This technical paper from the US Department of Energy’s Building Technologies Program reviews a four-year study of six buildings, to identify issues related to the design, construction, operation, and evaluation of the current generation of low-energy commercial buildings.

The US DOE estimates that commercial buildings account for about 18% of the total primary energy consumption in the U.S., and so has developed a goal to ‘create the technology and knowledgebase for marketable zero-energy commercial buildings (ZEBs) by 2025’.

This study is in support of that goal, and uses detailed case studies of six buildings to help inform a set of best practices - beneficial design elements, technologies, and techniques that should be encouraged in future buildings, as well as pitfalls to be avoided.

Below is a summary list of lessons learned that applied to all six case study buildings:

• Owners provide the main motivation for low-energy buildings. The owner was the driving force in each case. Each owner set the goals and made decisions to keep the project on track. The architects and engineers strived to meet the goals of the building owners, which resulted in the need for the whole-building design process.
  

  
  

• Setting measurable energy saving goals at the outset of the project is crucial to realizing low-energy buildings. In the case studies, all the owners and design teams set aggressive energy saving goals at the outset. The goals ranged from 40% better than code to net-zero energy performance. In general, the teams that set the strongest energy performance goals and used energy simulation to understand the energy impacts of design decisions had the best energy performance.
  

  
  

• Many decisions are not motivated by cost. Building owners make decisions based on values. Quite often owners will pay for features they really want in a building—this is especially true of architectural features. Conversely, if an owner does not want a feature, cost is often used as the reason to eliminate it.
  

  
  

• Today’s technologies can substantially change how buildings perform. Properly applied off-the-shelf or state-of-the-shelf technologies are available to achieve low-energy buildings. However, these strategies must be applied together and properly integrated in the design, installation, and operation to realize energy savings. There is no single efficiency measure or checklist of measures to achieve low-energy buildings.
  

  
  

• A whole-building design approach is a good way to lower energy use and cost. An integrated whole-building approach begins with a design team that is committed to the energy goals. The building must be engineered as a system if the technologies are to be integrated in design and operation. This included using computer simulations to help guide the design process—these simulations can perform trade-off analysis to examine energy impacts of architecture choices and HVAC&L (heating, ventilation, air-conditioning, and lighting) designs.
  

  
  

• Low-energy buildings do not always operate as they were designed. The design community rarely goes back to see how their buildings perform after they have been constructed. Measurements in all six buildings showed that they used more energy and produced less energy than predicted in the design/simulation stage.
  

  
  

• Information leads to better management and improved performance. Setting and following design goals or traditional commissioning does not guarantee that the goals will be satisfied in actual operations. The whole-building energy performance must be tracked and verified. Monitoring provides valuable feedback that can help maintain the efficient performance of systems to ensure design goals are met.
  

  
  

• This set of current generation low-energy buildings shows progress toward achieving a ZEB goal in actual buildings. Each of these buildings saved energy, with energy use 25% to 70% lower than code. Although each building is a good energy performer, additional energy efficiency and on-site generation is required for these buildings to reach DOE’s ZEB goal. At current levels of performance, the one-story buildings—Zion, BigHorn, and TTF—could accomplish the ZEB goal with PV systems that would fit within the building footprint. ZEBs are not feasible for the two-story buildings within their footprints unless their loads are reduced.
  

  
  

• We can replicate the lessons learned from these case studies in future low-energy buildings. Even though every commercial building is unique, the lessons learned from these case studies can be applied to a wide variety of commercial buildings. The buildings and the lessons learned from them help to define a set of best practices. Best practices are proven real-world technologies and processes that lead to high-performance buildings. Understanding success and opportunities in the current generation of low-energy buildings can improve the energy efficiency of all commercial buildings—the best practices should be applied to future buildings.
  

The entire technical paper can be read here (PDF).