sustainability

Article Recyclable Architecture: Prefabricated and Recyclable Typologies

Marielle Ferreira Silva 1, Laddu Bhagya Jayasinghe 2, Daniele Waldmann 2,* and Florian Hertweck 1

1 Faculty of Humanities, Education and Social Sciences, University of Luxembourg, 4365 Esch-sur-Alzette, Luxembourg; [email protected] (M.F.S.); fl[email protected] (F.H.) 2 Faculty of Science, Technology, and Medicine, University of Luxembourg, 4365 Esch-sur-Alzette, Luxembourg; [email protected] * Correspondence: [email protected]



Received: 31 December 2019; Accepted: 10 February 2020; Published: 12 February 2020


Abstract: Buildings are being demolished without taking into the account the waste generated, and the housing shortage problem is getting more critical as cities are growing and the demand for built space and the use of resources are increasing. Architectural projects have been using prefabrication and modular systems to solve these problems. However, there is an absence of structures that can be disassembled and reused when the structure’s life ran its course. This paper presents three building prototypes of new recyclable architectural typologies: (i) a Slab prototype designed as a shelf structure where wooden housing modules can be plugged in and out, (ii) a Tower prototype allowing for an easy change of layout and use of different floors and (iii) a Demountable prototype characterized by the entire demountability of the building. These typologies combine modularity, flexibility, and disassembling to address the increasing demands for multi-use, re-usable and resource-efficient constructions. Design, drawings, plans, and 3D models are developed, tested and analyzed as a part of the research. The results show that the implementation of the recyclable architectural concept at the first design stage is feasible and realistic, and ensures the adaptation through time, increases life span, usability and the material reusability, while avoiding demolition, which in turn reduces the construction waste and, consequently, the CO2 emissions.

Keywords: recyclable architecture; disassembly; adaptation; prefabrication; modularity

1. Introduction Buildings are places where people spend most of their lives. According to the United Nations [1], 1.7 billion people, which are 23% of the world’s population, lived in a city with at least 1 million inhabitants in 2018. It is estimated that the world’s population will reach 9.8 billion people in 2050 [2] leading to a growth of high-rise building construction in cities in order to provide work and habitation spaces required by the ever growing population. Undoubtedly, the building construction industry is responsible for a significant amount of global resource consumption and demand for natural resources will increase with the population growth in the future. Apart from that, the building industry accounts for more than 50% of the global energy use and over 35% of CO2 emissions [3–5]. This implies that the building industry is having an enormous impact on the environment and is responsible for a misuse of a significant amount of natural resources and the generation of waste. Therefore, resource and waste management has become an important issue around the world. Considering the responsibility and influence the industry has on the environment, new typologies and building concepts should be designed to adapt to the posterity, where they can be upgraded, transformed, disassembled and recycled to reduce the construction material waste and increase the

Sustainability 2020, 12, 1342; doi:10.3390/su12041342 www.mdpi.com/journal/sustainability Sustainability 2020, 12, 1342 2 of 21 service life of buildings. The materials and methods used to construct a building affect the environment just as much the way they are designed to operate has a significant impact on their whole life cycle and future use [6]. Nowadays, there is an increasing effort to move towards sustainable and circular living spaces. A circular city is based on a built environment that is shared, flexible, based on a modular design, improves the quality of life of its residents and minimizes virgin material use [3]. The new ecological needs require a global and integrated way of thinking and designing in an effort to save material and energy, to care about the environment and to optimize resources in the construction [7]. The overall lifecycle of buildings has to be considered, as there is energy involved in demolition, in new construction and in building operations as well as energy generated in the process of mobility needs [8]. As an alternative to conventional building procedures, prefabrication and modular systems are adopted in the building design. The offsite manufacturing processes can offer greater accuracy, shorter construction times, safer working conditions and better value, as well as promote recycling and reduce waste [9], although it can create a monotonous landscape if not studied and explored enough. The integration of reusable and recyclable materials and components in the construction can be used for effective waste management, because it reduces the environmental impact of construction, including the depletion of natural resources, cost and energy use incurred by landfilling [10]. The use of recycled materials can save more than 60% of the initial embodied energy of buildings [11]. As well as striving to create the lightest possible structures, the future of lightweight construction must also be guided by the need to develop recycling-friendly building methods and to minimize the production of grey energy from fossil fuels [12]. The growing demand for an expandable built environment can only be met if the amount of materials used is reduced and made available for further reuse [12]. The design for disassembly (DfD) aims to reduce the consumption of materials, cost and waste in the construction, renovation and demolition and eliminate waste that cannot be reintroduced into the cycles by reducing the physical interdependence and increasing the simplification of systems. Moreover, it increases the service life of buildings, all while making them material banks for the future [12,13]. The material recovery is intended to maximize economic value and minimize environmental impacts through subsequent reusing, repairing, remanufacturing and recycling [3,13,14]. The benefits of increasing building material recycling rates from 20% to 70% are considerable, as demolition and renovation waste can account for up to 50% of waste [4]. This paper intends to present new architectural typologies which can offer solutions to reduce waste generated in construction. Applied at the early stage of the design process, disassembly concepts and prefabricated and modular systems address the issue of housing shortage, while opening the discussion about recyclable architectural concepts. Prefabricated architecture is not new, and the aspects of history in which it was most relevant often reflect today’s circumstances. Architects, engineers and contractors need to improve their understanding of the history and pragmatics of prefabrication so that they can effectively develop and implement these methods in architectural production [9]. Therefore, a documentary research methodology was applied to create a historical narrative in Section2 from the literature review on the history of prefabrication of buildings to approach recyclable buildings based on journals, books, newspapers, reposts and websites in the fields of prefabrication, recycling, architecture and construction. The history and the building projects are a reference used to develop prototypes through the research by design methodology. In order to establish a starting point, the view of eminent people in the field on the topic at hand was examined [15]. Section3 presents three conceptual building typologies and proposal models—“Slab”, “Tower” and “Demountable”—as an answer to social problems, which had been developed within the Eco-Construction for Sustainable Development (ECON4SD) research project co-funded by the European Union in partnership with the University of Luxembourg. The overall objective of this project is to strengthen capacities in sustainable construction by developing components and design models for resource and energy-efficient buildings based on construction materials such as concrete, steel and timber. The design of these three prototypes differs from other buildings as they are designed to be dismantled at the end of their service life, are highly effective spaces with a minimal footprint as well as large-scale structures with flexible and Sustainability 2020, 12, 1342 3 of 21 adaptable uses which combine individual housing with community activities and a variety of modular and prefabricated construction types. Despite different ideologies, for many academics and practitioners of architecture, the concept of recyclable architecture has remained essential to the evolution of architectural knowledge. This paper contributes to the current body of knowledge by providing a deep insight into prefabrication and modular typologies leading towards the Recyclable Architecture. The outcomes, i.e., the projects of the architectural typologies developed during this research, are intended to be implemented in cities or regions where there is a need for new construction to provide houses offering shared and public spaces while enabling the adaptation to social needs, while reducing the use of natural resources and waste generated. The projects of the buildings can be adapted to the regulations of each region keeping the same typology. For example, the buildings’ height can be changed by adding or reducing floors. In addition the Slab, Tower and Demountable prototypes and concepts are intended to serve as a guideline for other building projects and may help architects and designers, as well as decision-makers, policymakers, clients, developers and the construction industry to have a better understanding of recyclable architecture and adapt appropriate strategies to overcome the identified challenges.

