This paper consists of two methodological parts as follows:
The first part is a descriptive approach adopted to obtain information on the definition of adaptive reuse based on a review of the literature, beliefs, procedures, and experiences of stakeholders involved in the decision-making process related to adaptive reuse, citing local experiences about reuse in particular in the Erbil and Kirkuk citadels. The second part is divided into two steps:
- Conducting a field study and visiting the site to collect information about the place and the building such as plans, dimensions, age of the building, photos...etc.
- Applying Adaptive Reuse Potentiality (ARP) model on the Koya Qishla: conducting an interview with the archaeologists and filling a form by them that includes a set of questions related to the physical life and the obsolescence of the building, and then entering it with three specialized mathematical equations to get the value of (ARP). The resulted value will be compared with the standard in the model to see if the building can be reused or not.
Adaptive Reuse
The approach to building reuse and adaptation has become a growing trend over the past decade. Buildings of historical interest often undergo adaptive reuse, although this can be a challenging and costly experience at the same time for developers and owners due to heritage and preservation requirements. In some cases, adaptive reuse may be the only way in which a building's structure and form can be properly taken care of, revealed, or interpreted while optimizing the use of its new function. Increasing a building's life through reuse can diminish materials, transportation, energy consumption, and pollution, thus making a noteworthy and effective contribution to the sustainability of historic buildings and their preservation from demolition and collapse [10,11].
According to Langston & Shen [8] adaptive reuse refers to the process of reusing an old site or building for a purpose other than which it was built or designed for. It is regarded as a basic factor in the process of conservation the minimization of an urban extension. Yet, the distinction between renovation, facadism, and adaptive reuse is difficult and controversial. It can be considered as a compromise between demolition and historic preservation. Adaptive reuse handles the issues of heritage and conservation policies. As progress in technology, politics, and economics moves faster than the built environment, old buildings become inappropriate for their programmatic requirements, sustainable options for the reclamation of sites is adaptive reuse. When considering a building for adaptive reuse it is essential to examine the following issues [17]:
- Building layout structure and its capacity to accommodate the required functions and spaces.
- The energy efficiency of the building’s windows, walls, and roof.
- Building capabilities to meet building, safety, health, and accessibility requirements.
- The condition of the sanitary, mechanical and electrical systems and their capacity for modification.
- The presence of hazardous materials.
- The ability of the site and the building to provide a safe and secure environment.
- Convenience and safety of the building location.
Despite the evidence indicating that adaptive reuse has significant long-term benefits to be available to owners and developers, the decision-making process is tied to whether or not the building is reused.
3.1.1Criteria for Adaptive Reuse
The decision on whether to demolish a certain building due to economic reasons or to conserve and reuse it depends on some criteria including [15,18].
- The importance of the use of the site by the residents or the visitors. This importance reflects the societal value of such a site.
- The potentiality of reusing a specific site, the physical condition of the site and its suitability for future use, the character of the existing site in terms of the suggested reuse.
- The historical significance of the site, in terms of the role of the site in the community's understanding of the past and both the physicality of the area and the streetscape.
- The environmental conditions of the site, whether the site is appropriate climatically or suitable for the suggested environmental work required in the site.
Local Examples of Adaptive Reuse
Erbil Citadel
It is about 70 km away from Koya city (the study area). Erbil citadel is one of the oldest continuously inhabited urban sites in the world with continuous occupation dating back about 6000 years. Through the centuries, it was considered a notable stop on the ancient "Royal Road". The citadel occupies an area of 10.2 hectares on an artificial elliptical earthen mound about 32 meters above city level and thus becomes a prominent landmark and is considered the crown of Erbil, the capital of Kurdistan Region/Iraq. The citadel town consisting of traditional courtyard houses and a few public buildings accessed through narrow, winding alleys surrounded by adjacent houses generate its fortified perimeter wall [19].
