Brutalism has been one of the most controversial movements in architecture throughout history, and often misunderstood and underappreciated. Brutalist buildings are increasingly at risk of demolition despite their cultural and architectural significance. Mainstream sustainability certification systems such as LEED, BREEAM, DGNB offer valuable frameworks for environmentally conscious design but largely overlook the heritage value of existing structures. This thesis explores the question: “What are the ways of reusing a brutalist building in a more sustainable way without losing its historical characters and values?” and differently from the other building sustainability certification systems, proposes a system that also considers and cares about the heritage values of buildings.To address this gap, this research analyzed prominent sustainability assessment systems and identified their limitations regarding cultural and historical aspects.