Most construction professionals are familiar with the “Project Management Triangle,” a concept that ties cost, schedule, scope and quality together. Impact any of these project elements, and you impact the others. Academics frequently presents the triangle as an inflexible set of constraints. Nonsense.
Under any given construction practices, the Project Management Triangle may apply, but it is not absolute. Contractors through history have regularly developed or implemented better, faster and more cost effective building methods.
Today, the commercial construction industry faces numerous competitiveness, and often conflicting, priorities – from tighter budgets to building greener, while still needing to retain high quality. This environment requires a careful look at more advanced building techniques.
One such method is structural insulated panels (SIPs). The panels provide many benefits compared to other light commercial construction such as stick-built framing, concrete masonry units (CMUs), and tilt-up concrete. These include faster close-in times, high strength, and several important green building attributes.
Building with SIPs
SIPs are pre-manufactured wall, roof or floor components delivered to the jobsite ready to install in sections up to 8 feet by 24 feet long. They are typically made with oriented strand board (OSB) laminated and pressure cured to a rigid insulating foam core.
Manufacturers have produced SIPs for several decades, and building professionals now use them in many building types. Common applications include single- and multi-family homes, schools, churches, offices, retail, and most other light commercial buildings.
The design and construction process with SIPs is straightforward. The architect provides the construction documents to a SIP manufacturer or dealer, who converts them into shop drawings that show each panel's specific dimensions. After review by all applicable parties, the manufacturer or dealer finalizes the shop drawings, makes the panels, and delivers them to the jobsite pre-numbered to coordinate with installation plans.
Fast Close-in Times
A key advantage SIPs provide in today's tight economy is their ability to dramatically reduce dry-in time. The large, single-piece panels enable contractors to install entire wall, roof and floor sections at one time. They eliminate the need for separate framing, insulating and sheathing work on site, and enable subs to start and finish work faster since walls, roofs and floors are plumb and square.
In addition, manufacturers pre-cut window and door openings, including curves, arches and complex shapes. Depending on an opening's dimensions, sub-contractors do not need to spend time installing separate headers. The panels also come with pre-cut electrical chases, eliminating the need to drill through studies for wiring.
In a new elementary school built with SIPs, the Clark County School District (Las Vegas, Nevada) reduced close-in time by approximately 80 percent – from a typical 118 – 220 days to only 45 days. “The general contractor was shocked at how fast the panels installed,” said Gary Radzat, President of Shell Building Systems, Sebastopol, California), the SIPs design and installation consultant for the Jacob E. Manch Elementary School. “He said he'd never seen that size of schedule reduction.” Using SIPs saved the district approximately one million dollars in direct construction costs.
As construction leaders know, faster building cycle times significantly reduce interest payments on construction loans – an important factor in a healthy bottom line.
High Strength and Consistency
SIPs are very strong and in most applications are structurally self-sufficient. Designers can use them in wall, roof and floor systems in place of other structural elements.
While frequently used in one-or two-story buildings, they have been successfully utilized for taller structures. Last year, Western Wyoming Community College (Rock Springs, Wyoming), opened a 28,000-square-foot housing complex with 48 bedrooms spread through four stories – the tallest self-supporting SIPs structure built to date.
In walls, SIPs can bear high loads and offer great strength in racking diaphragm shear capacities. These capabilities enable the panels to be used in typical exterior walls, as well as shear walls to resist earths and high winds. Extensive testing on SIPs has proven them for use in high-risk earthquake areas, including seismic zones D, E and F.
In roofs, SIPs can be used without an engineered truss system and can span long distances – up to 20 feet based on design parameters. As a result, they can help create open interior spaces by reducing the need for intermediate structural support.
Designers can also incorporate SIPs into floors, typically in applications such as over crawl spaces where an insulated floor system is required.
SIPs play an important role in ensuring quality finishes. Because they are made in a controlled setting and come in large sections, they allow for straighter walls than is possible with wood stick-built framing. Their smooth and even surface can also reduce finishing labor by helping eliminate the need to shim cabinets, windows and doors.
Green Building Benefits
To help meet green building goals, designers and contractors are increasingly specifying SIPs because of their numerous environmental attributes. Notably, SIPs reduce energy costs, as well as construction waste, up to 60 percent, and play a role in improving indoor air quality and supporting recycling.
SIPs provide exceptional energy efficiency compared to other construction methods because they combine insulation and structural elements in one unit.
By contrast, with stick framing or concrete construction, insulation is added after the structure is built. It is difficult to apply fiberglass batts or blown-in insulation without leaving gaps, especially in corners and other hard to reach places. Also, because SIPs come in large sections, there are fewer gaps to be filled, resulting in a tighter building envelope.
When evaluating the R-values of whole wall assemblies, the US Department of Energy's (DOE) Oak Ridge National Laboratory found that a 3.5-inch-wide core SIP provided a whole-wall R value of 14.1 compared to a 9.6 whole-wall R value of a 2×4 framed wall with studs at 16 inches on center and fiberglass batts. A 4.5-inch SIP wall also outperformed a 2×6 wall with R-19 fiberglass insulation.
The improved insulation reduces engoing energy use and costs, plus helps reduce HVAC system requirements. On the Las Vegas Manch School, project consultants estimate that SIPs reduced the HVAC equipment capacity needed by approximately half.
In addition, energy efficient building materials such as SIPs may qualify commercial building owners for up to a $ 1.80 per square foot tax deduction.
The lower operating costs of a SIPs building can be a key market differentiator, helping developers sell or lease commercial space easier.
Construction waste reduction and recycling
Stick-built construction generates large scrap volumes from cutting stock size studs and joists to length. Since SIPs are manufactured in a controlled setting, more careful material management is possible than on a jobsite. In addition to reducing the environmental impacts created by a large waste stream, SIPs can reduce disposal fees.
Many SIPs are 100 percent recyclable, as well as have foam cores made from a specified level of recycled content. The OSB skins come from fast-growing, renewable trees, and are manufactured using a high percentage of each log for efficient resource use.
Indoor air quality
Because SIPs provide a tight building envelope, they help reduce infiltration of common pollutants such as radon, molds, pollen, volatile organic compounds (VOCs), lead dust and asbestos. Manufacturers typically produce SIPs without the use of CFCs, HCFCs or formaldehyde, and zero-VOC mastics are available. In conjunction with other low-emitting building materials, SIPs can help support healthy indoor air, which the US Environmental Protection Agency (EPA) reports is linked to employee and student performance and attendance.
Given their multiple environmental advantages, building professionals can use SIPs to earn up to 23 points under the US Green Building Council's (USGBC) Leadership in Energy and Environmental Design (LEED®) for New Construction Rating System. Depending on the project and overall design, key point categories to consider are “Energy and Atmosphere,” “Materials and Resources,” and “Indoor Environmental Quality.”
Planning, designing and construction commercial buildings is more challenging than ever. To survive, and even thrive, in the down market requires new ways of thinking. SIPs are a tested and trusted construction technique that offers a way to greatly improve light commercial construction.