A performance-based design and delivery process

Abstract

The emergence of low energy and Zero Net Energy (ZNE) building performance requirements combined with a growing array of human-factors objectives for light is driving a reversal of the conventional process of design and performance analysis. Rather than using a predetermined design as a starting point for analysis, practitioners and researchers are exploring how performance requirements can be used to identify promising solutions among multiple early-stage design alternatives. In an ideal case, exploration begins in the earliest stages of conceptual design, enabled using iterative, simulation-based analysis and informed by emerging “form-finding” workflows. In a conventional design process, energy/environmental analysis tools are rarely used to inform design decision-making in early stages of design, if at all. Rather, analysis occurs after design development, often for code-compliance purposes or to obtain green building certification. Consequently, feedback from analysis cannot be usefully incorporated into changes to the project that may improve comfort and energy efficiency. Because the largest impacts on project performance are generally established by decisions made in early stages of design, it is critical for performance evaluation to be integrated into the conceptual and schematic phases of design, where significant changes can be made without large impacts on project cost or schedule. Furthermore, decision-making about design doesn’t stop at the construction documentation stage but may continue through ongoing value engineering, construction, outfitting and commissioning of the final building. It may even continue to the stage where new occupants experience the space and learn how it is designed to support their work. These activities can be facilitated by the use of various types and scales of physical mockups, beginning early in design schematics and continuing into the construction phase to fine tune the interactions between a variety of integrated systems, their controls and the building’s occupants. Whole-building performance specifications, building energy benchmarking and disclosure requirements, outcome based codes and energy-performance-based procurement add additional incentive for design teams to seek mechanisms for reliable, performance feedback throughout all stages of design and project delivery. Climate also plays a critical role in the performance-based design process. In addition to the integration of on-site energy harvesting technologies, projects targeting low or ZNE outcomes often implement passive environmental control strategies (e.g. solar control, natural ventilation, thermally charged/discharged mass, daylighting), which must be carefully designed in response to local climate and context. Therefore, simulation tools must be capable of reliably modeling the effects of the local climate and urban context as well as the behavior of passive systems and occupant impacts. Finally, the shift towards environmentally responsive design strategies places a renewed focus on the role of building occupants in project performance, both in terms of long-term acceptance of comfort conditions in more dynamic indoor environments, as well as in terms of occupant interaction with the building energy concept.