2. The History of Prefabrication Towards Recyclable Buildings The concepts of modularity, disassembly, reuse, and recycling in construction are presented for a better understanding of the history of prefabrication. Modular methods are closed systems in which elements are prefabricated independently for a specific building. In addition, the modules can be assembled into complete entities by combining them in several different ways [16]. Disassembly is a process in which a product is separated into its components and/or subassemblies by nondestructive or semi destructive operations. Reuse is the use of components and modules obtained from the end-of-life products as replacement parts. Recycling is the recovery of materials from end-of-life waste products [17]. Prefabrication is a method of producing components offsite in a factory and then assembling them onsite [9,18]. It challenges architecture, bringing up the question of the authorship of a concept and singularity, and requires knowledge of production and construction methods. If architecture could suit these requirements and succeed, a difference could be made to the quality of the built environment [9]. It has been found that prefabrication increases the safety and quality of construction while reducing the time, cost, material waste and the impact on the environment [19,20]. The projects presented in this Section inspired the design concepts of the prototypes presented in this paper in Section3, using critical analysis about what could be brought to the present and work nowadays.

2.1. Prefabricated Buildings The history of prefabrication begins with Great Britain’s colonization, which required a rapid building initiative in the settlements [9]. In 1830, Henry John Manning designed the Portable Colonial Cottage, a timber and panel infill prefabricated system, for emigrants to Australia [9,18]. In the mid-1800s, William Fairbairn built four cruiseships using the techniques of the first iron steamboat. Built from riveted plates to form units, they could be assembled, disassembled, and reassembled. This technology was later transferred to build prefabricated iron plate homes. Manufacturing methods paved the way for new theories and approaches to prefabrication technology in architectural production [9]. The ideas of rationalization in architecture used later on in prefabrication started in the first half of the nineteenth century with Jean Nicolas Louis Durand and his architectural conception of symétrie, regularité and simplicité (symmetry, regularity and simplicity). The Joseph Paxton Crystal Palace is one of the earliest prefabricated buildings. It was built in London to house the Great Exhibition of 1851. After the exhibition, it was dismantled and relocated elsewhere [9]. At the turn of the twentieth century, the idea that the city and architecture are transitory and temporary has appeared in the pioneer Antonio Sant Elias’s Manifesto of Futurist Architecture in 1914. He pronounced that each generation must build its own city: “The houses will not last as long as we Sustainability 2020, 12, 1342 4 of 21 Sustainability 2020, 12, x FOR PEER REVIEW 4 of 21 do.”as we This do.” experience This experience of the rapid of the passage rapid ofpassage the time of now the leadstime now for the leads first for time the to thefirst renunciation time to the ofrenunciation the old principle of the old of Durability. principle of Besides, Durability. futuristic Besides, projects futuristic were pr designedojects were to focus designed on rationalized, to focus on mechanical,rationalized, and mechanical, industrialized and industrialized cities and high-rise cities buildings,and high-rise integrating buildings, diff integratingerent uses such different as offi usesces, houses,such as shopsoffices, and houses, public shops spaces and in the public same spaces building in [the21]. same In the building 1920s, Walter [21]. GropiusIn the 1920s, adapted Walter flat roofsGropius and adapted the loss flat of greenroofs and ground the loss was of reclaimed green grou onnd rooftops was reclaimed used as accessibleon rooftops gardens used as in accessible order to incorporategardens in order nature to intoincorporate the city nature [21]. The into evolution the city [21]. of the The flat evolution roof garden of the is flat used roof as agarden reference is used for sustainableas a reference building for sustainable today. building today. During thethe ModernistModernist movement, movement, in in 1923, 1923, Le CorbusierLe Corbusier stated, stated, “the “the house house is a machine is a machine for living” for andliving” saw and mass-produced saw mass-produced architecture architecture as the answer as the to an socialswer ills, to settingsocial ills, up asetting construction up a construction system that wassystem based that on was rationalization based on rationalization through standardization. through standardization. Although noneAlthough of Le none Corbusier’s of Le Corbusier’s buildings werebuildings constructed were employingconstructed prefabricated employing methods, prefabricated his ideas