Several influences in today’s design strategies focus on improving the energy efficiency of buildings, in both new and retrofit situations. Key considerations include federal mandates to achieve net-zero energy by 2020, as well as private sector energy cost savings benefits. Energy efficiency represents the greatest opportunity for points and credits in non-governmental organization programs such as the U.S. Green Building Council LEED building certifications. In addition, green building codes such as the International Green Construction Code and ASHRAE Standard 189 (an accepted alternative to the IGCC) also focus on improved energy efficiency. Other similarly focused programs include the Energy Star Challenge, Energy Efficiency and Renewable Energy Building Technologies Program, Zero Energy Commercial Buildings Consortium, the National Institute of Building Sciences Building Enclosure Technology and Environment Council, and the High-Performance Building Council. Additional influences come by way of tax incentive programs for commercial and industrial buildings.
ASHRAE Standard 90.1 is the world’s most adopted building energy code standard that addresses energy efficiency. The standard is the basis for the International Energy Conservation Code and serves as a compliance option for IECC. In late 2010, ASHRAE Standard 90.1-2010 adopted an aggressive goal of 30 percent energy-cost savings over the 2004 version of the standard.
ASHRAE 90.1 and Metal Buildings
ASHRAE 90.1 includes specific tables that identify minimum R-, U-, and F-values for metal walls and roofs. Ongoing discussions continue at the 90.1 Envelope Subcommittee regarding recommendations of single-skin metal assemblies and effective R-values versus reported R-values.
A recent issue that has been addressed is that Standard 90.1 does not represent insulated metal panels and single-skin metal assemblies in the same way. Many thought leaders argue that IMPs should be considered in the tables by reported U-Value requirements.
Path to Net-Zero Energy
At Greenbuild 2010 in November, the presentation “Insights in Energy Costs Savings, Envelope Performance and NZE” was presented as a panel discussion that included Peter Baker, Building Science Corp.; Roger Hedrick, Architecture Energy Corp.; and Michael Deru, National Renewable Energy Laboratory. The basis of the presentation was an energy modeling study commissioned by Deland, Fla.-based Kingspan Insulated Panels and conducted by the Architectural Energy Corp., Boulder, Colo., that compared metal buildings that feature pre-engineered IMPs to traditional site-built exterior cladding systems, including: tilt-up, exterior insulation and finish system, split-face block and single-skin metal with blanket insulation. The roof baseline building is standard membrane with deck.
A simulation analysis was performed to evaluate the energy efficiency impact of constructing typical buildings with high-performance insulated metal panel wall and roof systems, and the additional steps necessary to achieve net-zero energy buildings. Three buildings-school, office and warehouse-were simulated in four locations, each with different climate zones. Following the evaluation, the building envelope was improved with continuous insulation wall and roof system IMPs.
Typical energy conservation measures, which varied by building type, were then applied, and finally, photovoltaic arrays were sized to achieve energy savings of 30, 50, 70 and 100 percent over the baseline buildings. The results showed that the increased insulation and reduced air leakage of the high-performance IMP wall and roof construction achieved significant energy savings. This was particularly true for the school building, with a configuration that resulted in a large surface to volume ratio. Energy savings for the IMP construction alone were as high as 22 percent. For the office and warehouse, which had much lower surface to volume ratios and higher internal loads, the energy savings were lower, but still ranged up to seven and 19 percent, respectively.
Achieving net-zero energy buildings requires two distinct but complementary aspects of a building’s design. First, the building must be made as energy efficient as possible. Second, the building must include a means of producing energy from renewable resources.
Improving the energy efficiency of buildings involves a wide variety of approaches and envelope design options, including:
- Building orientation and configuration for solar heat gain and daylight availability
- Increased wall and roof insulation
- Air sealing to reduce infiltration
- Cool white roof
The 42-page white paper from AEC goes into great detail and is available at www.kingspanpanels.us. This study was converted into a mobile app, designed for iPad, iPhone, iPod Touch and Android devices, and is available for free download at the App Store and Android Market. Visitors to the microsite (www.pathtonetzero.com) can find exclusive information on net-zero energy buildings and request an energy analysis of their buildings. The goal of this study is to help design teams understand the critical aspects of designing a building envelope for maximum optimization before adding energy conservation measures and renewables. The app was designed to equip architects and the design community with the tools to explore the possibilities of various wall and roof R-values along with energy cost savings, greenhouse gas reduction, return on investment, and LEED points and credits, all of which need to be considered in a project energy modeling exercise.
Paul R. Bertram Jr., FCSI, CDT, LEED AP is a director, environment and sustainability, for Deland,
Fla.-based Kingspan Insulated Panels North America. He is also a Fellow of the Construction Specifications Institute and President Elect of the Institute, with a focus on climate change, building product environmental impacts and Net-Zero Energy strategies.
