Determination of Conservation–Reuse Parameters for Industrial Heritage Sustainability and a Decision-Making Model Proposal

Abstract

This study aims to determine the necessary parameters to ensure sustainable conservation in the adaptive reuse of industrial heritage and create a decision-making model. This study included the selection of the sample industrial heritage, determining the necessary parameters, percentage frequency analysis (PFA) of the industrial heritages in relation to the parameters, interpreting the percentage frequency results by comparing them, and developing the decision-making model. The decisions of the architectural heritage conservation organizations ICOMOS, TICCIH, and UNESCO were used to determine the conservation parameters. The reuse parameters were determined based on sustainability principles, since the adaptive reuse of historical buildings is also the subject of sustainability. The obtained parameters were converted to percentage values after being made numerically significant by two different percentage frequency analyses: conservation and reuse. Each sample used in the model was considered successful in various sources, rewarded, and praised in the literature and media. If we accept 50% as an average value, there are only four industrial heritages which are over 50% for the conservation percentage frequency analysis, but there are nine industrial heritages which are over 50% for the reuse percentage frequency analysis. On the other hand, it is written in the article that the aim is to catch 100%. Therefore, maybe it can be said that we cannot only conserve, but also fail to use. The model developed in this study will serve as a guide in establishing the conservation –use balance of project decisions as well as in objectively evaluating current practices.

1. Introduction

Since it was discovered in the 19th century that historical buildings are historical documents that should be preserved and passed down to future generations, the reasons for the deterioration of these structures have been investigated, and various preservation methods have been developed. According to studies, the most significant cause of a building’s deterioration is it being out of use [1,2]. The famous restoration theorist Gustavo Giovannoni’s principle that “in order for buildings to survive, they must be used” [3] is now referred to as the “adaptive reuse” method. Adaptive reuse is accepted as a restoration technique. Gustavo Giovannoni (1873–1947) declared five items for modern restoration theories. One of those was “in order for buildings to survive, they must be used”. It formed the basis for the Athens Conference (1931) and the Carta del Restauro/Statute of Restoration (1932) held on the international platform on conservation. The fourth paragraph of the Carta del Restauro (1932) reads “Living and standing monuments, not far from their original function and new uses in the building where necessary adaptations can be made without causing significant damage given is acceptable.” [4]. In the 21st century, this theory has been named “adaptive reuse”. This method aims to ensure the use of structures that cannot be used with their original function by equipping them with a different function. However, in adaptive reuse applications, they generally conserve only the exterior walls of the building like a shell; it is seen that the approach ruthlessly destroys elements such as the plan scheme, structural system, material, decoration program, and interior fixtures. It is almost as if the main goal of adaptive reuse has been forgotten: to preserve the historical structure. Historical buildings are historical documents with their own architectural, technical, and artistic values. Preserving only the shell of a historical document and then emptying it is an attack designed to destroy the information contained within that historical document. Furthermore, this attack is presented to society as adaptive reuse, claiming to protect the structures. However, adaptive reuse is not a business strategy or a way to create new designs; rather, it is a method developed to preserve historical structures. It preserves historical buildings and their original values such as the architecture, technique, art, landscape, close environment, spatial spirit, memory, symbolic value, and sociocultural values. Moreover, traces of its original function should be preserved and maintained. All these values should be presented in a way that informs the public. Therefore, new functions must be chosen with extra caution. Not every function is appropriate for every historical building. The most important task for those who decide on the adaptive reuse method is to find the most appropriate function for the historical building. Inappropriate functions destroy the original architectural features of historic buildings, damaging their identity and document value. In addition, it breaks the ties with the past, the immediate surroundings, settlement, society, and culture [1,2,5].

It is essential to maintain a balance between using and conserving historical buildings in adaptive reuse applications. While an overuse-oriented attitude undermines the goal of conserving historical buildings, an overprotective attitude may prevent historical buildings from being used [1,2,5]. Consequently, it is necessary to determine the parameters that should be preserved in historical buildings as well as the parameters required for the building’s use, and to achieve a balance between these parameters.

Another aspect that draws attention to adaptive reuse is that these applications are frequently mentioned in conjunction with industrial historical buildings. Industrial heritage buildings are one of the building types that have lost their original function due to technical advancements over time and are now used for adaptive reuse applications. Consequently, it is conserved as an architectural heritage and is attempting to be adapted to the present day by adaptive reuse [2,5,6].

These complexes have several advantages in terms of being modern, with features such as expanding over large areas in city centers, containing many buildings, and having wide-span spaces and practitioners. Therefore, they are typically run by private firms or local governments with programs that are comprehensive, appealing to broad populations, and generating a large financial income [6,7]. This process causes equipping industrial heritage buildings with complex and high-capacity functions, demolishing original structures that are not found suitable for the new use, and constructing new additional structures in the places of demolished structures or empty spaces. Furthermore, changing the original building’s plan schemes, constructions and materials, and facade layouts may result in the elimination of original interior equipment and machinery reflecting its technology [1,2,3,4,5,6,7].

Hence, the parameters for conservation and use must be determined to establish a conservation–use balance in the adaptive reuse applications of industrial historic places and structures. A decision-making model needed to be determined to adapt these parameters to adaptive reuse projects.

The purpose of this study is to identify which parameters are dependent on the construction of a conservation–use balance for a sustainable conservation by using the “use to protect” principle in the adaptive reuse of industrial heritage buildings. In addition, it is aimed to determine the strategies that can be used to put these parameters into practice. “Adaptive reuse” is a form of architectural conservation that focuses on both conservation and use. The adaptive reuse method is also a part of the globally emphasized concept of sustainability. Therefore, the parameters were determined by examining the published charters, reports, statements, and principles on the conservation and sustainability of internationally recognized architectural heritage. The derived parameters’ assets and impact values were aimed to be measured objectively over the reused industrial heritage structures chosen by the logistic percentage frequency method in order to be evaluated in a systematic order. The obtained values were overlapped in the conservation–use balance graph, and the conservation- and use-based approaches of adaptive reuse applications were determined. The decision-making model developed in this study will make decisions regarding the adaptive reuse of industrial heritage, and the project’s conservation and use value will be computed in percentages by entering the parameter values that the decisions affect. Thus, it will be possible to make the necessary changes during the project phase. The decision-making model is expected to function as an objective guide for architects, managers, and investors who intend to use the industrial heritage as an adaptive reuse study to balance conservation and usage.

1.1. Literature Review

Adaptive reuse of industrial heritage products has been one of the significant research topics in the scientific world in recent years. Scientists from many fields have conducted and continue to conduct significant studies on how this work should be undertaken, including architecture, statistics, geological engineering, software development, city planning, and sociology. The subject’s boundaries are quite open-ended. The boundaries range from the conservation of cultural heritage to the memories of societies, from the removal of asbestos in brown soils to tourism, from politics to economics, from clean energy to waste management, and perhaps more issues that have never been addressed before. However, since the subject of this study is to determine the necessary parameters and to propose a decision-making method to protect cultural heritage values and ensure sustainability, existing literature studies will be discussed in this regard. The parameters to be considered regarding industrial heritage are generally determined based on sustainability principles in the literature. Some authors withdrew from the study only after setting the parameters, while others used statistical methods, others benefited from software tools, and some created their own decision-making methods. However, it is noteworthy that the most-used method in the literature is the analytic hierarchy process (AHP) or that the AHP method is used as an additional method.

