To provide sustainable design criterion for a building, first of all, physical comfort and appropriate medical conditions should be met for the inhabitants. In this scope, the following items should be taken into consideration: thermal comfort (healthy climatization for indoors), visual comfort (daylight utilization, natural and artificial lightening systems), -auditory comfort (acoustic layout, noise control systems). In second step, appropriateness for ecological environmental conditions is studied; in this frame, renewable energy facilities, utilization of recycling materials, domestic water systems, waste treatment systems and sewage systems are discussed. Finally, economical factors are evaluated; in this concept, a preliminary study is held to estimate the expenditures for construction, commissioning, administration, maintenance and defects liability periods. Multi-storey social buildings as structures become widespread over main cities in the world, has been in service for more crowds rather than other types of buildings. Thus, these types of buildings can be defined as small cities in a city. Today, we need more common and serious applications on sustainable design criterion, while the silhouettes of our cities have been changing by the continuous construction of multi-storey and social buildings. This necessity carries vital importance for the future of urban development and next generations. OPTIM has been in service as an engineering and consultancy company, in projects related with buildings covering the studies as follows: concept design, architectural, structural, electrical, mechanical and fire-protection preliminary & final design, unique design, as-built study, bill of quantity, cost estimates, preparation of tender documents, tender management, project management, supervision and consultancy services at construction phase. You can find detailed information about our projects in reference portfolio related with design and consultancy services for special purpose buildings, sports facilities, hospitals, schools, dormitories, shopping zones.