It has been in continuous decline since the beginning of the 20th century, as lack of services, narrow and unsanitary alleys, inaccessible cars, and a growing impression of old-fashioned and inconvenient, prompted prominent wealthy families to live at the foot of the citadel leaving abandoned houses to be occupied by refugees. In 2006, the residents of the castle were obliged to leave their houses when Kurdistan Regional Government decided to preserve and revive the castle. In 2007, the High Commission for Erbil Citadel Revitalization (HCECR) founded the Erbil Citadel Revitalization Project in cooperation with UNESCO [20].
The revitalization of Erbil Citadel is approached through the concept of adaptive reuse as the core strategy for a culturally-driven revitalization [21]. The adaptive reuse of the Erbil citadel has mainly concentrated on the issue of allotting new uses to each building and the citadel as a whole. In this project the new use was highlighted to be in keeping with the spirit of the original use to guide the identification of the new use of each building, the character and value of the building, the technical and practical suitability of the building in terms of available space, adaptability, location, vehicular access, and finally, the social and economic context and sustainability of its management framework (Fig. 1). As for the citadel as a whole, the allocation of new uses is inspired by the divisions of the historical citadel district, where the Saray district was allocated for cultural uses, while the Takya district was allocated for tourist use, where its center was allocated a place for project management, and the Topkhana district was allocated for predominant residential use [19].
Kirkuk Citadel
It is about 160 km away from Koya city (the study area). Many tablets and other relics were found in the city dating back to 2600 BC related to the Sumerian civilization[22]. Kirkuk in history was only the fortified city area (Kirkuk Citadel), and this identity has been preserved for a long time. Hedges lost their importance in the region during the fifteenth century and settlement began to spread outside the hedges. Settlements began outside the citadel in later periods due to the absence of political and social stability, as the region was the site of long-term disputes between the Ottomans and the Iranians, these reasons delayed its stability until the late eighteenth century [23,24].
The idea of the citadel started with the need to protect against the assaults of enemies, so it was surrounded by huge hedges. As for the Kirkuk citadel, hedges have not survived in the urban landscape to this day. The silhouette of the citadel consists of residential buildings, although the two northern corners of the rectangular citadel were excavated by the Kirkuk Department of Antiquities and Heritage, which were built of tuff. Other parts of the citadel may have remained under the foundation of the houses which had been built across the citadel boundary to form the new general shape of the elevation. The invention of gunpowder rendered the traditional wall of the fort useless especially during the fifteenth century, and thus during that time the citadel wall was neglected which prompted the wealthy people to build their houses on top of the old wall taking advantage of the wonderful view they would get from there. As a result, the citadel came to look more like a residential area on a hill than a fortress with a defensive wall. Kirkuk Citadel has four gates, of which only the “Topkapi” gate, constructed in 1882, remains [23,25].
Mokhtar and Korumaz [25] proposed that the first step to creating new functions for Kirkuk Citadel is to identify the reasons for its reuse. It is noted historically that the creation of new requirements and the consequential functional improvements make most of the citadel buildings weak against functional obsolescence. This is due to many factors including cultural, historical, environmental, and economic ones. There is a need for a reconsideration of the building due to environmental changes. For example, the functions of some houses located in the commercial areas of Kirkuk should be changed in that the function of the surrounding area has become a commercial one while only these houses are residential such as the remaining ‘Khanaqa’ house on the other side of the citadel, (Fig. 2).
Adaptive Reuse Potential (ARP) Model
The Adaptive Reuse Potential (ARP) model was developed by Professor Craig Langston in 2008 to help transform traditional ownership stake decision-making processes for more sustainable strategies, practices, and outcomes, by identifying and categorizing the adaptive reuse potential of existing buildings. The main requirements for this model are an estimate of the expected physical life of the building (in years), and the age of the current building (in years). It can be applied in all countries and all types of buildings [5,8].