Ferretti et al. [8] tried to determine the suitability of the reuse of industrial buildings for touristic purposes. The parameters were compiled from the literature. Five parameters were used, and they are named quality of the context, economic activities, flexibility, accessibility, and conservation level. Multiattribute value theory (MAVT) and SWING methods were used. Mısırlısoy and Günçe [9] sought to determine the factors influencing decision-making and the best function. The parameters were compiled from the literature and they are referred to as potentials. In total, 7 main parameters and 28 sub-parameters were produced. The parameters are based on physical, economic, functional, environmental, political, social, and cultural principles. The method developed by the authors is a flowchart and the procedures to be performed are described in this diagram, respectively. Fredheim and Khalaf [10] tried to define all heritage values. The parameters were compiled from the literature and they are referred to as values. The number of parameters is more than 100. Chen et al. [11] tried to find the measurement parameters and the most suitable function according to these parameters. The parameters were compiled from the literature and they are referred to as criteria. In total, 5 main parameters and 16 sub-parameters were produced. The parameters are based on economic, social, environmental, architectural, and historical themes. They developed their own method by using the Fuzzy Delphi Method (FDM), analytic network process (ANP), and sensitivity analysis (SA) methods together. Vardopoulos [12] aimed to identify critical factors influencing local sustainable development through adaptive reuse projects and assessing the direction and level of interaction between them as a decision-making tool. The parameters were compiled from the literature. In total, 4 main parameters and 11 sub-parameters were produced. The parameters are economic, social, environmental, and cultural. Aigwi et al. [13] tried to identify parameters. The parameters were compiled from the literature. In total, 5 main parameters and 30 sub-parameters were produced. The parameters are based on economic sustainability, built-heritage preservation, sociocultural aspects, building usability, and regulatory themes. They used a performance-based framework method. Vizzari [14] worked on the parameters, the importance of these parameters, and how to decide ideal parameters from the current projects. In total, 4 main and 26 sub-parameters were determined. The parameters were compiled from the literature and these parameters are derived from the principles of urban, economic, environmental, and social sustainability. The optimized analytical hierarchy process (O-AHP) method for decision-making was used. Liu and Wang [15] aimed to identify the parameters that most affect the adaptability of heritage buildings. They defined the parameters as targets and produced 3 main parameters and 34 sub-parameters by analogy with CAS theory. Parameters were determined on architecture, spatial environment, and agent (decisionmakers and institutions) themes. They developed the adaptability of historic buildings (AHB) method. This method is developed as a combination of different methods such as the complex adaptive system (CAS), analytic hierarchy process (AHP), the structural equation model (SEM), the fuzzy evaluation, the judgment matrix, and fuzzy comprehensive evaluation. Arfa et al. [16] aimed to determine the parameters that enable choosing the ideal project. Parameters are provided from NRP Gulden Fenix Rapporten and Europa Nostra Awards specifications. In total, 6 main, 34 intermediate, and 108 sub-parameters were produced. The parameters are derived from social, architectural, cultural, environmental, economic, and innovation principles. Cucco et al. [17] aimed to determine the necessary parameters and to select the project that proposes use. The parameters are derived from 2030 SDGs and European Quality Principles. In total, 3 main, 5 intermediate, and 12 sub-parameters were produced; these parameters are based on social, cultural, and financial approaches. The analytic hierarchy process (AHP) method was used. Aydın et al. [18] aimed to determine the factors affecting the registration and the degree of effectiveness. The parameters were referred to as the criteria and were compiled from the literature. In total, 6 main and 22 sub-parameters were produced. The parameters are produced in relation to the values of the location, sociocultural environment, structure, architecture, benefit–harm situation of today’s function, and industrial heritage. Logistic regression analysis (LRA) was used as a method. Lucchi and Buda’s [19] research aimed to compare different UGRS approaches for cities and neighborhood renovation, highlighting main themes, criteria, indicators, pros, and cons to balance heritage preservation and sustainable development. The parameters are determined according to the principles of urban green rating systems (UGRS). The parameters are social, economic, environmental, societal, heritage conservation, and tourism promotion. Although the main idea is similar to this study, it is completely different in its purpose, parameters, and method. Since cultural heritage resources are based only on green certificate criteria, they are at the scale of urban planning and do not go into the details of tangible and intangible cultural heritage. Masoud and Gharipour [20] aimed to analyze and relate cultural values in the refunctioning of heritage structures. The parameters were taken from Fredheim and Khalaf’s research. There are 4 main and 10 sub-parameters. The parameters are associative, sensory, evidentiary, and functional. The ANP–Fuzzy DEMATEL framework method was used. Çakır and Edis [21] created a database to analyze the relationship between the intervention type and size with its new function in reused industrial heritage facilities. The study was produced to only investigate buildings within an industrial heritage building. The parameters consist of the functions and interventions of the buildings and have been compiled from the literature. Añibarro et al. [22] proposed 4 main and 16 sub-parameters to analyze current cases and determine the ideal use. The parameters are derived from urban, economic, environmental, and social sustainability principles. They were influenced by the publications of Vizzarri et al. and Arfa et al. Determination of the parameters and a value scale developed by them as a decision-maker. Fuzzy DEMATEL analysis was used as the method.

Wang and Zeng used the ANP and Delphi method; Fuentes used weighted sum; Di Bitonto et al. used specific algorithm for multicriteria rating; Giove et al. used Choquet integral; Paolillo et al. used multivariate analysis; Palmas et al. used GIS and AHP; Hamadouche et al. used GIS, ELECTRE and PROMETHEE; Ferretti, V. et al. used MAVT [8]. Similarly Zavadskas and Antucheviciene used TOPSIS; Giuliani et al. used MADA; Oppio et al. used CE; Mecca used ELECTRE III; Bottero et al. used PROMETHEE, NAIADE and MAVT, AHP and SWOT in different 3 researches, Della Spina used AHP and EVAMIX; Vizzarri C. et al. used 0-AHP [14]. These researches produced their parameters from the sustainability principles in the literature and it is possible to expand this list.

The parameters used by the researchers are very diverse and sometimes difficult to understand, and the methods they use are professional statistics and software programs. On the other hand, investors, producers, regulators, and users are the decision-making actors in industrial heritage reuse applications. Investors can be a company, government, municipality, various government agencies, and financial institutions. Producers are professionals such as architects, designers, engineers, and restoration specialists. Regulators are government authorities that decide on regulations regarding conservation and restoration projects, as well as giving prior approval and control projects. Users are the potential users of the buildings and current stakeholders in the area, namely the public [9].

The point to be considered here and overlooked in professional research is whether the decision-making actors can use the above-mentioned statistical and software methods. The methods produced in all research are valuable. In fact, researchers are frequently trying to achieve perfection by using more than one method in succession. However, what is the probability that the people making the decisions have studied statistics or software and are qualified to use these tools? Additionally, decision-making actors from four distinct classes must collaborate to interpret the parameters and use the same decision-making methods together. Because the method created is flawless but demands professionalism, it means that the method cannot be applied in real-world situations.

The method created should be one that is applicable to general mathematics, social, and cultural information, appeals to everyone, is simple, understandable, quick, and does not require a lot of time or overwhelming details.