methods, about using his the ideas manufacturing about using industry the weremanufacturing common practiceindustry for were architects common of thepractice time [9for]. Inar 1932,chitects the of term the "assembledtime [9]. In house" 1932, the was term first used"assembled by Frank house" Lloyd was Wright. first used These by Frank houses Lloyd consisted Wright. of modularThese houses units consisted which became of modular the spatial units buildingwhich became blocks the defining spatial thebuilding various blocks rooms defining [9]. Wright’s the various Usonian rooms homes [9]. Wright’s of the late Usonian 1930s presented homes of the rationalization.late 1930s presented However, the rationalization. his methods never Howe variedver, much his methods from onsite never construction, varied much and from his housesonsite wereconstruction, expensive and because his houses of the were high expensive demand because for quality of the in hand-craftedhigh demand detailfor quality [9]. Following in hand-crafted some ideasdetail of[9]. Modernism, Following Richardsome ideas Buckminster of Modernism, Fuller sawRichard architecture Buckminster as an appliedFuller saw technology, architecture expressed as an inapplied terms oftechnology, energy, mathematics expressed andin terms rationality of energy, [21]. In mathematics 1928, he patented and rationality the Dymaxion [21]. house, In 1928, which he waspatented developed the Dymaxion further inhouse, 1945–1946 which intowas thedevelope “Wichitad further House” in prototype1945–1946 [into9,21 the] (see “Wichita Figure 1House”). The wordprototype “Dymaxion” [9,21] (see denotes Figure maximum 1). The word benefit “Dymaxion” for a minimum denotes energy maximum input inbenefit order for to gaina minimum control ofenergy climate input conditions in order [21 to]. gain The prototypecontrol of wasclimate fabricated conditions in aluminum [21]. The andprototype fastened was with fabricated rivets in in a hexagonalaluminum planand fastened followed with by arivets fixed in structural a hexagonal pattern. plan followed All the services by a fixed were structural grouped pattern. at the All center the core.services However, were grouped Fuller stopped at the center the production core. However, claiming Fuller that it stopped was not the ready production for large deliveriesclaiming [that9]. Init 1942,was not Walter ready Gropius for large in collaboration deliveries with[9]. In Konrad 1942, WachsmannWalter Gropius produced in collaboration the “Prepackaged with Konrad House” withWachsmann prefabricated produced wood the structure “Prepackaged and panels House” [9,22 ].with The prefabricated technique was wood also practicedstructure byand Mies panels van der[9,22]. Rohe The who technique contributed was toalso the practiced societal acceptance by Mies ofvan the der steel Rohe and who glass contributed tower using to prefabrication. the societal Theacceptance Seagram of Buildingthe steel and in New glass York tower City using is a prefab goodrication. example The of this Seagram [9,13]. Building Many of in their New parts York were City standardized,is a good example although of this the [9,13]. assembly Many process of their was parts customized, were standardized, making factory although process the cost assembly savings insignificantprocess was customized, [9]. making factory process cost savings insignificant [9].

(a) (b)

Figure 1. RichardRichard Buckminster Buckminster Fuller. Fuller. (a) Wichita (a) Wichita House, House, 1945–1946 1945–1946 [9]; (b [)9 Dymaxion]; (b) Dymaxion House project House project[16]. [16].

With soldierssoldiers returningreturning from from World World War War II II (WWII), (WWII) the, the housing housing market market rose rose inthe in the US. US. In 1946, In 1946, the federalthe federal government government of the of US the passed US passed the Veteran the Ve Emergencyteran Emergency Housing Housing Act (VEHA), Act (VEHA), giving the giving mandate the tomandate produce to 850,000produce prefabricated 850,000 prefabricated houses in houses less than in twoless than years two [9]. years William [9]. LevittWilliam benefited Levitt benefited from the VEHA;from the producing VEHA; producing homes in thehomes factory in systematizedthe factory systematized the onsite process the onsite and addedprocess a separationand added ofa constructionseparation of planningconstruction and planning execution and [9 execution]. Similar [9 to]. Levitt,Similar Jean to Levitt, Prouv Jeané produced Prouvé produced French postwar French housing.postwar housing. In Western In Western Europe, theEurope, Marshall the Marshall Plan was Plan setting was the setting stage the for stage post-WWII for post-WWII rapid growth. rapid Prouvgrowth.é worked Prouvé with worked Pierre with Jeanneret Pierre toJeanneret develop Packedto develop and demountablePacked and demountable family homes family made entirelyhomes made entirely of timber—the Pavilions were 8 × 8 and 8 × l2 meters large (see Figure 2). These designs were lightweight, quickly erectable prefabricated shelters used as a temporary housing solution.

