Originally posted in Construction Executive Magazine, June 2011 edition:
By James Hodgson
It’s only a matter of time before all clients start expressing interest in net-zero energy buildings. With energy prices climbing, building owners are increasingly looking to cut their consumption—with the prized goal of developing new facilities that produce as much power onsite as they use. Government and institutional facility managers are especially focused on achieving high energy efficiency given their constricted operating budgets and the green mandates many of them face.
Although solar panels and wind turbines capture the public’s attention, the Zero Energy Commercial Buildings Consortium (CBC) states, “viable low-energy or net-zero energy buildings must first aggressively maximize energy efficiency before integrating renewable energy.” For new facilities, this means creating a tight building envelope.
The historic approach to construction has been to erect the building, insulate it and seal the gaps. This method results in a multitude of areas for potential air leakage and thermal bridging, such as between exterior wall studs and roof joists and where wall and roof sections join. Given the variability in building designs and site conditions, getting the envelope tight can be difficult.
An Alternative Approach
Rather than installing the structural elements and insulation separately, a faster and more effective approach is to use wall and roof components that integrate these systems. Commonly available examples include structural insulated panels (SIPs) and insulated concrete forms (ICFs). Many contractors use ICFs below grade and SIPs above ground to create high-performance building envelopes.
U.S. Department of Energy research shows SIPs are 15 times more airtight than stick framing and have higher whole-wall R-values. The agency’s tests found that a wall built with 3½-inch thick foam core SIPs was R-14.1, while a two-by-four stud wall at 16 inches on-center with fiberglass insulation was R-9.6—a 47 percent higher R-value for SIPs. Additionally, because insulation is continuous throughout each SIP, there is less thermal bridging than with many other building methods.
The high-performance insulation of SIP walls and roofs helps reduce heating and cooling energy consumption up to 60 percent. A tight SIP envelope saves utility costs throughout the building’s life; plus, because the equipment cycles on and off less frequently, the SIPs reduce HVAC maintenance and replacement costs.
Building professionals can use SIPs in all types of low-rise buildings, including offices, medical facilities, single- and multi-family homes, restaurants, hotels and government buildings. It is relatively straightforward to adapt virtually any wood-framed structure, concrete block or similar design to SIP construction.One particular growth area for SIPs is public and private schools. Educational facility project teams choose SIPs for their energy savings, as well as their rapid installation. Because school administrators often require new or replacement schools to be completed under strict schedules determined by the school year, rapid dry-in is a must. SIPs arrive at the jobsite in pre-cut, labeled pieces that are ready to install following specified layouts. Manufacturers can provide the panels with window and door openings and electrical chases to further reduce field labor.According to the project manager for a new middle school in suburban Seattle, utilizing SIPs supported the strategies for energy savings, as well as allowed for a smooth and rapid assembly process—shaving weeks off a tight construction schedule.
In some cases, the initial construction costs of SIP buildings are similar to other methods, especially when factoring in the fast cycle time and potentially lower subcontractor labor. However, SIP costs might be higher for complex projects. The deciding factor typically comes down to performance. For projects where high energy efficiency is paramount, owners may be willing to pay a premium upfront in exchange for greater long-term savings.
Constructing code-compliant SIP buildings is no more challenging than traditional construction methods. The primary codes—including the International Building Code and International Residential Code—recognize SIPs for many building types. In instances where local code officials request additional details, the SIP manufacturer can provide code evaluations and technical reports for its specific panels.
Net-Zero Energy Buildings Today
As the CBC notes, “the move to net-zero energy buildings will require building envelope systems to provide superior performance over a wider range of conditions than in typical commercial buildings today.” Although building codes and owner demands are continually ratcheting up energy efficiency requirements, readily available technologies and methods exist now for developing tight envelopes.
Project teams can use advanced structural components, such as SIPs, in conjunction with high-efficiency windows and doors, advanced heating and cooling systems, automated lighting controls and onsite power generation to reduce energy use dramatically. With such methods, it is possible to meet the most stringent goals for energy efficiency that will kick in during the next several decades.
James Hodgson is general manager for Premier Building Systems. For more information, call (800) 275-7086