The specific details can then be resolved with the help of the professionals in the relevant professions after the decision data from four different classes have made a joint decision. It will vary a lot from which professional to which industrial heritage and when to seek help. For instance, environmental engineers would be called upon to remove any asbestos from the floor; mechanical engineers would be called upon to maintain and repair any production machinery; and restoration specialist architects would be called upon to repair any damaged buildings. It is possible to reproduce these examples, but it is not possible to analyze them all with professional programs. The most important aspect of restoration science is that the buildings are full of many unknown and unseen secrets until the excavation and scraping works.

1.2. Differences and Uniqueness of the Study compared to Previous Studies

• When the literature was reviewed, it was discovered that in the last 20 years, many parameter definitions and function decision studies have been carried out on the adaptive reuse of industrial heritage. However, previous studies were based on complex statistics and software studies and were aimed at professionals. This study, on the other hand, aimed to develop a simple but informative method that can be understood by everyone and guides in making the right decisions, based on the use of the main decision-makers consisting of investor–producer–regulator–user actors in the adaptive reuse of the industrial heritage. Therefore, it has been developed to be used with basic mathematics, social, and general cultural information.
• Prior studies mainly based their parameters on international laws, sustainability principles, certifications, and development plan items. Conservation-related parameters were occasionally not addressed at all and sometimes not sufficiently. It is very important to define the parameters that need to be protected in the adaptive reuse of industrial heritage buildings. Previous studies have not used the Nizhny Tagil and Dublin Principles published by ICOMOS (International Council on Monuments and Sites), TICCIH (The International Committee for the Conservation of the Industrial Heritage), and UNESCO’s (United Nations Educational, Scientific, and Cultural Organization) heritage definitions in their models. In this study, it has been attempted to define the conservation parameters as fully and completely as possible while handling the statutes and regulations of international conservation organizations.
• There should be a use when there is a conservation. It is also necessary to prevent the lack of sustainability of the selected function and the continuous change in function by making wrong decisions. This study has, therefore, investigated the establishment of the conservation–use balance. When a thorough literature search was conducted, it was determined that there was no study on establishing the balance between conservation and use in the adaptive reuse of industrial heritage. Therefore, this study will complete a missing piece in the literature.
• This study will ensure that the right decisions are made during both the preparation and implementation stages of industrial heritage reuse projects by developing a decision-making model that integrates both conservation and sustainability parameters under one roof.

2. Factors in Establishing the Conservation–Use Balance of Industrial Heritage

The term “industrial archeology” introduced by an article written by philologist Michael Rix in the Amateur Historian Magazine in 1955 to bring attention to idle industrial heritage places, has led managers and investors to scramble to utilize empty industrial heritage areas [23]. Sometimes, competitions are held for projects to reuse inactive industrial heritage locations, sometimes, famous architects are recruited to develop projects, and sometimes, project design work is undertaken quietly and then unveiled with large-scale advertising campaigns following implementation.

The awareness studies, particularly to conserve the industrial heritages that remained in city centers, emerged in the middle of the 20th century, and have since been replaced by discussions that the conservation is overlooked in the adaptive reuse of the inactive industrial heritages. As a result, recent academic studies have aimed to create more sustainable and protective decisions for the adaptive reuse of the industrial heritage. On the other hand, civil society organizations such as ICOMOS (International Council on Monuments and Sites) [24], TICCIH (The International Committee for the Conservation of the Industrial Heritage) [25], UNESCO (United Nations Educational, Scientific, and Cultural Organization) [26], ERIH (European Route of Industrial Heritage) [27], and DOCOMOMO (Documentation and Conservation of Buildings, Sites, and Neighborhoods of the Modern Movement) [28] are attempting to guide decision-makers about what needs to be undertaken for the use of industrial heritage structures with a more conservative approach through their charters, principles, reports, and letters of recommendation. ICOMOS works to preserve and safeguard locations with a cultural heritage. TICCIH is an international society dedicated to the study of industrial archaeology as well as the preservation, promotion, and interpretation of industrial heritage. UNESCO works to promote the identification, conservation, and preservation of cultural and natural heritage that is of exceptional value to humanity. ERIH is Europe’s industrial heritage tourism information network. DOCOMOMO is an organization devoted to the documentation and preservation of Modern Movement buildings, sites, and neighborhoods. While TICCIH and ERIH directly work on industrial heritage, ICOMOS, UNESCO, and DOCOMOMO produce different identifications in their main headings, although they also work on industrial heritage as a sub-theme.

The Nizhny Tagil Charter [29], which was developed by TICCIH in 2003, aims to state that the processes experienced in industrial structures, the machines used, locations, landscapes, all the materials, and spiritual cultural information are important. The charter’s content is divided into seven sections: “definition, values, the importance of identification, recording and research, legal protection, maintenance and conservation, education and training, presentation and interpretation” of industrial heritage. The regulation states, in the section where it defines industrial heritage, that the concept of industrial heritage includes all structures where all stages such as processing, purification, storage after the raw material arrives at the industrial heritage, and all technological residues that remain in the background such as infrastructure, transportation, and energy generation that enable these stages to be realized. Industrial heritage often includes areas dedicated for a specific function or place within the institution. If a mine is utilized in the industrial heritage, it has been assessed using the concept of industrial heritage. It has also been stated that industrial heritage includes the individuals who work in these facilities and their lives spent there. In fact, it has recognized all the structures and locations where these people live, worship, learn, and engage in other social activities as part of the industrial heritage concept.

The charter emphasizes the value of identity, memory, and tradition, as well as intangible cultural assets, in the section where it discusses the merits of industrial heritage. Then, it states “site typologies or landscapes, adds value and should be carefully assessed. Early or pioneering examples are of especial value.”

The charter’s section titled “The Importance of Identification, Recording and Research” discusses in 10 points how the documentation of industrial heritage should be performed. In contrast to previous points, the sixth point states that industrial historical machinery should be conserved in its original location during restorations. The eighth point discusses the legal infrastructure that will make it mandatory to prepare, publish, and implement leading guidelines for restoration interventions.

The charter’s section titled “Maintenance and Conservation” attempted to unveil the limits of interventions that can be made in restorations. The first point in this section states that the mainly desired thing is the continuation of the industrial heritage’s original function. The second point states that information about the industrial heritage’s construction purpose and operation process should be conserved. It is emphasized in the third point the importance of conserving all elements of the industrial heritage in its original location. The fourth point requests that the new function should follow the traces of the original function and be inspired by it. The sixth point states that “interventions should be reversible and have a minimum impact”. To summarize, the most important aspect of adaptive reuse is conserving the historical structure and the traces of its original function. Since the newly given function has no historical value, it does not need to be transferred to the future. Restoration interventions, like all conservation efforts, should be limited to the bare minimum. There should be no unnecessary intervention. It is recommended in the seventh point not to imitate structures that have not survived to the present day. The most important goal here is to avoid misleading the public with copycat structures. The ninth point mentions that the most common problem in adaptive reuse implementation is changing the plan schemes. The main production building and its additions should not be demolished, nor should the plan schemes be changed to accommodate a new function.

