Policymakers and the public are increasingly interested in reducing energy use. Whether due to a desire to reduce costs, greenhouse gas emissions, or imported energy, achieving these goals will depend on actual and measurable results. Numerous approaches exist to reduce energy use. Model energy codes provide baseline requirements (where adopted). Green building programs provide additional guidance. Benchmarking and companion operations and maintenance practices along with ongoing commissioning also support achievement of performance goals. (See also Meet Performance Objectives; Optimize Energy Use; Building Commissioning; Optimize Operational and Maintenance Practices.)
Model Energy Codes and Performance
Current model energy codes and standards only provide criteria prescribing how buildings are to be designed and constructed. The provisions in virtually all energy codes and standards are based on a number of prescribed criteria that must be satisfied by specific products, materials and components of a building. Unfortunately, many of those criteria do not account for the application of new technologies such as innovative window materials or creative design approaches such as passive solar, building form and shape, and orientation. Current codes also do not cover all the energy consuming functions in a building, even though these functions contribute to the overall energy use and influence the energy use of equipment covered under the code. Plug and process loads, and elevators and escalators generally are not included. In California, for instance, plug loads account for about 40% of overall energy use in buildings—closer to 65% in hospitals and restaurants.1
The closest these documents come to actual performance of a building is a simulation of how a building as designed is expected to perform compared to the same identical building but assumed to just meet the provisions in the code. In effect, this creates a custom energy budget for each and every building based on a prescriptive foundation.
An analogy can be made between the outcome-based requirements for a building to the purchase and use of an automobile. When purchasing a vehicle you are given information about the vehicle's performance in its specifications and the mileage that is anticipated for its operation. However, your personal performance and mileage may be quite different. Only by checking the actual mileage can you know whether what was stated is being achieved. Similarly, under traditional energy codes and standards, when the building is completed and is occupied there is no way to know whether the decisions for a specific design or material or orientation resulted in actual energy savings.
Options for Implementing Outcome Requirements
Outcome-based approaches provide a real target, allow design options and flexibility and then provide real answers as to whether what was planned has been achieved in a way that has never been done before. They allow for designs to incorporate operations and management or tenant behavior.
Outcome-based pathways can take numerous forms including:
Outcome-based codes establish a target energy use level and provide for measurement and reporting of energy use to assure that the completed building performs at the established level. Such a code can have significant flexibility to reflect variations across building types and can even cover existing or historic buildings. Most importantly, it can address all energy used in buildings and provide a metric to determine the actual quality of the building construction. Such a pathway is included in the 2015 International Green Construction Code (IgCC) and is being considered for inclusion in the 2018 International Energy Conservation Code. The city of Seattle has incorporated a "Target Performance Path" into their energy code.2
Owner-Established Outcome Requirements may be written into contracts for design teams. Such requirements may be applied above existing code requirements or by entities without requirements to meet codes (e.g., federal government or areas without energy codes). The General Services Administration's Federal Center South Building 1202 employed such a requirement. The design-build team has 0.5% of the original contract value at risk pending verification of the building's energy performance after one year of occupancy. This risk is shared between design-builder/contractor, architect, major subcontractors, and design consultants who have primary responsibility for the building's energy performance. At the end of the first year verification period, any remaining construction contingency will be shared between the construction and the design team. Such an approach requires the full engagement of the entire design and construction team, establishment of owner's performance requirements, and ongoing performance evaluation.
Design-Build-Operate-Maintain or Public-Private Partnerships depend on the establishment and fulfillment of performance requirements in order for the building team to meet the terms of agreement with the occupying entity. While these types of arrangements are currently limited in the U.S. buildings sector, their potential use has garnered significant attention.3 The George Deukmijan Courthouse (Long Beach Courthouse) project utilized this approach.
While current calls for an outcome-based pathway focus on utilization for highly-engineered buildings and sophisticated building owners and code departments, or for upgrades in existing and historic buildings, tools for utilizing an outcome-based process on small, non-complex buildings may evolve. For small, non-complex buildings with tight budgets, prescriptive requirements may still be desirable, and could be developed utilizing the outcome-based targets. It is possible to envision multiple parties establishing prescriptive pathways to reach specified energy targets. For example, an HVAC manufacturer or association might develop prescriptive pathways that feature very high-efficiency mechanical equipment, while other interests might develop pathways for daylighting / lighting controls or high-efficiency envelope performance.
Energy targets for current outcome-based approaches may be based on the Energy Information Administration's Commercial Building Energy Consumption Survey.4 CBECS provides data based on a survey of some 5,000 buildings of different types from across the country. As of February 2011, however, only data from the 2003 survey was available, and some building types do not have statistically significant data for certain climate zones. Improvements to CBECS or other sector-wide datasets will be necessary to have a meaningful baseline and to monitor progress toward net-zero energy goals. Reported energy use based on implementation of outcome-based codes or the expanding interest in labeling and disclosure requirements can start the development of a meaningful database.5 If outcome-based requirements are established by a building owner, they may look to other buildings within their portfolio to set performance requirements.
- "Alternative Formats to Achieve More Efficient Energy Codes for Commercial Buildings" by Conover, D.; M. Rosenberg, M. Halverson, Z. Taylor and E. Makela.
- Compliance Verification Paths for Residential and Commercial Energy Codes PNNL, September 2011.
- Consultative Council on Construction Codes and Standards
- "Developing Effective Codes and Standards for Net-Zero Energy Buildings" by Colker, R.M., D. Hewitt and J. Henderson. Building Design + Construction White Paper on Zero and Near-Zero Energy Buildings + Homes, March 2011.
- "Focus on the Outcome, Not Just the Design: Codes, Standards + Rating Systems" by Frankel, M. ECOHOME Magazine, Winter 2013.
- "Getting to Outcome-Based Building Performance Event Report" by Frankel, M., J. Edelson, and R. Colker. May 2015.
- Implementing an Outcome-Based Compliance Path in Energy Codes: Guidance for Cities, National Institute of Building Sciences and New Building Institute, October 2017.
- "Outcome-Based Codes: Answering the Preliminary Questions" by Colker, R.M. Strategic Planning for Energy and the Environment, Spring 2012.
- Outcome-Based Energy Codes, New Buildings Institute
- "Procurement Path for Energy-Efficient Buildings" ASHRAE Journal, April 2015.
- Public-Private Partnerships for Public Facilities Legislative Guide, American Institute of Architects
- "Rethinking Compliance Verification" by Colker, R.M.; D. Conover and T. Ryan. DesignIntelligence, September/October 2012.
- IECC Proposed Outcome-Based sponsored by the National Institute of Building Sciences on Oct. 6, 2016.
- Energy-Performance-Based Acquisition for Commercial Buildings, U.S. Department of Energy
1 [Rethinking Percent Savings, by Architectural Energy Corporation]
2 [2012 Seattle Commercial Energy Code Involves Building Managers and Occupants, Building Connections]
3 [RICS Research Report Private Finance Initiative and Public Private Partnership]