The project is developing an innovative wooden facade with a controlled algal biofilm as an active, bioregenerative building envelope. Through the targeted combination of surface structure, water flow, and biological growth conditions, a permanently stable biofilm is established. This contributes to cooling the building’s surroundings, purifying the air, and promoting urban biodiversity. Material development, microbiology, and architecture are integrated into a unified approach. This approach transforms the facade from passive weather protection into a functional component of urban ecology.