Sustainability 2020, 12, 1342 5 of 21 of timber—the Pavilions were 8 8 and 8 l2 m large (see Figure2). These designs were lightweight, Sustainability 2020, 12, x FOR PEER REVIEW× × 5 of 21 Sustainabilityquickly erectable 2020, 12, x prefabricated FOR PEER REVIEW shelters used as a temporary housing solution. Prouvé worked5 of to21 minimize waste and maximize benefits [9,22]. The United Kingdom’s post-war housing program ProuvéProuvé worked worked to to minimize minimize waste waste and and maximize maximize benefits benefits [9,22]. [9,22]. The The United United Kingdom's Kingdom's post-war post-war mirrored the US, with the difference being that the houses were meant to be transitory, therefore housinghousing program program mirrored mirrored the the US, US, with with the the differe differencence being being that that the the houses houses were were meant meant to to be be focusing on speed instead of quality. Prefabrication was used to manufacture and erect them, utilizing transitory,transitory, therefore therefore focusing focusing on on speed speed instead instead of of quality. quality. Prefabrication Prefabrication was was used used to to manufacture manufacture factories and creating employment. All four main types of temporary bungalows were manufactured andand erect erect them, them, utilizing utilizing factories factories and and creating creating employment. employment. All All four four main main types types of of temporary temporary in the UK—the Arcon (steel frame), the Uni-Seco, the Tarran (both timber-framed) and the AIROH bungalowsbungalows were were manufactured manufactured in in the the UK—the UK—the Arco Arcon n(steel (steel frame), frame), the the Uni-Seco, Uni-Seco, the the Tarran Tarran (both (both (Aircraft Industry Research Organisation on Housing) houses [9]. timber-framed)timber-framed) and and the the AIROH AIROH (Aircraft (Aircraft Industry Industry Research Research Organisation Organisation on on Housing) Housing) houses houses [9]. [9].

(a)(a) (b)(b) Figure 2. a b FigureFigure 2. 2. JeanJean Jean Prouvé’s Prouv Prouvé’sé’s Pavillion. Pavillion. Pavillion. ( (a ())a Assembling) Assembling Assembling the the the prototype prototype prototype Pavillion, Pavillion, Pavillion, 1944 1944 1944 [23]; [23 [23];]; ( (b ())b Prefabricated Prefabricated) Prefabricated househouse type type assembly assembly diagram diagram [16]. [16 [16].]. After WWII, in 1954, many companies that began as recreational mobile trailer manufacturers AfterAfter WWII, WWII, in in 1954, 1954, many many companies companies that that began began as as recreational recreational mobile mobile trailer trailer manufacturers manufacturers shifted into producing permanent portable housing in the US. Mobile homes were built entirely as a shiftedshifted into into producing producing permanent permanent portable portable housing housing in in the the US. US. Mobile Mobile homes homes were were built built entirely entirely as as a a module on a chassis in a factory and then trucked to the site. The mobile home became a permanent modulemodule on on a achassis chassis in in a afactory factory and and then then trucked trucked to to the the site. site. The The mobile mobile home home became became a apermanent permanent housing increasing from a 2.45 m to a 3.00 meters-wide trailer, offering more space [9]. During the housinghousing increasing increasing from from a a2.45 2.45 meters meters to to a a3.00 3.00 meters-wide meters-wide trailer, trailer, offering offering more more space space [9]. [9]. During During 1950s, the idea of a mass-produced expendable component dwelling can also be seen in Ionel Schein’s thethe 1950s, 1950s, the the idea idea of of a amass-produced mass-produced expendable expendable component component dwelling dwelling can can also also be be seen seen in in Ionel Ionel prefabricated hotel units, Alison and Peter Smithson’s House of the Future at the Ideal Home exhibition Schein’sSchein’s prefabricated prefabricated hotel hotel units, units, Alison Alison and and Peter Peter Smithson’s Smithson’s House House of of the the Future Future at at the the Ideal Ideal Home Home of 1955, and the Monsanto Plastic House in Disneyland [24]. exhibitionexhibition of of 1955, 1955, and and the the Monsanto Monsanto Plastic Plastic House House in in Disneyland Disneyland [24]. [24]. In the 1960s, the contribution of Louis J. Kahn to prefabrication was revealing a material and InIn the the 1960s, 1960s, the the contribution contribution of of Louis Louis J. J.Kahn Kahn to to prefabrication prefabrication was was revealing revealing a amaterial material and and a a a system (precast columns, vierendeel girders and beams) as well as its method of construction for systemsystem (precast (precast columns, columns, vierendeel vierendeel girders girders and and be beams)ams) as as well well as as its its method method of of construction construction for for aesthetics and design [9]. During 1962–1964, the plug-in cities were set up by applying a large-scale aestheticsaesthetics and and design design [9]. [9]. During During 1962–1964, 1962–1964, the the plug plug-in-in cities cities were were set set up up by by applying applying a alarge-scale large-scale network-structure containing access-ways and essential services. The plug-in city integrated the metal network-structurenetwork-structure containing containing access-ways access-ways and and essential essential services. services. The The plug-in plug-in city city integrated integrated the the cable housing concept, a megastructure of concrete that placed removable house elements able to be metalmetal cable cable housing housing concept, concept, a amegastructure megastructure of of conc concreterete that that placed placed removable removable house house elements elements able able updated as technology moved forward and adapt with the dweller as his needs changed. The Cook’s toto be be updated updated as as technology technology moved moved forward forward and and ad adaptapt with with the the dweller dweller as as his his needs needs changed. changed. The The Housing for Charing Cross Road in 1963 and the Chalk’s Plug-In Capsule Homes in 1964 were good Cook’sCook’s Housing Housing for for Charing Charing Cross Cross Road Road in in 1963 1963 and and the the Chalk’s Chalk’s Plug-In Plug-In Capsule Capsule Homes Homes in in 1964 1964 were were examples of the plug-in houses [24], (see Figure3). goodgood examples examples of of the the plug-in plug-in houses houses [24], [24], (see (see Figure Figure 3). 3).

Figure 3. Peter Cook, Housing for Charing Cross Road, 1963 [24]. FigureFigure 3. 3. Peter Peter Cook, Cook, Housing Housing for for Charing Charing Cross Cross Road, Road, 1963 1963 [24]. [24].

