SIPs Time & Motion Study

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Residential building contractors are under increasing pressure to provide higher performance homes at lower cost and in shorter construction time. BASF Corporation is one of the largest multi-national chemical manufacturers in the world, with a portfolio ranging from chemicals, plastics, performance and agricultural products, to crude oil and natural gas. They supply the adhesive used to join the foam to the OSB, the resins in the OSB, and the foam core used in structural insulated panels (SIPs).

As the leading cost consultant and supplier of construction cost information in North America, Reed Construction Data/RSMeans provides third party validation of labor and productivity savings available to manufacturers. BASF needed an analysis of the cost benefits and efficiencies associated with installing SIPs, and commissioned the RSMeans Business Solutions team to design and perform a Time & Motion Study that would quantify the insulation productivity differences between using SIPs and conventional framing.

The research objective was to evaluate the installation time and cost associated with SIPs, as compared with conventional framing comprised of 2 x 6 framing, and oriented strand board (OSB) sheathing, to which thermal insulation and an air barrier are added. SIPs are load-bearing components that form structural exterior wall assemblies, complete with sheathing, insulation, and air barrier. It was expected that because SIPs eliminate a few steps in the building process, it would speed up construction job site time.

Specifically, the Time & Motion Study would quantify the following productivity differences of conventional framing vs. SIPs panels:
a. Labor and cost savings
b. Greater efficiencies and ease of use over conventional framing methods
c. Productivity differences for residential framing and electrical rough-in

Key findings that emerged from the Time & Motion Studies:
• The use of prefabricated Structural Insulated Panels resulted in significant time and labor cost savings. Erection of the SIPs walls, roof, and dormers took 45% of the labor hours expected for conventional construction.
• Rough-wiring the electrical appurtenances in the SIPs walls took 89% of the labor hours expected for rough wiring in a conventional house. (Hourly rates for the electricians were the same for both types of construction, so the labor cost savings matched the labor hour savings.)

Other advantages for SIPs include:
• SIPs eliminate the need to install exterior sheathing, thermal insulation, and housewrap separately. The SIP sandwich panels come preassembled, which reduces installation time.
• Precut openings: with door and window openings already cut, there is less labor required on the job site to install SIPs.The following observations made in the field may be helpful to contractors using SIPs:
• Optimum crew size: a foreman who can double as the crane operator, two carpenters, and one helper. For rough-in wiring, three electricians will save coordinating time.
• SIPs installation requires the use of a truck-mounted crane and a qualified operator. Such equipment and training is not typical for a residential framing crew.
• Panels need to be carefully checked to make sure they fit before they are shipped to the job site.
• Plans should be checked to be sure the panels and openings are correctly dimensioned.
• Field-cutting panels should be avoided whenever possible, as errors could result, causing long delays waiting for replacements to be shipped.

Conclusions and Recommendations

The RSMeans Business Solutions team concluded that not only does using prefabricated SIPs save significant time on site, it reduces labor costs. In addition, rough-in wiring with prefabricated wire chases further increases these savings.

Although life cycle costs were not part of this study, it should be noted that SIPs installed to meet Energy Star requirements offer significant savings in energy use. A typical 2’ x 6’ wall with fiberglass batt insulation has an R value of 19 while the comparable SIPs wall is rated at R 22.3. In addition to the higher R values, the sealed joints between the SIPs reduce air leakage (drafts) and energy loss.

Energy efficiency is a very attractive selling point with many potential buyers, despite the higher material costs of SIPs, because they minimize heat loss/gain in a new home, increase comfort, and save money in the long run.

BASF may wish to evaluate labor and materials differences between equivalent wall configurations (i.e. a 2 x 4 wall compared to a nominal 4 inch SIP wall.) Similarly, an R-19 SIPs wall could be compared to a "high performance" 2 x 6 conventionally framed wall.

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SIPs Design Manual

Detailed planning and designing information on Premier Structural Insulated Panels (SIPs)