The second international resource on the conservation of industrial heritage is the Dublin Principles [30] published by ICOMOS in 2011. The Dublin Principles consists of 14 points. The first ten points correlate to the Nizhny Tagil Charter. However, beginning with the 11th point, even though it is only recommended in exceptional circumstances, the route away from the original architecture has been formed. Especially in the 11th point as “… Changes should be documented. Reverting to a previous known state may be acceptable under exceptional circumstances for educational purposes and must be based on thorough research and documentation. Dismantling and relocating are only acceptable in extraordinary cases when the destruction of the site is required by objectively proved overwhelming economic or social needs” and in the 12th point as “In case of prospective redundancy, decommissioning, and/or adaptation of industrial heritage sites or structures, the processes should be recorded including, for example, where components have to be demolished and machinery has to be removed” statements allow for demolition, dismantling, and transportation applications in industrial heritage buildings for various reasons. Furthermore, the approaches in the Nizhny Tagil Charter suggesting the conservation of small structures that are part of the industry besides the industrial heritage, in addition to steps stating that the plan schemes of the structures should be conserved, are not included in the Dublin Principles.

UNESCO is another resource to consult for conservation-related parameters. The UNESCO values for monuments and sites that should be conserved have been used as a guide for this study’s conservation parameters [31,32,33]. The definitions of “group value, document value, technical and technological value, historical value, ID value, symbolic value, economic value, and function value”, as defined by UNESCO, have been added to the conservation parameters established in the Nizhny Tagil Charter.

The use of industrial buildings is as important as conservation. In this direction, use is related to the structure’s sustainability and is defined by its environmental, social, and economic parameters. Niklaus Kohler [34] defined the parameters of sustainability in architecture as “environmental, social, economic”. Environmental sustainability is one of these parameters, and it intends to use available resources wisely while not causing environmental harm. Considering the environmental sustainability of architectural heritage, the most rational method is to reuse the monuments and sites that can no longer be used for their original purposes [35]. Industrial heritage areas must first be assigned as protected areas to protect the environment. Because industrial heritage areas consist of various components such as functionally interconnected building groups, landscaping, and transportation, it is necessary to preserve the relationships of these components as a whole because the demolition of buildings, disconnection of buildings, opening of new roads, and reduction in green tissue are among the most important environmental threats [36,37].

Social sustainability should also be ensured in the adaptive reuse implementations of industrial heritage areas. First and foremost, industrial heritage items are cultural assets [38]. They played an important role in the development of the Industrial Revolution and the lives of laborers. The elements in the industrial heritage site are all part of a production cycle. Therefore, these elements should be in complementary relationships in adaptive reuse. Industrial heritage is also humanity’s common heritage [39]. Consequently, the newly assigned function should provide places for people to socialize and develop social and cultural relationships. The family structures, cultures, religious beliefs, and socioeconomic conditions of the people who live in these areas should be considered. The new function should not disrupt, exclude, or isolate the existing society [40]. Necessary transportation systems from near and far should be built within the industrial heritage area, as well as necessary infrastructure for people with disabilities, older adults, and pregnant citizens. Thus, it should be accessible to everyone [41]. The identity of the period and society to which they belong is represented by industrial heritage areas. During adaptive reuse, all identity values must be protected. Values from its original function should not be removed, demolished, or destroyed from the site. Visitors should comprehend that this area is a record of an era’s manufacturing technology. Therefore, the link between the industrial heritage’s past, present, and future should not be disrupted. It should be equipped with cultural functions, and in particular, Industrial Revolution equipment should be exhibited. Interior equipment and production machinery are also important original pieces of industrial heritage. Equipment used by workers during the period when the industrial heritage was active, such as chairs, tables, and sinks, should be repaired and reused in the industrial heritage. Production machines should not be removed from the facilities, but rather exhibited in their original location. These facilities serve as memorials to their founders, employees, and residents. These people’s memories should not be erased during the process of adaptive reuse. The economic, social, and cultural needs of the new users should be fulfilled in the adaptive reuse. The industrial heritage must provide modern comfort conditions and optimal life quality [42].

Economic sustainability is also important in the adaptive reuse of the industrial heritage areas. Industrial heritage sites, like other types of heritage sites, produce tourism revenue. Since there will be less construction and use of new materials during reuse, energy efficiency will improve, and construction costs will decline. Building restoration can sometimes be more expensive than reconstruction, but when it comes to cultural heritage, economic concerns should be avoided as much as possible. As a result, there are two different gains. Buildings must be maintained and repaired to conserve the cultural heritage and the necessary space for a required function is available. Transformation processes during adaptive reuse and subsequent services will employ a large number of people. There will be significant savings in economic resources because there will be no costs for purchasing new land, lawn maintenance, constructing buildings, paving roads, or landscaping. However, waste management should also be considered. The original buildings should not be demolished, additional buildings should be built as needed, and these buildings should not be larger or taller than the main industrial heritage buildings, only the outer walls of the original buildings should be preserved, and the interior should not be completely demolished, so that all the industrial heritage’s original values are registered. Thus, architectural conservation will make a significant contribution to economic sustainability [43,44,45,46].

3. Materials and Methods

3.1. Materials

This study mainly focuses on constructing an objective method, as it aims to determine the necessary parameters and develop a decision-making model to ensure sustainable conservation in the refunctioning of industrial heritage. Since the method aims to be understandable and usable by many disciplines such as public administration centers, employers, tourism professionals, architects, engineers, and interior architects, attention has been paid to make it simple and easy to apply. If we act on the assumption that all countries experienced the Industrial Revolution, it is inevitable to think that there are many factories in the world. Therefore, it was necessary to go to the elimination method in the selection of the factories to be used in the method. As a matter of fact, the nature of the developed method brought some limitations and necessitated the determination of selection criteria.

Mentioned criteria:

• The factory is registered as an industrial heritage in its own country.
• There is an adaptive reuse.
• All project and implementation phases have been completed (to be able to clearly decide on the existence of the parameters).
• Absence of excessive destruction and excessive new construction (since it would be meaningless to analyze industrial heritages with excessive destruction and excessive new construction, these examples were also excluded from the list).
• The application has been remarkably praised in the literature and media (projects that have received awards, been selected from a competition, recruited famous architects to develop projects, and governmental master projects are included).
• Having different locations for the selected examples (the reason why different locations are preferred is to observe the differences in practices according to the countries. Additionally, it is not to be caught in the similar conservation policies of one or more countries).
• Having different functions in the selected examples (the reason for varying industries is to call into question the existence of a function-related effect. At the same time, it should not be influenced by the common outcomes of the same distinct functions).
• Access to the necessary and up-to-date data on the internet for the application of the method (adequate access to internet data has also been an important factor due to the infectious diseases that are common currently, the economic crisis, and the number of factories in the world being in the thousands).

After the exclusion process Turkey—Antalya Weaving Factory, Austria—Simmering Gasworks, Italy—Peroni Beer Factory, England—Bankside Electricity Central, Spain—Matadero Madrid Slaughterhouse, Germany—Zollverein Colliery, Holland—Vann Nelle Tobacco and Food Factory, USA—Mass Moca Textiles Factory, Canada—Distillery District Factory, and France—Orsay Train Station were the examples obtained (Figure 1).

Data collecting studies for the facilities were conducted in three stages. They were general site information, components information, and main building information. General information for the industrial site was collected. These are the original function, original ID, new ID, location, new function, construction year, refunction year, number of original buildings, number of registered buildings, number of destroyed buildings, number of refunctioning buildings, number of non-intervention buildings, and number of new constructed buildings. The components information is color scheme, sociocultural trace, landscape, and transportation. The main building information is the structure and material, facade design, interior space design, and production machines. All information that has been processed is shown in Figure 2 and Figure 3.

