Vertical pond: design, analysis, and scaled model fabrication of a multi-material façade

Abstract Building façades play a critical role in indoor daylight regulation, yet are increasingly expected to accommodate ecological and environmental functions, particularly in the context of retrofitting existing buildings. Conventional façade systems—typically composed of materially homogeneous, layered assemblies—rarely integrate urban biodiversity and respond poorly to dynamic daylight conditions, resulting in uneven interior light distribution. This paper presents a case study of a multi-material façade that integrates daylight regulation and early-stage plant growth within a materially unified retrofit intervention. A performance-driven workflow is developed, linking annual daylight simulation, generative design, and multi-material fabrication. Daylight metrics are translated into material distribution strategies combining translucent polymers with Growlay, a porous plant-growth medium. A series of generative methods organise material transitions and cavity formation to balance water retention for plant growth with adequate interior daylight provision. Daylight performance is assessed for each resulting design using established metrics, while polymer–Growlay integration and plant-growth potential are investigated through targeted laboratory testing and preliminary seed-growth experiments. Multi-material fused deposition modelling at prototype and façade-unit scales demonstrates the geometric and material feasibility of the proposed system. Results indicate improved daylight uniformity relative to the existing façade. The study contributes empirical evidence for integrating multi-material fabrication, daylight-driven design, and bio-receptive strategies within façade retrofitting workflows, and outlines future research directions addressing durability, scalability, and broader performance validation.