Table 1 Set of benefit criteria used to select the set of mutually complementary uses for the Boyen Fortress in this study

C₁ Economic benefits

Benefits obtained thanks to returning neglected and abandoned historical buildings to use through adapting them to a new form of use, which can lead to: an increase in property value, the generation of income through using the buildings in economic activity. (Original definition)

C₂ Benefits to society

Benefits obtained thanks to reinforcing the feeling of identity and national integrity (the emotional bond between a society and historical buildings as a testament of a past period), providing a sense of safety by appropriating abandoned buildings that fall prey to vandalism, uncontrolled occupancy and converting them to purposes that are beneficial to society [49, 50]

C₃ Benefits associated with the protection of the environment

These benefits are possible to obtain as a result of extending the life-cycle of the material substance of historical buildings. They are obtained by limiting construction waste, reducing energy consumption, limiting the emission of harmful substances. They are thus measurable benefits that cannot be obtained when constructing new buildings. The protection of the environment is also affected by the potential improvement of the energy effectiveness of historical buildings during occupancy. (Original definition)

C₄ Benefits associated with the protection of cultural heritage

Benefits associated with the protection of cultural heritage are the result of preserving and restoring the past cultural characteristics of historical buildings and their popularisation. Additional beneficial factors concerning cultural heritage are linked with the knowledge that can be gained during the process of the refurbishment of historical buildings which in turn leads to the obtaining of broader knowledge of buildings and increasing the amount of experience of the architectural conservation community [49, 50]

C₅ Architectural benefits

Benefits associated with the architectural and construction-related aspects of the adaptation of buildings which affect their capacity in terms of utility and installations—making it possible to make full use of the buildings. These benefits affect the functional effectiveness of the buildings and their comfort of use. (Original definition)