Architecture and urban design projects are constantly breaking barriers of scale and complexity and continuously seek improved efficiency, sustainability, building energy performance, and cost-effectiveness. Simulation and large-scale data processing are now fundamental elements of this process. Recent advances in algorithms and computational power offer the means to address the complex dynamics of an integrated whole building system. However, scalability is a significant barrier to the realization of whole building systems tools for design, control and optimization.This position paper presents a set of techniques such as fast design parameter-space exploration, large-scale high-accuracy simulation, and integrated multi-disciplinary optimization for semi- or fully-automated designs. These techniques are extremely computing intensive, and have traditionally only been available to the research community. But, once enabled by advances in cloud computing and high performance computing, these techniques can facilitate the interactive design process resulting in improved outcomes and reduced development cycle times.