3.2. Method/Research Model

This study’s method is to determine the conservation parameters from the publications of the UNESCO, ICOMOS, and TICCIH organizations, to determine the parameters of use from the principles of architectural sustainability, to determine the ones that can be used in terms of the adaptive reuse of the industrial heritage for all parameters, to determine the industrial heritage samples, analysis of selected industrial heritage samples over the defined parameters, to calculate the conservation–use ratios, assessment of “protective, utilitarian, or balanced” results by overlapping the ratios on the graph, and describing the application’s use as a decision-making model (Figure 4).

3.2.1. Determination of the Parameters

This study was divided into two stages since the goal was to obtain the conservation and use parameters. The first segment determines the conservation parameters. For this, the decisions of international organizations that actively work to conserve architectural heritage have been examined. ICOMOS, TICCIH, UNESCO, ERIH, and DOCOMOMO are among these organizations. However, because these organizations have various establishment concepts, it was determined that it was required to eliminate them based on their publications. ICOMOS works on the conservation of all natural and cultural values, it also collaborated with TICCIH on the adaptive reuse of industrial heritage. UNESCO is concerned with all natural and cultural heritage and establishes the parameters that allow us to define this heritage. ERIH is an international cultural route organization focusing on industrial heritage. Therefore, its major concept is tourism-oriented and does not pursue adaptive reuse. DOCOMOMO, on the other hand, focuses on current architectural heritage items, and adaptive reuse does not directly enter its field of work. Consequently, the values defined by the ICOMOS, TICCIH, and UNESCO organizations were used when defining the conservation parameters [24,25,26,27,28].

The ICOMOS and TICCIH organizations first published the Nizhny Tagil Charter, then the Dublin Principles, to define the scope of interventions for the adaptive reuse of industrial heritage buildings. The charter is higher in the hierarchy of norms in the law than the principles. The conservation parameters were identified as “sites and monuments, landscape and transportation, facade design, plan chart, color scheme, structure and material, sociocultural values, interior equipment and machineries,” based on the Nizhny Tagil Charter due to its legal superiority. In addition, “group value, document value, memory value, technical and technological value, historical value, ID value, symbolic value, economic value and function value” which UNESCO states that a cultural property must have in order to be considered a heritage by definition, have been added to the conservation parameters determined from the Nizhny Tagil Charter [29,30,31,32,33].

As a result, industrial heritages have been divided into two categories: site areas and the main production building, which serves as the center of the production chain. The parameters for the site were determined as “sites and monuments, landscape and transportation, facade design, plan chart, color scheme, structure and material, sociocultural values”. The parameters for the main production building were determined as “plan chart, structure and material, facade design, interior equipment and machineries”.

Table 1. Conservation parameters [24,25,26,27,28,29,30,31,32,33].

Components of The Sustainable Conservation of Industrial Heritage
From Nizhny Tagil Charter
Site		Main Production Building
sites and monuments		plan chart
landscape and transportation		structure and material
color scheme of the buildings		facade design
sociocultural values		interior equipment and machineries
From UNESCO Conservation Values
group value	historical value		document value
id value			symbolic value
technical and technological value	economic value		function value

shows the parameters that were determined.

The use parameters were determined in the second stage. Since the adaptive reuse of historical buildings is also a matter of sustainability, use parameters have been defined using environmental, social, and economic aspects, all of which are components of sustainability. After multiple sources were studied, the parameters for environmental sustainability were determined as using existent architectural structures, using existent site, using existent landscape and transportation; the parameters for social sustainability were determined as cultural integrity, social relationships, environmental and societal relationships, accessibility, protection of ID, balance of past and future, cultural function, memory and sense of place, interior equipment and machines, life quality of the people; the parameters for economic sustainability were determined as bringing in tourism, energy saving and efficiency, lower operation cost, job opportunity, resource and waste management. It is considered that the resource and waste management parameter comprises sub-parameters of “building demolished, building, turning the structures into shells, conservation and registration of structures”.

Table 2. Sustainable reuse parameters [34,35,36,37,38,39,40,41,42,43,44,45,46].

Parameters of The Sustainable Reuse of Industrial Heritage
Parameters of The Environmental Sustainability of Industrial Heritage
Using existent architectural structures
Using existent site
Using existent landscape and transportation
Parameters of The Social Sustainability of Industrial Heritage
Cultural integrity
Social relationships
Environmental and societal relationships
Accessibility
Balance of past and future
New cultural function
Life quality of the people
Parameters of The Economic Sustainability of Industrial Heritage
Bringing in tourism
Energy saving and efficiency
Lower operation cost
Job opportunity
Resource and waste management: building demolished, additional building, turning the structures into shells, conservation and registration of structures

shows the determined use parameters and data sources.

3.2.2. Percentage Frequency Analysis/Data Collection Tools

Two different logistic percentage frequency analyses were conducted to examine the extent to which adaptive reused industrial heritage products are conservation- and use-oriented. In the first analysis, industrial heritage products are evaluated in relation to the conservation parameters and the conservation scores of each industrial heritage are found after the transformation. The higher the score, the more the transformation is the result of conservation decisions; the lower the score, the less the transformation is the result of conservation decisions. The industrial heritage products are evaluated in relation to the use parameters in the two studies, and the use scores of each industrial heritage are determined following the conservation. The higher the score, the more the conservation is the product of the use decisions; the lower the score, the less the conservation is the product of the use decisions. A low use score also indicates that the conservation is unlikely to be sustainable.

Due to the results of both analyses, the two dependent variables will be either “conservation-oriented or non-conservation-oriented,” and “use-oriented or non-use-oriented”. The distinctive variables indicating the existence of the parameters were coded as “Present = 2, Partially Present = 1, Absent = 0” in the models that determine the conservation and use status of the examined industrial heritage.

Scoring Chart for Conservation Parameters

Sites and Monuments

0:

The site layout is destroyed and 90–100% of the buildings are demolished.

1:

The site layout is still preserved but 50–90% of the buildings are demolished.

2:

The site layout and all buildings are preserved.

Landscape and transportation

0:

More than 50% of the surface area of the landscape and road layouts are disturbed.

1:

Less than 50% of the surface area of the landscape and road layouts are disturbed.

2:

The landscape and road layout of the area has been preserved at a rate of 90–100%.

Facade design

0:

Facade layouts of all buildings have been changed and have lost their originality.

1:

Only the characteristics of the structural elements have been changed.

2:

The originality of the facades of all buildings has been preserved.

Plan chart

0:

The plan schemes of the buildings have been completely changed.

1:

The partition wall has been demolished or added.

2:

The originality of the plan schemes of the buildings has been preserved.

Color scheme

0:

The exterior and interior colors of the buildings have been completely changed.

1:

The exterior colors of the buildings are preserved, the interior colors are changed.

2:

The exterior and interior colors of the buildings are preserved in their original form.

Structure and material

0:

The original structure and material has been completely changed.

1:

The original structure and material are hidden, not visually perceived.

2:

The original structure and material are original and legible.

Sociocultural values

0:

The memories and places of the workers are destroyed.

1:

The memories and places of the workers are changed but exhibited via image tools.

2:

The memories and places of the workers are preserved in their original place.

