A comparison between sequential and simultaneous whole-building design optimization for building performance

This paper compares the effectivity of a sequential and a simultaneous approach, respectively derived from a conventional and an integrated whole-building design process, in the optimization of building geometry, fabric, HVAC system and its controls for building performance. It provides insights regarding theoretical benefits and limitations of the two approaches respectively based on a stage-by-stage or integrated optimization process and their comparative evaluation through a case-study office building nominally located in Nottingham (UK), modelled in Grasshopper for Rhino and simulated through EnergyPlus engine. The authors utilized a full-factorial (exhaustive) search method to explore the design space, therefore ensuring the optimality of the solutions. The resulting set of design options are postprocessed to identify Pareto-optimal designs that minimise energy demand while ensuring occupants’ thermal comfort. 12 combinations of tests have been performed based on the initial values & the order sequence of the design parameters, and eventual grouping of variables pertaining to the same building element category. It has been found that, despite the theoretical advantages of a simultaneous building optimization approach outperform any adequate design optimization effort during individual decoupled phases, the sequential search run forward and starting at the variables’ upper bound can find the same amount of Pareto-optimal solutions obtained from a simultaneous optimization while guaranteeing their “global” optimality.