AtAt the the 1967 1967 World World Expo Expo in in Montreal, Montreal, Moshe Moshe Safdie Safdie designed designed his his first first built built project project “Habitat “Habitat 67” 67” (see(see Figure Figure 4). 4). A A housing housing complex, complex, consisting consisting of of 158 158 houses, houses, was was constr constructeducted from from 354 354 modular modular reinforcedreinforced precast precast concrete concrete units units manufactured manufactured offsite. offsite. The The units units could could be be combined combined providing providing

Sustainability 2020, 12, 1342 6 of 21

At the 1967 World Expo in Montreal, Moshe Safdie designed his first built project “Habitat 67” (see Figure4). A housing complex, consisting of 158 houses, was constructed from 354 modular reinforced Sustainability 2020, 12, x FOR PEER REVIEW 6 of 21 precast concrete units manufactured offsite. The units could be combined providing different sizes for thedifferent residents. sizes Thefor the blocks residents. were too The heavy blocks to were be easily too heavy installed to be or easily relocated, installed had or too relocated, many variations, had too andmany required variations, specific and tools,required towering specific cranes tools, and towering intensive cranes labor and [9 ].intensive labor [9].

Figure 4. Moshe Safdie, Habitat 67, 1967 [[9].9]. The 1960s also brought the Japanese Metabolists’ manifesto published by Kisho Kurokawa and The 1960s also brought the Japanese Metabolists’ manifesto published by Kisho Kurokawa and others [9,21,25]. The central idea was the individual capsule— movable, prefabricated and plugged others [9,21,25]. The central idea was the individual capsule— movable, prefabricated and plugged into a structural service core. Kurokawa’s Nakagin Capsule Tower located in Tokyo is a rare remaining into a structural service core. Kurokawa’s Nakagin Capsule Tower located in Tokyo is a rare example of Japanese Metabolism. It is comprised of two interconnected concrete towers and 144 remaining example of Japanese Metabolism. It is comprised of two interconnected concrete towers individual, movable, and prefabricated capsules [9,21] (see Figure5). Ironically, the building has never and 144 individual, movable, and prefabricated capsules [9,21] (see Figure 5). Ironically, the building been changed or extracted from the core, and is deteriorated [9]. Kurokawa even claimed that his high has never been changed or extracted from the core, and is deteriorated [9]. Kurokawa even claimed technology “meta-architecture,” with its notion of natural organic life-cycles, introduced an ecological that his high technology “meta-architecture,” with its notion of natural organic life-cycles, introduced system into architecture [9,25]. an ecological system into architecture [9,25].

Figure 5. Kisho Kurokawa, Nakagin Capsule Tower, 1970–1972, Tokyo [26]. Figure 5. Kisho Kurokawa, Nakagin Capsule Tower, 1970–1972, Tokyo [26]. 2.2. Ecological and Recyclable Buildings 2.2. Ecological and Recyclable Buildings Pursuing the history of prefabrication and adding to the high-tech and Metabolism era, the concern Pursuing the history of prefabrication and adding to the high-tech and Metabolism era, the withPursuing the possibility the history of material of prefabrication depletion the and consequent adding ecologicalto the high-tech movement and startedMetabolism in 1970, era, at the concern with the possibility of material depletion the consequent ecological movement started in USconcern oil production with the peak.possibility In 1973, of anmaterial oil crisis depletio forcedn a the dramatic consequent rise in theecological price of movement energy, products started and in 1970, at the US oil production peak. In 1973, an oil crisis forced a dramatic rise in the price of energy, products and services across the entire global supply chain [27]. In 1997, the Kyoto Protocol international agreement was signed to stabilize Greenhouse Gas atmospheric concentrations to prevent dangerous interference in the climate system [28]. As a consequence, projects started to focus

Sustainability 2020, 12, 1342 7 of 21 servicesSustainability across 2020, the12, x entire FOR PEER global REVIEW supply chain [27]. In 1997, the Kyoto Protocol international agreement7 of 21 Sustainability 2020, 12, x FOR PEER REVIEW 7 of 21 was signed to stabilize Greenhouse Gas atmospheric concentrations to prevent dangerous interference on obtaining the maximum performance with the minimum of resources, which lead to the emerging inon theobtaining climate the system maximum [28]. performance As a consequence, with the projects minimum started of resources, to focus on which obtaining lead to the the maximum emerging of new architectural solutions. performanceof new architectural with the solutions. minimum of resources, which lead to the emerging of new architectural solutions. The High-rise of Homes is a theoretical project by SITE in the USA from 1981 (see Figure 6). The The High-rise High-rise of of Homes Homes is is a atheoretical theoretical project project by by SITE SITE in the in theUSA USA from from 1981 1981 (see (seeFigure Figure 6). The6). building is a vertical community of private homes supported by a steel and concrete matrix, an Thebuilding building is a isvertical a vertical community community of private of private homes homes supported supported by a by steel a steel and andconcrete concrete matrix, matrix, an alternative to the traditional housing design in the urban landscape, replaced by garden spaces and analternative alternative to the to thetraditional traditional housing housing design design in th ine urban the urban landscape, landscape, replaced replaced by garden by garden spaces spaces and personalized architectural identity [29]. Inspired by SITE, Frei Otto saw architecture as a way to andpersonalized personalized architectural architectural identity identity [29]. [29 Inspired]. Inspired by bySITE, SITE, Frei Frei Otto Otto saw saw architecture architecture as as a a way way to improve man’s living conditions in harmony with nature, which led him to investigate the question improve man’sman’s livingliving conditionsconditions in in harmony harmony with with nature, nature, which which led led him him to to investigate investigate the the question question of of ecological building and making him one of the precursors of sustainability in architecture. Through ecologicalof ecological building building and and making making him him one one of of the the precursors precursors of of sustainability sustainability inin architecture.architecture. Through the research, he arrived at a new form of natural, adaptable and flexible lightweight construction, as the research, hehe arrivedarrived atat aa newnew formform ofof natural, natural, adaptable adaptable and and flexible flexible lightweight lightweight construction, construction, as as a a way of building with minimum consumption of material, energy and economical means [11,21]. In waya way of of building building with with minimum minimum consumption consumption of of material, material, energy energy andand economicaleconomical meansmeans [[11,21].11,21]. In 1990, Otto applied these principles in the Ökohäuser (Ecological houses) in Berlin, which is a vertical 1990, Otto applied these principles in the Ökohäuser (Ecological houses) in Berlin, which is a vertical structure, composed of three residential houses with a concrete skeleton positioned on solid pillars structure, composed of three residential houses with a concrete skeleton positioned on solid pillars (see Figure 7). The inhabitants themselves customized the open and raw structure with the architect’s (see Figure7 7).). TheThe inhabitantsinhabitants themselvesthemselves customizedcustomized thethe openopen andand rawraw structurestructure withwith thethe architect’sarchitect’s support and guidance. Initially, new families were supposed to demolish the oldest and to start over support and and guidance. guidance. Initially, Initially, new new families families were were supposed supposed to demolish to demolish the oldest the oldest and andto start to startover again, but this has never been the case [30]. The project opens the discussion about flexibility, overagain, again, but this but thishas hasnever never been been the thecase case [30]. [30 The]. The project project opens opens the the discussion discussion about about flexibility, flexibility, individual housing in a community, and ecology—even though there is no guarantee that, in the end, individual housing in a community, community, and ecology—even though there is no guarantee that, in in the the end, end, it will be affordable, and the families will keep the concepts. it will be aaffordable,ffordable, andand thethe familiesfamilies willwill keepkeep thethe concepts.concepts.

