Commercial Building Design and Performance

The U.S. Department of Energy's Buildings Technologies (BT) Program set a goal to reach net zero energy buildings by 2025. The real question is, can we reach zero energy buildings and what kinds of technology improvements will be required? The answer to the first part is "yes," but the answer must be qualified. The definition of what constitutes a zero energy building is important. In addition, it is important to note that some buildings can easily get there while others have more energy intensive loads. Below is information on prior buildings research work related to zero energy buildings.

• Zero Energy Buildings Defined
• National Energy Use Assessment
• Performance Metrics
• Benchmarks
• Case Studies

Definition

A net zero-energy building (ZEB) is a residential or commercial building with greatly reduced energy needs through efficiency gains such that the balance of energy needs can be supplied with renewable technologies. Despite the excitement over the phrase 'zero energy,' we lack a common definition, or even a common understanding, of what it means. In this paper, we use a sample of current generation low-energy buildings to explore the concept of zero energy: what it means, why a clear and measurable definition is needed, and how we have progressed toward the ZEB goal. For more information, see "Zero Energy Buildings: A Critical Look at the Definition." (PDF 477 KB) Download Adobe Reader.

Assessment Report

NREL conducted an assessment of the entire commercial buildings sector to evaluate the technical potential for meeting DOE's zero energy buildings goal with technology available in 2005 and projected forward to possible technology improvements for 2025. The analysis looked at the technical feasibility of ZEBs, limitations in market penetration and utility grid structures, notwithstanding. A research report was published internally by NREL, but a conference paper summarizing that report is available online at: (PDF 685 KB) Download Adobe Reader.

Performance Metrics

The Performance Metrics Research Project is a research activity to standardize the measurement and characterization of building energy performance. Obtaining reliable metrics for determining a building's performance was identified by the commercial building industry as one of the core challenges to achieving widespread adoption of high performance buildings. The first objective of this project is to determine which performance metrics are of greatest value for energy consumption and on-site energy production. The second objective is to develop standard methods of measuring and reporting the performance metrics. For more information, visit DOE's Performance Metrics Research.

Benchmarks

Many national laboratories and universities conduct buildings research. However, differences in models and simulation tools used by these various research groups make it difficult to compare results among studies. NREL has developed a set of 22 benchmark buildings and weighting factors for nine locations across the country, for a total of 198 buildings. The benchmark buildings represent new commercial buildings and meet minimum ASHRAE 90.1-2004 standards. The benchmark building definitions are complete descriptions suitable for whole-building energy simulations and are implemented in EnergyPlus input files. The benchmark building definitions will be available as technical documents near the end of 2006. These buildings will form the basis of NREL's research on specific building technologies, energy code development, appliance standards, and measurement of progress toward the DOE energy goals. Having a common starting point allows us to better share and to compare research results and move forward in making more energy-efficient buildings. In addition, the benchmark buildings can be used with minor modifications to evaluate other energy efficiency programs and individual buildings.

Case Studies

NREL studied six commercial buildings in detail over a four-year period to understand the issues related to the design, construction, operation, and evaluation of the current generation of low-energy commercial buildings. These buildings and the lessons learned from them helped 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. The lessons learned from these six buildings are also used to guide future research on commercial buildings to meet DOE's goal for facilitating marketable ZEBs by 2025. For more information, read "Lessons Learned from Case Studies of Six High-Performance Buildings." (PDF 3.8 MB) Download Adobe Reader. Detailed research reports are available on the High Performance Buildings Database for the case study project buildings.