Using the tool NetLogo the simulation Green Building Cycle explores how material choices shape cities beyond a building’s active use phase. The model simulates decay and environmental impact over time, highlighting that some materials can foster soil health, plant growth, and biodiversity as they break down, while others remain ecologically inactive or harmful. It frames demolition and decay as processes that can be redesigned—so the full lifecycle of buildings becomes part of sustainable urban thinking.
Project area — Old WU Vienna
As part of recent deconstruction and planning process, the former Vienna University of Economics and Business is used as the spatial base for the simulation. The building footprints provide a realistic building layout for assigning material types.
The model represents buildings as connected patches that are grouped into individual structures. Each building is assigned one dominant material—Concrete (C), Brick (B), Wood (W), Steel (S), Insulation (I), or Asbestos (A)—and classified as sustainable or unsustainable based on ecological regeneration potential rather than structural performance. Over time, sustainable materials (wood and brick) support the growth of green spaces, while unsustainable materials decay without contributing to a greener urban environment.
The Simulation interface
The interface guides the user. While Setup loads the building layout, assigns materials and labels, and prepares the growth and decay agents; Enter World lets you view the material groups; Go runs the simulation. Speed controls help to observe change, while the sliders num-growth and num-decay set how many growth (green) and decay (orange) particles are created—strongly influencing how fast greenery spreads or unsustainable patches disappear.
Final state — Building cycle transformation
The following video shows the full simulation process with the end stage of the transformation. Sustainable areas expand into a continuous green carpet, visualizing ecological regeneration emerging from material decay.