Figure 6. SITE, High-rise of homes, 1981 [29]. Figure 6. SITE, High-rise of homes, 1981 [29]. [29].

Figure 7. Frei Otto, Ökohäuser, 1990, Berlin [30]. Figure 7. Frei Otto, Ökohäuser, 1990, Berlin [[30].30]. In the late 2000s, the Tiny Homes movement startedstarted in North America with the housing market In the late 2000s, the Tiny Homes movement started in North America with the housing market crash. These tiny homeshomes werewere usuallyusually 37 37 square square meters meters or or less, less, meaning meaning the the homeowners homeowners were were able able to crash. These tiny homes were usually 37 square meters or less, meaning the homeowners were able buildto build them them themselves. themselves. The The smaller smaller footprint footprint meant meant it it cost cost less, less, requiredrequired fewerfewer materials,materials, reduced to build them themselves. The smaller footprint meant it cost less, required fewer materials, reduced construction waste and was generally more energy-eenergy-efffificientcient in the long runrun toto maintain.maintain. Their low construction waste and was generally more energy-efficient in the long run to maintain. Their low energy requirements were based on solar power or other alternative forms of energy. Many were also energy requirements were based on solar power or other alternative forms of energy. Many were also built on wheeled trailer bases to make them portable. Tiny houses are symbols of a simpler lifestyle built on wheeled trailer bases to make them portable. Tiny houses are symbols of a simpler lifestyle where “less is more” [31]. where “less is more” [31].

Sustainability 2020, 12, 1342 8 of 21

energySustainability requirements 2020, 12, x FOR were PEER based REVIEW on solar power or other alternative forms of energy. Many were8 alsoof 21 Sustainability 2020, 12, x FOR PEER REVIEW 8 of 21 built on wheeled trailer bases to make them portable. Tiny houses are symbols of a simpler lifestyle Nowadays, architects are developing projects integrating prefabrication and ecological concepts. whereNowadays, “less is more” architects [31]. are developing projects integrating prefabrication and ecological concepts. For example, Werner Sobek designed the R128 single-family house in 1998–2000 (see Figure 8). The For example,Nowadays, Werner architects Sobek are design developinged the projectsR128 single-family integrating hous prefabricatione in 1998–2000 and ecological(see Figure concepts. 8). The exposed bolted steel frame was prefabricated offsite, and the triple glazing panel was modular. The Forexposed example, bolted Werner steel frame Sobek was designed prefabricated the R128 offsit single-familye, and the housetriple glazing in 1998–2000 panel (seewas Figuremodular.8). TheThe bathrooms are comprised of pre-fabricated modules inserted into the building [13]. The assembly exposedbathrooms bolted are comprised steel frame of was pre-fabricated prefabricated modules offsite, andinserted the triple into glazingthe building panel [13]. was The modular. assembly The employing offsite pre-fabrication and modular systems can be dismantled, allowing its materials to bathroomsemploying areoffsite comprised pre-fabrication of pre-fabricated and modular modules systems inserted can be intodismantled, the building allowing [13]. its The materials assembly to be either reused or recycled [32]. Another example is R50—cohousing build in Berlin by the Heide employingbe either reused offsite or pre-fabrication recycled [32]. and Another modular exampl systemse is R50—cohousing can be dismantled, build allowing in Berlin its materials by the Heide to be and Von Beckerath office from 2010–2013 (see Figure 9). The project includes 19 individual eitherand Von reused Beckerath or recycled office [32 ].from Another 2010–2013 example (see is R50—cohousingFigure 9). The buildproject in Berlinincludes by the19 Heideindividual and apartments, one studio and shared spaces. The reinforced concrete skeleton is based on the sizes of Vonapartments, Beckerath one offi studioce from and 2010–2013 shared spaces. (see Figure The9 ).reinfo Therced project concrete includes skeleton 19 individual is based apartments, on the sizes one of apartments and the suspended balconies in steel construction connecting them on each floor. The studioapartments and shared and the spaces. suspended The reinforced balconies concrete in steel skeleton construction is based connecting on the sizes them of apartmentson each floor. and The the modular timber facade with opening glazed door elements is independently combined with the suspendedmodular timber balconies facade in steelwith construction opening glazed connecting door elements them on eachis independently floor. The modular combined timber with facade the reduced and partly exposed infrastructure. The internal surfaces are unfinished, and the open design withreduced opening and partly glazed exposed door elements infrastructure. is independently The intern combinedal surfaces with are unfinished, the reduced and and the partly open exposed design allows for individual layouts and a standard grid for fixtures. This design enables resident infrastructure.allows for individual The internal layouts surfaces and are a unfinished,standard grid and thefor openfixtures. design This allows design for individualenables resident layouts participation in interior design [33]. andparticipation a standard in gridinterior for fixtures.design [33]. This design enables resident participation in interior design [33].

