COMPUTATIONALLY OPTIMIZING GROSS FLOOR AREA WITHIN LOCAL ZONING CONSTRAINTS
Published by Alison Lam, Madeleine Sung, Stephen Zimmerer, Myungju Ko, and Zihao Zhang
Introduction
When designing for clients in high-density cities, an architect’s top priority is typically maximizing their building’s gross floor area while staying within the size constraints provided by local zoning codes. Maximizing gross floor area (GFA) enables the client, typically a developer, to optimize profits by maximizing the building’s leasable space. Local zoning codes typically provide constraints for a building’s maximum floor area ratio (FAR), height, and setback from site boundary, as well as further setbacks determined by environmental parameters.
Often, the architect’s schematic design process is performed in tandem with analysis of these objectives and constraints. The architect develops a building massing and then analyzes the scheme’s gross floor area and compliance with zoning code. This process is then repeated multiple times as the architect iterates different spatial layouts, refining and rejecting each as they search for the scheme that maximizes GFA within the constraints provided by zoning code.
Our team asked how automation can assist and expedite this process, hypothesizing that the computer can replace the architect in performing these first iterations and analyses. Using generative design, the computer can develop multiple design iterations that meet the constraints provided by zoning code, and then select among these iterations to determine a massing that maximizes gross floor area. This massing scheme can then be developed and refined by the hand of the architect.
In our model, the computer maximizes gross floor area within zoning constraints provided in the form of FAR limits, setback requirements, height limits, site coverage limits, and limits provided by the sky exposure plane. Our model uses Rhino with Grasshopper and Discover to generate massing models computationally that can then be developed by the hand of the designer. Our project uses a site in Seoul as a case study, but the constraints provided could be retrofitted to any site globally by inputting the site boundary, represented by a simple polyline, into a rhino model and then plugging the setback requirements, building height limits, site coverage limits, maximum FAR, and environmental setbacks into the Grasshopper model.
Methodology
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