TR190: The Need to Measure the Guidance Afforded by Design Strategies

Performance-based design processes are explorations guided by objectives and analyses of alternatives. Historically, building design teams have relied on precedent-based strategies to guide limited and informal exploration. Today they use more advanced strategies to guide more systematic and extensive explorations. I define design Guidance as the relative impact of strategy on exploration for a given challenge. As strategies are implemented or proposed, the need arises to measure and compare the Guidance provided by competing strategies on different challenges to support their selection and improvement. Design theory lacks precise definition and metrics for design processes and the Guidance achieved. This research addresses the questions:
How can we measure the Guidance of a design process? More specifically, how can we assess the challenges addressed, strategies implemented, and explorations executed?

I use building energy-efficiency as the domain of the study. The larger opportunity is to provide greater Guidance across objectives. Through case studies, I identify the problem. Through literature review I synthesize a framework and set of metrics. I develop the Design Exploration Assessment Methodology (DEAM) to support the comparison of Guidance across design processes. Using laboratory testing with professional designers, I evaluate explorations afforded by six strategies with respect to two challenges (renovation and new construction of a mid-rise office building). Experimental findings suggest to the order of design strategiesí ability to improve exploration from worst to best is: random guessing, tacit knowledge, point analysis, combined point and trend analysis, trend analysis alone, and full analysis. These results question the proposition that more data provide better Guidance. I conclude by adding process cost to my metrics and assessing the value of information generated by various strategies relative to challenge.

The contributions of this research are the metrics, DEAM, and the evaluation of design processes. I provide evidence that Guidance can be quantitatively assessed. I demonstrate power by measuring and comparing Guidance of strategies on a challenge. I demonstrate generality across a range of strategies and challenges. Initial findings show advanced strategies support better exploration and suggest further development of such strategies. The value of information generated, however, varies. This work motivates further research to provide greater understanding of the relative value of individual strategies to specific challenges.