Green Building Challenge (GBC) was intended to advance the state-of-the-art of building performance assessment, through the development, testing, and discussion of an assessment framework, criteria and tool. The contributions of GBC to building performance assessment are considered through comparing similarities and differences with a selection of available assessment tools. Unlike national or proprietary assessment systems, GBC was not designed for application to specific commercial markets. Instead, it emphasized research and involved researchers and practitioners from many countries. Consequently, GBC has been in a unique position to test and adopt new ideas and implement step changes. GBC's roles over the past five years have been to provide a reference framework, method and tools that can be used to develop new systems or improve existing systems; provide a forum for discussion among researchers and practitioners worldwide; and raise awareness and credibility of assessment systems. GBC's role has evolved as the context in which it operates has changed. Based on the analysis on GBC's specific characteristics and strengths, its potential future roles are found to reside in a unique position. Its role as a reference system has become less important to many participants as they implement their own national assessment systems. However, GBC's role as a forum and catalyst for change has taken on greater importance as researchers and practitioners continue to wrestle with the most difficult issues in building performance assessment.

• sustainability, environment

1. Assessment of the technical potential for achieving net zero-energy buildings in the commercial sector
2. Building environmental assessment methods: applications and development trends
3. Contrasting the capabilities of building energy performance simulation programs
4. EnergyPlus: creating a new-generation building energy simulation program
5. Zero Energy Buildings: A Critical Look at the Definition