It also requires an assessment of obsolescence (economic, physical, functional, social, technological, and legal) of the building. Obsolescence is provided as a suitable method of reducing the expected physical life to objectively calculate the useful life of a building. In the past, it was difficult to predict the useful (effective) life of a building [26], so this model uses the following types of obsolescence to predict the useful life of any building [8]. Its application was first demonstrated in a real case study in Hong Kong. It provides a conceptual framework - at the level of strategic management - for assessing the potential for adaptive reuse in existing buildings.
Using equations 1, 2, and 3, the value of ARP is calculated, since the useful life can be determined from Equation (1), Equation (2) provides a line of increasing ARP, and Equation (3) provides a line of decreasing ARP. The high potential for adaptive reuse will be considered when ARP values are above 50, while ARP values in the range 20-49 show (moderate potential), and values less than 20 show (low potential). An ARP value of 0 means (no potential). When ELu and ELb are equal, it means that the maximum possible value of ARP is generated for that phase of the building life cycle.
Where: Lp = physical life in years, O1, physical obsolescence, O2, economic obsolescence, O3, functional obsolescence, O4, technical obsolescence, O5, social obsolescence, O6 denotes legal obsolescence.
Where: Elu = effective useful life in years, ELb for effective building age in years.
Building Obsolescence
Like other assets, buildings can become obsolete over time. Buildings deteriorate and become obsolete with age. The operational life of a building, which is a reflection of its structural adequacy, is greatly minimized by obsolescence causing a useful life less than the expected physical one. Obsolescence can be described as constituting one or more of the following attributes [4,5,8,27,28]:
A. Physical obsolescence: Over time, due to the accelerated deterioration, all buildings are subjected to natural erosion, leading to a slowdown and weakness in their physical performance. Measurement of physical obsolescence related to maintenance policy and performance. The useful life is effectively reduced according to a specific scale as shown in Table 1:
Table 1The scale of reducing the useful life of buildings due to physical obsolescence
0% reduction
|
For the buildings with a high maintenance budget
|
10% reduction
|
For the buildings with a normal maintenance budget
|
20% reduction
|
For the buildings with a low maintenance budget
|
B. Economic obsolescence: It’s a measurement related to the location of a building in a city center or central business district. The useful life of the building is effectively reduced according to this measure as shown in Table 2:
Table 2The scale of reducing the useful life of buildings due to economic obsolescence
0% reduction
|
For the buildings sited in an area of high population density
|
10% reduction
|
For the buildings sited in an area with average population density
|
20% reduction
|
For the buildings sited in an area of low population density
|
C. Functional obsolescence: The originally designed function of the building can be changed according to the potential change in the owner's goals and needs. Measuring functional obsolescence is related to the flexibility inherent in building design. The useful life of the building is effectively reduced according to this measure as shown in Table 3:
Table 3 The scale of reducing the useful life of buildings due to functional obsolescence
0% reduction
|
For the buildings with low flexibility
|
10% reduction
|
For the buildings with average flexibility
|
20% reduction
|
For the buildings with high flexibility.
|
D. Technological obsolescence: The use of high levels of energy in the building to provide comfort to the user leads to effectively reducing its useful life. Measuring technological obsolescence is related to the building's use of operational energy. The useful life of a building is effectively reduced according to this scale as shown in Table 4:
Table 4 The scale of reducing the useful life of buildings due to technological obsolescence
0%reduction
|
For the buildings with low energy demand
|
10%reduction
|
For the buildings with conventional operating energy performance
|
20%reduction
|
For the buildings with intense energy demand.
