspace in a SIP to dissipate the heat buildup from the fixture, which would create a fire hazard.
Kitchen cabinets and other wall elements can be mounted directly on the SIPs, or can be installed on plywood strips that have been applied to the SIPs. Check with the cabinet manufacturer for recommended fastener schedules specific to SIPs.
No matter what type of structure you are building, whether it is with SIPs or conventional stick construction, it is recommended that a regular preventive program of insect treatment be initiated and maintained when building in a known insect risk area. Most pest control companies offer maintenance plans, renewable periodically or annually, and will automatically treat your grounds and structure at pre-determined intervals. With such a program and proper maintenance of the property, you should be able to comfortably minimize the risk of insect infestation.
There are no empty cavities in a SIP in which mold and mildew can propagate. However, because of the airtight building envelope SIPs create, high moisture levels can result in mold and mildew growth if the moisture is not properly controlled through mechanical dehumidification and ventilation.
If a SIP sustains physical damage, a structural engineer should be consulted to determine the extent of the damage and whether the structural integrity of the structure has been compromised. If the damage is from moisture, the moisture source should be identified and mitigation performed. Should the SIP or SIPs require replacement, contact the builder or installer, and the manufacturer.
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The construction of a SIP building begins with the design and construction drawings and documents. These are provided to the SIP manufacturer who uses the construction documents to develop detailed SIP shop drawings. Once the shop drawings are approved by the homeowner, builder, or professional contractor, the SIPs are fabricated and shipped to the jobsite.
Murus does not offer design services, but we would be happy to work with you and your designer to maximize the efficiency of your SIP home.
Each project is unique and so are the load and span requirements for that project. Murus can provide the necessary information for your specific application - please call us at (800) 626-8787.
We’ll need a good set of plans that include dimensions and elevations so we can estimate material quantities and service costs for you.
Mark your plans and documentation to the attention of the Murus representative you spoke with, and send them to:
The Murus Company, Inc.
PO Box 220 (for US Mail)
3234 Route 549 (for FedEx, UPS, etc.)
Mansfield, PA 16933
For Pre-cut Panel orders, plan on a minimum of six to eight weeks from the time Murus receives your signed order, deposit, and drawings for standard OSB panels. This time frame can vary, so check with your Murus representative for current lead times.
Murus SIPs are stacked in bundles and wrapped in heavy gauge black plastic prior to shipping. The plastic provides protection during typical installation time frames. SIPs should be stored on level risers that elevate the panels high enough off the ground to create an air flow beneath the bundle. This will help inhibit ground moisture from condensing on the underside of the bundle. For extended storage of SIPs, Murus recommends placing the wrapped panel bundles in a fully enclosed structure that provides protection from exposure to wind, rain, moisture, and UV light. In the absence of structure availability, it is recommended that the SIPs be covered with proper protective tarping until ready for use. Do not stack bundles more than two high. For more information, refer to the Murus Panel Installation Manual.
Murus SIPs should be completely covered as quickly as possible upon installation with code-approved weatherproof roofing, siding, and trim materials to prevent exposure of the OSB to the elements and to UV rays.