Achieving real-world building energy performance
Project goal setting is one of the most important aspects to creating a high-performance building. However, not all goals are created equal. Starting off with good intentions, many project teams hold early design charrettes that discuss and outline project performance aspirations. Too often these aspirations fall into the periphery, pushed aside by other forces such as budget, lack of communication, or poor planning. By establishing clearly articulated and measurable targets, project performance goals have a better chance of remaining front-and-center throughout the design process (see Table 1).
The best goal has clear criteria for success. This allows the design team to work creatively toward an objective that can be solved. Energy use intensity (EUI) is a measureable target expressing building energy consumption over the course of the year, normalized over the gross floor area.
A recent trend that takes these goals one step further is to incorporate energy performance targets within project contract documents and proposal processes. Similar to a set budget, program, and timeline, performance targets articulate a desirable outcome resulting in a better building. Design teams that are comfortable delivering successful projects that achieve a green building rating, such as U.S. Green Building Council LEED certification or Energy Star, should be capable of making this transition.
Owners that have successfully used performance-based design contracts include major universities, the General Services Administration, and the National Renewable Energy Lab (NREL). NREL has published several documents further outlining its procedures.
Upfront planning is necessary to set meaningful and realistic energy goals. Using a combination of existing building energy use surveys and preliminary modeled performance is a good starting point. This allows initial assumptions on building operations to be made upfront. There are risks associated with the predictability of real-world energy consumption. Energy models are only as good as the inputs going into them. Communication as early as the proposal process between building owners and the design team is necessary. This may entail benchmarking existing facility plug loads, or discussing the occupant’s ability to alter energy performance. It is important that a contingency procedure is developed to not penalize design teams if there are major changes in program or operation of the building after the target EUI is established. A simple way to accomplish this is to prorate energy results based on changes seen during the measurement and verification process.
Owners need to be steadfast in sticking to their original goals and allow the design team to work through design decisions informed by whole building energy modeling coupled with lifecycle costing. If there are multiple goals, creating a prioritized list of desired results will allow teams the freedom to innovate while maintaining critical objectives.
Incentivized outcomes can be a good motivator for the design team. One method is to retain a certain percent of the project budget released on the contingency that objectives are met after 1 to 2 years of operation. Not only does this encourage thoughtful design, but it also will prompt increased scrutiny of building operations during the measurement and verification period if assessed by the design team.
Historically, projects using energy performance contracts have used an integrated delivery process or other form of design-build. This helps establish a clear procedure for who is ultimately responsible for on-budget energy performance. Conventional design-bid-build could still be considered; however, care must be taken to create a chain of responsibility from beginning to end. In addition, accurate incremental costing will play an important role in the decision-making process.
Keep in mind this design method is not just for energy. It could be used for many measurable outcomes such as comfort, indoor air quality, acoustics, usable daylight, or water consumption.
With building rating schemes pushing for verification, along with outcome-based energy codes and city energy disclosure ordinances continuing to develop, there is no doubt that energy performance-based contracts will become more prevalent. Empowering all members of the process, success will come down to the owner’s resolve and designer’s commitment to solving the project objectives.
Connor Jansen is senior project manager at Seventhwave, formerly the Energy Center of Wisconsin. His background includes work in high-performance buildings through consultation and analysis on energy, indoor environmental quality, and daylighting metrics.