New ASHRAE Guideline 0.2-2015, Commissioning Process for Existing Building Systems and Assemblies, is the comprehensive description of a systematic quality-oriented process that improves the performance and sustainability of existing facilities. This road map includes planning, assessing, investigating, implementing, verifying, and documenting performance to meet defined and optimized operational requirements. The step-by-step process guides owners and facility managers through the process of getting the best effectiveness from their facility for the lowest investment and provides the tools to ensure those benefits last for the life of the building. This guideline was developed by experienced industry practitioners and includes best practices developed through years of successful facility improvements. Guideline 0.2 is intended for use by owners, facility decision makers and commissioning providers who are focused on optimizing the operation of their facilities and systems to achieve specific goals as identified in the Owner's "Current Facility Requirements."