4. Contributions of cases to sustainable development and rehabilitation of the building and the nearby built environment

Expanding damage to historic buildings because of natural changes, disasters, social, economic, cultural, and even political transformations, as well as the growth of the functional requirements and user expectations make the rehabilitation of old buildings in the form of new additions and adaptive reuse critical [35]. Thus, as Torres (p. 6) states, by reusing existing buildings, it becomes both possible to preserve the history and natural resources as well, by providing historic, economic, and sustainable contribution [6]. Kóródy and Vukoszávlyev, also, emphasize the importance of building rehabilitations in environmental, economic, and social responsibility, such that with their fewer new additions, and without demolition, rehabilitation projects both save energy, improve functional use, and "contribute to the local community's consciousness" [14]. Similarly, The Declaration of Amsterdam (1975) states that rehabilitation of old monuments is less costly than new construction and "social costs" are to be taken into account while deciding which one to choose [45]." Yüceer (p. 90) explains the economic value as "the potential of building for the satisfaction of maintenance expenses and for extra income with the financial gain in its present situation [8]."

When our cases are evaluated in that context, Cengel Khan, Cukur Khan, and Zağfiran Khan clearly exhibit economic, environmental, and social value with their new compatible additions and income generating new functions. Adaptation of those former khan buildings to museums and a boutique hotel with shops, café, and restaurant facilities increased the financial value of the buildings, and at the same time, both initiated a fine socio-cultural precinct in this part of Ulus district and brought new job opportunities back to this once intensively used buildings. Those cases, with their new use also demonstrate the importance of functional change and need for modernization for sustainability, as well as reveal the role of heritage conservation in urban revitalization. Such that they became important meeting and visiting points in the area attracting both local and international tourists, thus positively increased the quality of the vicinity and contributed to the economic, cultural, and social development of the local community.

Among the five case study buildings of this research, Hacı Bayram-ı Veli Mosque and Kursunlu Mosque still survive their functional continuity, though found incompatible according to international standards in terms of their new additions. Cengel Khan, Cukur Khan, and Zağfiran Khan were given a new function in order to meet the requirements of contemporary conditions with new exterior additions and interior alterations. In all cases, they positively contribute to the historical continuity and thus to the sustainability of heritage buildings, and urban fabric since they are still alive and can be transferred to next generations. Especially the compatible cases demonstrate that adaptive reuse of historic buildings can make them sustainable places linking the past with the present, as well as preserving their historic character. Also, considering the construction waste and cost, adaptation of historic buildings into new uses or retaining their original uses is also important in terms of economic and environmental point of view [61]. In all cases of this research, since they are still used in their original function or with their new functions by the attachment of new additions, instead of constructing new ones, construction wastes are reduced, and sustainability is increased. In addition, escalator, elevator, and handicapped lift attachments during their rehabilitations gave

way to accessibility of physically disabled as part of social responsibility of sustainability. Hence, the cases presented in this research justify the importance of compatible new additions and adaptive reuse and at the same time, exemplify their contributions to sustainable development.