Interior equipment and machines

0:

All furniture and machinery are removed from the facility area.

1:

Some of the furniture and machinery are preserved, the rest are removed from the site.

2:

The furniture and all machinery from the factory are preserved in their original place.

Group value

0:

More than 50% of the facility was destroyed, production cycle is disrupted.

1:

Less than 50% of the facility was destroyed, deficiencies in production cycle.

2:

In total, 90–100% of the facility is preserved, the production cycle is fully available.

Document value

0:

Facility lost all data containing information on the operation and production cycle.

1:

Facility was preserved but lost all data specific to production system.

2:

Facility presents all architectural structures, machinery, and production information.

Historical value

0:

Historical characteristics of people, events, and process are deteriorated.

1:

Misleading historical interventions have been made regarding people, events, and processes.

2:

Historical characteristics of people, events, and processes have been preserved.

ID value

0:

Facility lost production identity; the documents show it as an industrial heritage.

1:

Facility reflects its identity only as a name, the content and function are lost.

2:

The production identity of the facility is preserved and it can be easily understood.

Economic value

0:

The sales/rent value is reduced, buildings are not used, and machines are removed.

1:

The sales/rent value is preserved, buildings are used, but machines are removed.

2:

The sales/rent value is preserved, buildings are used, and machines are preserved.

Symbolic value

0:

The symbolic values of the facility have been destroyed, removed, or ignored.

1:

Some of the symbolic values of the facility have been preserved.

2:

All the symbolic values of the facility have been preserved.

Function value

0:

The original function cannot be fulfilled. The proposed function should be long-lasting.

1:

The original function cannot be fulfilled. The new function is long-lasting.

2:

Facility can operate with its original function and new function is long-lasting.

Sustainability Parameters of Reuse

Scoring Chart for Sustainable Reuse Parameters

Using Existent Buildings

0:

Less than 50% of the number of original buildings are given a new function.

1:

More than 50% of the number of original buildings are given a new function.

2:

All the original buildings are given a new function.

Using Existent Site

0:

The original site area is divided into parts and combined with nearby areas.

1:

The original site boundaries are preserved, but they are divided into parts.

2:

The original site is preserved with its area and boundaries.

Using Existent Landscape and Transportation

0:

Less than 50% of the original landscape and road system are conserved.

1:

More than 50% of the original landscape and road system are preserved.

2:

The original landscape and road system has been preserved at a rate of 90–100%.

Cultural Integrity

0:

New function not related to original function, new functions are disconnected.

1:

New function not related to original function, new functions are interrelated.

2:

New function related to original function, new functions are interconnected.

Social Relationships

0:

New function not for socializing, is only for special occasions, purpose, and group.

1:

New function not always for socializing. Open to everyone, only for special occasions.

2:

New function is a place to socialize. You can always go and spend time there.

Environmental and Societal Relationships

0:

New function does not connect with the environment and society.

1:

New function connects only with a certain part of the environment and society.

2:

New function directly addresses the environment and society in which it is located.

Accessibility

0:

Access to the location of the facility is limited, difficult, and dangerous.

1:

Access to the location of the facility is limited but safe.

2:

Access to the location of the facility is easy, safe, and diverse.

Balance of Past and Present

0:

New function completely removes traces from facility’s original function.

1:

New function preserves the historical information of the facility but hides it.

2:

New function preserves and presents the historical information of the facility.

New Cultural Function

0:

The new function has no cultural purpose.

1:

The new function serves multiple purposes, including cultural activities.

2:

The new function was designed purely for a cultural purpose.

Life Quality of the People and the Environment

0:

New function of facility is far from being abandoned.

1:

New function will make the facility recognizable and usable.

2:

New function has features that will revitalize and improve the life.

Bringing in Tourism

0:

The new function is closed to tourism activities.

1:

The new function is open to tourism but is not qualified to join the ERIH route.

2:

The new function is open to tourism to the extent that it will join the ERIH route.

Energy Saving and Efficiency

0:

Use of clean energy, energy conservation, and efficiency not considered.

1:

The new function uses clean energy sources; it only uses the energy it produces.

2:

Clean energy sources can produce their own energy, transfer energy to the environment.

Lower Operation Cost

0:

The implementation costs will be very high, and this amount will not be returned.

1:

The implementation costs will be very high, but it will pay for itself over time.

2:

Implementation costs will not be very high, will provide significant financial returns.

Job Opportunity

0:

The new function will employ very few people.

1:

The new function will only provide employment to local people.

2:

The new function will employ many people at the national and international level.

Building Demolished

0:

New function proposes the destruction of more than 50% of the original buildings.

1:

The new function proposes the demolition of less than 50% of the original buildings.

2:

The new function preserves all the original buildings.

Additional Building

0:

The new function requires the construction of more than one new building.

1:

The new function requires contemporary additions to the original buildings.

2:

The new function does not require new building construction.

Turning the Structures into Shells

0:

New function transforms into shells, destroying interior, preserving the exterior.

1:

The new function only turns secondary buildings such as warehouses into shells.

2:

New function preserves the original buildings with all their architectural features.

Conservation and Registration of Structures

0:

The new function is decided, requested to be deregistered.

1:

The new function requires the practices of change, demolition, encrustation.

2:

The new function ensures that all buildings are registered.

The obtained values were converted into percentage calculations by using Excel tables with the help of the following formulation.

3.2.3. Formulation

This article has determined the conservation and use criteria that should be considered in industrial heritage adaptive reuse projects and applications. The way these parameters were put into practice was divided into three categories and scored on a scale of 0, 1, and 2 points. The scoring formats for the parameters are given in Section 4. However, the scoring format is roughly handled as follows:

0:

No parameter is included.

1:

Implementation of the parameter imaginatively or only in part of the facility.

2:

Implementation of the parameter with an accurate and holistic approach.

The higher the score, the more accurate and successful the decisions of the project or application. The aim is to obtain “parameter number × 2 points = total point” in newly prepared projects. The score obtained in this way will represent a 100% success.

Since the research will involve measurement and evaluation procedures unique to both conservation and use, 2 different formulas—each of which has the same working system but different numbers of parameters—have been developed. Calculating percentages of conservation and use are performed using the first and second formulas, respectively.

x = point value of an industrial heritage from each parameter

a = total parameter number

x₁ + x₂ + x₃ + x₄ +……+ x_a = the sum of the parameter scores an industrial heritage receives

The total value of a facility is divided by 2 in both formulas. The reason for dividing the sum by 2 is that in “a” number of parameters, it can detect the equivalent over “a”. On this basis, the number of parameters implemented, and their percentage value will be seen.

Formulation to Calculate Conservation Percentages

There are 16 parameters in the table where the conservation parameters are calculated. Each industrial heritage is scored according to these parameters and its total score is calculated.

$$\mathrm{Conservation}\mathrm{ratio}:\frac{\left({\mathrm{x}}_1+{\mathrm{x}}_2+{\mathrm{x}}_3\dots {\mathrm{x}}_{\mathrm{a}}\right)}{2\mathrm{a}}=\frac{\left({\mathrm{x}}_1+{\mathrm{x}}_2+{\mathrm{x}}_3\dots {\mathrm{x}}_{\mathrm{a}}\right)}{2\times 15}$$

The resulting value will be either a fractional or a decimal number. This number will show how many parameters each industrial heritage provides out of the 16 parameters.

$$\mathrm{Conservation}\mathrm{percentage}:\frac{\left({\mathrm{x}}_1+{\mathrm{x}}_2+{\mathrm{x}}_3\dots {\mathrm{x}}_{\mathrm{a}}\right)}{2\times \mathrm{a}}\times 100=\frac{\left({\mathrm{x}}_1+{\mathrm{x}}_2+{\mathrm{x}}_3\dots {\mathrm{x}}_{\mathrm{a}}\right)}{2\times 15}\times 100$$

The result of the calculation will be a value out of 100. This number will indicate the percentage of the parameters provided by an industrial heritage.