Figure 8. Werner Sobek, R128, 1998–2000, Stuttgart, Germany [34]. Figure 8. Werner Sobek, R128, 1998–2000, Stuttgart, Germany [[34].34].

Figure 9. HeideHeide and and Von Von Beckerath, R50 cohousing,cohousing, 2010–2013, Berlin, Germany [[33].33]. Figure 9. Heide and Von Beckerath, R50 cohousing, 2010–2013, Berlin, Germany [33]. Technology improves the design and manufacturingmanufacturing processes through advances in robotics, Technology improves the design and manufacturing processes through advances in robotics, lightweight materials and digitaldigital buildingbuilding information.information . The The risks risks faced faced by earlier modular and lightweight materials and digital building information . The risks faced by earlier modular and prefabrication buildersbuilders are are becoming becoming more more manageable. manageable. Technology Technology has driven has many driven new many companies, new prefabrication builders are becoming more manageable. Technology has driven many new oftencompanies, through often the through use of precision the use modelingof precision and modeling roboticmanufacturing, and robotic manufacturing, to lower costs to and lower improve costs companies, often through the use of precision modeling and robotic manufacturing, to lower costs eandfficiency improve [35 ].efficiency The idea [35]. to use The analogous idea to use examples analogous as examples references as to references obtain inspiration to obtain about inspiration some and improve efficiency [35]. The idea to use analogous examples as references to obtain inspiration problemsabout some in problems the present in isthe not present new. is Throughout not new. Th history,roughout architects history, have archit searchedects have for searched techniques for about some problems in the present is not new. Throughout history, architects have searched for totechniques increase theto increase quality ofthe both quality design of andboth production design and and production used modular and used housing modular to introduce housing and to techniques to increase the quality of both design and production and used modular housing to introduce and improve sustainability and quality control [9]. Each example offers insight into how introduce and improve sustainability and quality control [9]. Each example offers insight into how prefabrication and recyclability should or should not be harnessed to deliver architecture. prefabrication and recyclability should or should not be harnessed to deliver architecture.

Sustainability 2020, 12, 1342 9 of 21 improve sustainability and quality control [9]. Each example offers insight into how prefabrication and recyclability should or should not be harnessed to deliver architecture.