|
E. Social obsolescence: If the feasibility of the building depends on external income, this will effectively reduce its useful life. The measure of social obsolescence is related to the relationship between ownership and the function of a building. The useful life of a building is effectively reduced according to this measure as shown in Table 5:
Table 5The scale of reducing the useful life of buildings due to social obsolescence
0% reduction
|
For the buildings with fully owned and occupied space
|
10% reduction
|
For the buildings with balanced rent and ownership
|
20% reduction
|
For the buildings with fully rented space
|
F. Legal obsolescence: If the building is designed and constructed with a low level of execution, this leads to a reduction in its useful life. Measuring legal obsolescence is related to the quality of the original design. The useful life of a building is effectively reduced according to this metric as shown in Table 6:
Table 6 The scale of reducing the useful life of buildings due to social obsolescence
0% reduction
|
For the buildings designed and constructed according to a high-quality standard
|
10% reduction
|
For the buildings designed and constructed according to an average quality standard
|
20% reduction
|
For the buildings designed and constructed according to low-quality standards
|
Koya City (Study Area) and the Case of Qishla Castle
Koy Sanjaq, also called (Koya in Kurdish), is one of the ancient cities in the Iraqi Kurdistan region. It is a town and district about 70 km east of Erbil city, characterized by the terrain of its lands, as it is located between the two lofty mountains of Haibat-Sultan and Bawaji. The city has a long history, as it contains many archaeological sites and heritage buildings, such as Koya Qaysari, which was built by Haji Abdullah Haji Mustafa Miskeen in 1904 AD in the city center, as well as its great mosque. After the Chaldyran War in 1514 AD, Kurdistan was divided between the Ottoman and Safavid states, and as a result, the city of Koya came under the rule of the Ottomans. Qishla Castle is located northwest of the city of Koya. There are two opinions about its history, the first indicates that it dates back to the Mamluk era, while the second says that it was built by Midhat Pasha, the Ottoman ruler of Baghdad (between 1869 and 1872 AD), who was interested in establishing fortresses and military schools in the mountainous regions of the Kurdistan Region of Iraq for defensive reasons against their Safavids opponents [29-31], (Fig. 3).
Description of the Qishla Castle (Case Study)
The word Qishla is originally Turkish, taken from the verb qishlaq, meaning the scarf in which soldiers stay in the winter. The castle is semi-square in shape and is built on a hill 22 meters high from the city of Koya (Fig. 4). The building houses the military factory which has 4 towers in the corners and is surrounded by high walls for better protection. 88 m * 90 m two-story plan layout, the ground floor now has a large square garden like the courtyard but in the past, it was a training area for soldiers, the first floor of the castle contains several rooms. The building is completely opened from the inside and connected to the outside by two entrances along with a large number of small openings for war purposes [29].
Description of the Qishla Castle (Case Study)
The main walls of Qishla: The eastern wall is one of the main walls of the castle and includes the main gate. The south wall includes a set of circular windows with a diameter of 65 cm, the lower part of the wall includes 16 small openings used for throwing during wars, with many small openings in the upper part. The western wall of the castle includes a set of openings used for the same purpose, rectangular and triangular. The northern wall of the castle includes a new addition gate and several small openings of the same shapes.
The four towers: The southern tower is 8 m high and 6 m in diameter and includes four openings for throwing fire at wars. As for the eastern tower, it is 7 m high and 6 m in diameter and includes four openings for throwing fire in wars. Concerning the western tower, its height is 8 m with a diameter of 20 m from the bottom and 5 m from the top, including four openings with many rectangular windows in which fire is thrown in wars. The northern tower is 7 m high and 28 m in diameter, from bottom to top, 7 m, including four openings for casting fire in wars. All of these towers are prominent outside the main wall of the castle (Fig. 5). The walls of the towers differ from each other in thickness, and their assemblies have thick walls for defensive purposes [29].
What distinguishes the Qishleh Castle in Koya from the local castles in Kurdistan is that it was originally a defensive fortress used as a place in times of war to defend the city, in addition to military exercises for soldiers that were taking place there. Due to its small area, it does not include residential, administrative, or service facilities like the other local castles mentioned above. In simple words, Koya Qishla Castle is a defensive fortress unlike the castles of Erbil and Kirkuk which were both cities or residential castles.