Formulation to Calculate Use Percentages

There are 18 parameters in the table where the use parameters are calculated. Each industrial heritage is scored according to these parameters and its total score is calculated.

$$\mathrm{Use}\mathrm{ratio}:\frac{\left({\mathrm{x}}_1+{\mathrm{x}}_2+{\mathrm{x}}_3\dots {\mathrm{x}}_{\mathrm{a}}\right)}{2\times \mathrm{a}}/\mathrm{a}=\frac{\left({\mathrm{x}}_1+{\mathrm{x}}_2+{\mathrm{x}}_3\dots {\mathrm{x}}_{\mathrm{a}}\right)}{2\times 18}$$

The resulting value will be either a fractional or a decimal number. This number will show how many parameters each industrial heritage provides out of the 18 parameters.

$$\mathrm{Use}\mathrm{percentage}:\frac{\left({\mathrm{x}}_1+{\mathrm{x}}_2+{\mathrm{x}}_3\dots {\mathrm{x}}_{\mathrm{a}}\right)}{2\times \mathrm{a}}\times 100=\frac{\left({\mathrm{x}}_1+{\mathrm{x}}_2+{\mathrm{x}}_3\dots {\mathrm{x}}_{\mathrm{a}}\right)}{2\times 18}\times 100$$

The result of the calculation will be a value out of 100. This number will indicate the percentage of the parameters provided by an industrial heritage.

The conservation and use percentages of each facility are arranged both in row–column order and graphically, and conservation–use ratios and equilibrium conditions are revealed in the third calculation table.

A graph depicts the percentage values of conservation and use acquired for each industrial legacy. The graph allows for examining and assessing both the conservation–use balance or imbalance in an industrial heritage’s transformation and the balance with other facilities. As an outcome of the study, this method has evolved into a decision-making model that quantitatively and rationally analyzes the conservation–use balance of reused industrial heritage and guides decisions in new projects.

4. Results

The parameters influenced by the ICOMOS, TICCIH, and UNESCO publications were analyzed in the percentage frequency analysis that determines the conservation status for the industrial heritage. The conservation percentage frequencies range from 19% to 91%. The rate of 19% indicates that the conservation parameters in the repurposed industrial heritage are minimally conserved, and the adaptive reuse practices in this industrial heritage do not exhibit a conservation approach. The 91% rate indicates that the conservation parameters in the reused industrial heritage are well conserved. The industrial heritage, with an 88% conservation rate, is both on the World Heritage List and on the ERIH route. Attention has been paid to the fact that at least one of the industrial heritages to be analyzed has these characteristics. This is carried out to observe the situation in an industrial heritage site that is considered to be protected by international organizations. The single sample, which is accepted to be protected by international organizations, has the highest value, which is one of the most important indicators of the applied percentage frequency analysis results. Adaptive reuse applications created in eight industrial heritages produced results ranging from 41% to 72%.

Table 3. Conservation percentage frequency analysis.

	FACILITY	F1	F2	F3	F4	F5	F6	F7	F8	F9	F10
ICOMOS STATES	Site and monuments	1	1	1	1	2	2	2	2	2	2
	Landscape and transportation	2	0	2	1	2	2	1	2	1	2
	Facade design	0	1	1	2	2	2	2	2	2	2
	Plan chart	0	0	0	0	1	2	2	2	2	0
	Color scheme	0	2	2	2	2	1	1	1	2	1
	Structure and material	1	1	1	2	2	2	2	2	2	2
	Sociocultural values	0	0	1	0	1	0	0	0	0	0
	Interior equipment and machines	0	0	1	0	1	2	1	0	0	0
UNESCO WORLD HERITAGE LIST	Group value	1	1	2	2	2	2	2	2	2	2
	Document value	0	1	2	1	1	2	1	1	1	1
	Function value	1	1	1	1	1	2	1	1	1	1
	Technical and technological value	0	0	1	0	1	2	1	1	1	0
	Historical value	0	1	1	1	1	2	2	1	1	1
	ID value	0	1	1	1	1	2	0	0	0	0
	Economic value	1	1	1	1	1	2	1	1	1	1
	Symbolic value	1	1	1	1	1	2	1	1	1	1
	CONSERVATION (16/16)	6.5	3	9	8	10.5	14.5	11.5	7.5	8	6.5
	PERCENTAGE VALUE (%)	41%	19%	56%	50%	66%	91%	72%	47%	50%	41%

shows the conservation percentage frequency analysis. This has demonstrated that these industrial heritages are partially aimed at conservation, yet this effort is insufficient.

The parameters from the industrial heritages’ sustainability principles were analyzed in the percentage frequency analysis that determines the use status. The use percentage frequencies ranged from 36% to 86%. The 36% rate indicates that sustainability parameters are included to a smaller extent in the reused industrial heritage and that the adaptive reuse applications made in this industrial heritage have deficiencies in terms of use. The rate of 86% indicates that the industrial heritages provide the highest level of the use parameters. Environmental and economic parameters are generally attempted to be provided in the industrial heritages, according to the use-oriented percentage frequency analysis. The presence or absence of social parameters has been found to affect the differences in the percentage frequency results. Another interesting finding is that many of the social parameters overlap with the conservation parameters. As a result, the industrial heritage with the highest use percentage frequency also has the highest conservation percentage frequency value.

Table 4. Sustainable adaptive reuse percentage frequency analysis.

FACILITY			F1	F2	F3	F4	F5	F6	F7	F8	F9	F10
ENVIRONMENTAL	Using existent buildings		2	1	2	2	2	2	2	2	2	2
	Using existent site		2	1	2	2	2	2	2	2	2	2
	Using existent landscape and transportation		2	0	2	2	2	1	2	2	1	2
SOCIAL	Cultural integrity		0	0	0	0	0	2	2	2	2	2
	Social relations		2	2	2	2	2	2	2	2	2	2
	Environment and society relations		2	2	2	2	2	2	2	2	2	2
	Accessibility		2	2	2	2	2	2	2	2	2	2
	New cultural function		2	2	2	2	2	2	2	2	2	2
	Balance of past and future		0	1	1	1	1	2	0	0	0	0
	Life quality of the people and the environment		2	2	2	2	2	2	2	2	2	2
ECONOMIC	Bringing in tourism		2	2	2	2	2	2	2	2	2	2
	Energy saving and efficiency		2	0	1	1	1	2	1	2	0	1
	Lower operation cost		2	1	1	1	1	1	1	2	1	1
	Job opportunity		1	2	1	1	1	1	2	1	2	1
	Resource and waste management	Building demolished	2	2	2	0	0	1	0	2	2	0
		Additional building	2	2	1	2	0	2	2	0	2	0
		Turning the structures into shells	2	2	2	2	0	0	0	0	0	0
		Conservation and registration of structures	1	1	1	2	1	2	2	1	1	2
USE (18/18)			10	6.5	10.5	13	12.5	15.5	13	14	10	12.5
PERCENTAGE VALUE (%)			56%	36%	58%	72%	69%	86%	72%	78%	56%	69%

shows the sustainable adaptive reuse percentage frequency analysis. The industrial heritage which has the lowest percentage frequency rate for conservation also has a low percentage frequency rate for reuse.

