T The development of the central business district (cbd) in bsd city as a new economic growth center in jakarta’s buffer zone has driven an increasing demand for multifunctional spaces that not only support business and residential activities but are also aligned with sustainability principles. rapid urbanization in this area has created various challenges, such as limited land availability, high energy consumption, rising temperatures due to the urban heat island effect, and the scarcity of green open spaces. therefore, an adaptive and efficient architectural design approach is required to address these conditions.the scope of the project includes the design of a medium-scale multifunctional building that combines business loft and apartment functions on a single site within the cbd of bsd city. the design prioritizes the flexible integration of work and living functions within a single building mass, taking into account user comfort, spatial efficiency, and the reduction of environmental impact. the conceptual approach is based on modernist principles that emphasize rational form, structural clarity, and function, which are then synergized with sustainability values through methods such as passive design, environmentally friendly materials, and the optimization of natural resources.the methods used include literature review, field observation, site analysis, regulatory study, spatial requirement analysis, and case studies of similar projects. the conceptual approach refers to the principles of modernism and sustainability. the application of modernist principles is reflected in a design that emphasizes simplicity of form and functional efficiency. the building is designed with simple geometric forms that are structurally efficient, embodying the functional aesthetics characteristic of modernist architecture. spaces are organized effectively to optimally support user activities without excessive decorative elements. the design is directed toward fulfilling functional needs rationally, with structural clarity and efficient spatial logic. meanwhile, sustainability principles are realized through passive design strategies that respond to the climate and surrounding environment. the building’s orientation is adjusted to prevailing wind directions and sunlight to maximize cross-ventilation and natural lighting, thereby reducing energy consumption. elements such as balcony shading reduce heat gain and enhance thermal comfort. the curved form of the façade and balconies responds to the sun’s path to minimize heat exposure while reinforcing the building’s visual character. this approach demonstrates the adaptability of the design to the challenges of the urban environment and climate change.