Comparing the percentage values obtained from the percentage frequency analyses of the industrial heritages will give the result of “conservator”, “user”, or “balanced” for the adaptive reuse application made in each industrial heritage. Two percentage frequency analyses are overlapping in the graph below. The adaptive reuse of the industrial heritages with similar percentage values is balanced. When the percentage values diverge, it indicates that the balance could not be achieved and an overprotective or overuse attitude was displayed. The approximation of both percentage frequency percentages to 100% indicates that the desired success is achieved, indicating the balance between conservation and use. In this context, the conservation and use balance of the F6-coded industrial heritage is close to perfect. F3, F5, F7, and F9 are balanced but not at the ideal level, they are more than 100% away. The F1, F2, F4, F8, and F10 facilities were not balanced (Figure 5).

5. Conclusions

Industrial buildings are a form of heritage that conveys the construction techniques and technological changes of a period in which they were documented. Adaptive reuse is the most commonly used method for transferring industrial heritage products into the future. The Nizhny Tagil Charter and the Dublin Principles have been published by the ICOMOS and TICCIH organizations to define the conservation and adaptive reuse practices of industrial heritage structures. The Nizhny Tagil Charter’s conservator attitude has been replaced by a use-oriented approach in the Dublin Principles. The clauses in the Dublin Principles that begin with “if necessary” and legitimize the “demolition, dismantling, change, transportation” practices are assumed to play a significant role in the implementations by being abused, even though they are not a necessity in the practices. Use practices that do not regard conservation have resulted in significant losses from the conservation parameters of industrial heritage and have made them unsuitable for sustainable use. Therefore, new guiding methods for the adaptive reuse of industrial heritage should be developed for the decision-makers. In particular, the Nizhny Tagil Charter emphasizes the need for guidance on this subject to be created, published, and spread.

This study aimed to create a model that will enable architects and investors who want to take the proper steps in the adaptive reuse of industrial heritage to make the right decisions from the beginning of the project. The decision-making model is divided into two stages. In the first stage, the interventions considered in the industrial heritage to be reused are associated with the conservation parameters and utilization parameters of this model. They were then digitized by percentage frequency analysis and translated to percentage values. The closer the obtained percentage rates are to 100%, the more successful it is. The results of both percentage frequency analyses are overlapped on this model’s graphical table. The higher the conservation–use balance accomplished in the project, the closer the ratios of the two percentage frequency outcomes are to each other. It is a desired aim of the project that both percentage frequency results are close to 100% and the values overlap on the graph.

The decision model operating system works within a single Excel file to work with the conservation analysis, reuse analysis, formulation, percentage comparison table, and percentage value graphic. The decision-maker completes the interventions he intends to make or makes in the project according to the model’s rating system table. When you fill out the tables, you can automatically observe the percentage conservation and reuse rates of the project in the percentage value graphic section. After filling out the tables, he will see how conservative the project is, how useful it is, and whether the balance is set up or not. The model has a refeeding function. As you change your decisions on the decisive parameters to 2, the project will develop in a positive direction (Figure 6). This decisive model can also be used in competitions. This can lead to wrong decisions being rewarded for a project. A researcher, editor, or publisher can apply this model to decide how a complete application should be included in the literature. This can prevent the misleading of younger generations and new research.

Testing only 10 industrial heritages may be considered insufficient for validating the decision-making model’s functioning. However, a lot of industrial heritages were evaluated in this study. The number of buildings owned by industrial heritage products is around 30–40 on average. Analyzing too many facilities may give more reliable results but will reduce dominance over buildings. For this reason, examining 10 industrial heritages in percentage frequency analysis was considered sufficient. Only the location and the original function remained undetermined. More examples must be investigated in this regard.

Attempting to maintain the parameters established in this study in future projects will guide architects and investors in establishing the conservation–use balance in the adaptive reuse of industrial heritage buildings. There are 16 parameters determined for conservation and 18 for use. Obviously, creating a project that incorporates a total of 34 parameters will be challenging. What the investor desires will limit the architect’s design. However, an essential aspect to note here is that the conservation and use parameters are in fact strongly associated. The diagram below clearly shows the link between the parameters (Figure 7).

Important information about 10 industrial heritages can be gathered using a model with a total of 34 parameters. The model shows that the main production buildings of the facilities have been conserved, although some of the auxiliary structures have been destroyed. Consequently, the facilities’ production cycle has been significantly disrupted. The initial plan schemes were significantly changed. Structural features such as ceilings, floor coverings, and stairs were covered, modified, or painted with modern materials. On the other hand, a more conservative attitude is displayed in the facade setups. The exterior and interior spaces of the buildings are painted in vibrant colors. All examples have modern addition(s) and they are larger than the original structures. In general, the landscape and access roads are conserved. The machines have been removed from the industrial site with only two exceptions. Sociocultural values are also one of the most neglected issues.

When we observe the actual state, we can see the same results. If we compare the highest rated, F6—Zollverein Colliery, and the lowest rated, F2—Simmering Gas Works, plants, we can see that the methodology works correctly. F6—Zollverein Colliery took 2 points from the conservation parameter as “interior equipment and machines” and from the sustainability—adaptive reuse parameter as “using existent buildings” in the score chart. F2—the Simmering Works took 0 points from “interior equipment and machines” and took 1 point from the sustainability—adaptive reuse parameter as “using existent buildings” in the score chart.

In the actual state, the F6—Zollverein Colliery industrial heritage has retained almost all the “interior equipment and machines” and it is still capable of production. There is no demolished building on the site and most of the buildings on it have been adapted to be reused as museum and social facilities. Therefore, the “interior equipment and machines” and “using existent buildings” parameters are ideal. On the other hand, F2—The Simmering Works has no machines on the site. There is no mention of “interior equipment and machines”. The famous five gasometer boilers have been dismantled including all the materials and structures. Nothing has been conserved. In total, 25 buildings were demolished, 4 buildings were converted to shells, and nearly 20 new buildings were added into the industrial heritage site.

The gasometer walls of four gasometers were converted to shells and inside of those, they were converted to residences, a shopping center, and dormitory. We can understand its industrial values from the literature reviews. Therefore, the “interior equipment and machines” parameter could not take any points and “using existent site” could take 1 point. Therefore, we can say the percentage frequency analysis (PFA) methodology of the research can be controlled by feedback, and it is running.

This model’s information rationally reveals the success or failure of a completed transformation. Therefore, researchers and authors will be able to more clearly analyze the positive and negative aspects of the industrial heritage with which they are engaged. Publications that provide accurate evaluations will also accurately educate society. Moreover, the model’s main advantage is that it provides guidance from the beginning of the design process. Architects and investors will be able to predict what they will conserve and use from the beginning by looking at the parameters. They will be able to see their mistakes while making project intervention decisions by taking measurements in the model as needed. This will prevent irreversible and inaccurate application decisions.