2.3. Discussion Prefabrication is evolutionary, not revolutionary. The solutions to problems are discovered through practice and failure, which leads to an understanding of what works or not. Prefabrication can be a tool by which architecture can impact the built environment, most significantly the housing. The offsite manufacturing processes can offer greater accuracy, shorter construction times, safer working conditions, better value, promote recycling and reduce waste. Although prefabrication can reduce waste materials, it gives no clear indication about the environmental impact of materials used in construction. Prefabrication seems to be a viable solution for buildings to be easily disassembled and reused as industrial supplies [9]. According to Smith [9], the prefabricated projects during history failed for many reasons: Firstly, the sheer cost of updating technologies, replacing components and the dependency on big infrastructures for intervention; secondly, a lower quality and durability of houses in comparison to commercial construction; and finally, the aesthetic impositions and specific ideas, styles and materials that are too complicated to adapt and change according to individual living patterns, since aesthetic preferences change over time. Equally important would be the fact that it is the lack of integrated process in the early stage of design in a building venture that is responsible for many of these failures. The implementation of prefabrication during the earliest stages of the design process encourages all construction collaborators to adapt an affordable, appropriate technology for the built environment. A number of prefabricated architectural experiments throughout the history until today cover basic needs, but do not satisfy the needs for adaptation on demand which are generated more and more by a fast-evolving society [24]. A traditional family model strongly influences housing currently under construction, and the number of households meeting these criteria is decreasing steadily. Moreover, the current housing market does not expect a growing need for communal, hybrid and transferable activities. Our lifestyles require a more integrated relationship between living and working, individual and common, and urban and nature. Building technologies were improved, they implemented concepts of modularization, prefabrication and recyclability, but were still mostly focused on the assembled process of the construction. The structures were assembled, covered and glued by other materials making them demountable and challenging to reuse and unsuitable for disassembling at the end of life. New building concepts should be created in the future, which can be redesigned, upgraded, or disassembled without generating waste. High-rise buildings should integrate mixed uses, including offices, houses, shops and common spaces. Repetition and standardization are the inherent qualities of the mass-production of a consumer-oriented society. However, parts can be changeable or interchangeable depending on individual needs and preferences, and could also be economically feasible [24]. The majority of the buildings are still constructed using concrete, generating a significant CO2 emission and making recycling rather expensive. Concrete is a part of architecture culture and will stay one for years to come, therefore buildings should be designed to address this situation and integrate this material in the construction in a recyclable way. However, nowadays, cities require more sustainable, smart, recycable and green buildings concepts all together. The projects mentioned in Section2 are mostly unitary residential projects. The idea of a temporary building introduced in Futurism should be taken into consideration and translated to the present. The temporary building concept can be achieved using bolted structures as applied for instance in the project of Fuller’s Dymaxion house, the Prepackaged House of Gropius and Wachsmann, Prouvé’s Pavilions and Sorbek’s R128 house. They can be assembled and disassembled easily, although they are only implemented on a small scale. Their concepts can be used to design high-rise buildings nowadays. From the projects of Le Corbusier, Wright and Mies van der Rohe, the rationalization translated into modularity can be highlighted, even if the prefabrication methods required a lot of manual work Sustainability 2020, 12, 1342 10 of 21 onsite. These ideas must be brought to reality, but the prefabrication process during the construction must be improved without generating additional costs and manual labor. Furthermore, the high-tech movement and the metabolism manifesto serve as an inspiration to the large, open and exposed infrastructures allowing different layouts and uses besides plugged-in and -out housing capsules. The plug-in concept can be improved by combining ideas of the Mobile Homes and the Tiny House and as well as the idea of one housing unit which can be transported and installed in a different infrastructure. The challenge of today would be updating these strategies while integrating the ecological strategies used by Otto and SITE in combining nature and the built environment and adding to the reduced use of materials and waste production. Infrastructure and existing buildings should be seen as a valuable cultural, social and architectural resource for shaping our future. The conversion of waste into valuable materials is one example of a positive attitude that needs to be adopted towards the existing stock. The international environmental movement’s slogan “Reduce/Reuse/Recycle” incorporates the waste hierarchy. “Reduce” is aimed primarily at minimizing and avoiding waste. “Reuse” is a direct approach to waste management. “Recycle” comes third on the list as a way of processing material. The less the original waste product needs to be altered, the better is the process. The “3 Rs”, Reduce/Reuse/Recycle, have been applied to architecture to create a hierarchy for strategies of change: the fewer interventions and the less energy expended, the more effective the process [8]. Recycling should be considered another ecological requirement that remains unfulfilled in the actual residential model. The sustainability of the built environment is often limited to the building’s lifecycle, neglecting the grey energy and CO2 emissions produced during the construction and demolition of these buildings. A switch in the architectural culture is necessary, which must take into consideration a broader comprehension of the multiple structural cycles, as well as the evolution of uses and users to create genuinely great solutions to the problems of the present day in a culture of collaboration [9].

3. Proposed Architectural Typologies With the matters discussed above, it is necessary to design buildings to increase their suitability for recycling and future use. Thus, new designs should be capable of addressing ecological challenges and social changes. People’s habits, as well as commodities, are changing at every social level, which eventually impacts the way of living [24]. Architecture should serve the public’s needs, characterized as common and free spaces for the public in the cities, improving the quality of life and the buildings with the implementation of highly developed technology. It is the social questions about the use of the ground and the sum of human needs that constitute the functions that determine the form of a building. The first aspect can be reached by allowing the smallest footprint possible in order to give the population free access to the common ground. Regarding the second aspect, the shared space should be designed as an extension of the house, integrating people with different habits, and providing different activities. It would give residents the possibility to live, work and rest within the same space [21]. The adaptation of the building layout should be considered at the beginning of the design phase [36]. Adaptability relates to the technical performance of parts of the building. In this respect, adaptability is seen as a physical change with the purpose to increase the flexibility-in-use [37]. A large number of modular systems are designed to be manipulated, added, and maintained during their lifecycle, aiming for a building that can be reconfigured, relocated or disassembled for reuse [9]. Taking into the account the different needs of the current society, different conceptual typologies, which implement in the early design stage the possibility of the construction to be adaptable, demountable and recyclable in accordance with the needs of the future society, were developed in this research. The design of buildings is not only a professional practice but also a form of inquiry and research [38]. The different ideas, forms, uses and techniques related to prefabrication and recyclability of historical architectural buildings presented in Section2 served as a starting point for the design principles of the building prototypes developed and discussed at the core of the ECON4SD project. The following sub-sections Sustainability 2020, 12, 1342 11 of 21 present the design principles that guided the development of this research and the details of each developed prototype.

3.1. The Principles The construction of high-rise residential blocks is intended to increase the density of the population in the city center, at the same time creating open public and sharing spaces. The profile of the occupants in these buildings is the new generation of young workers living alone, or young couples with possibly one child. Therefore, the house units and apartments were designed to adapt to all kinds of use and to be affordable for all social classes, giving the population equal power for choosing how they want to live. The buildings can be designed to provide flexibility, allowing different uses during their foreseen lifespan and the possibility to demount and remount the components in another place. This research aimed to produce alternative generic models, which would allow functional flexibility through time. Therefore three different recyclable architectural conceptual typologies were developed to have a more significant advantage of each system realistically and feasibly. They were named Slab, Tower and Demountable according to their stronger characteristics. The main principles for these building designs are: the possibility to be disassembled and recycled at the end of their life; the use of large-scale structures for flexible usage in a variety of types of modular and prefabricated construction methods; a highly effective space with a minimal footprint; and the integration individual types of accommodation with communal activities. For every different architectural typology, a structural, functional, spatial, constructive and aesthetic coherence was developed. The first step in designing recyclable buildings is to consider their life cycle. The construction elements at the end of their service life should be transformed into resources for other buildings, closing loops in industrial ecosystems and minimizing waste. The structures were conceived to be disassembled and reconfigured throughout the lifecycle of the building. The exposed structure can facilitate the process of disassembly, consequently reducing the waste remaining at the end of the life cycle of the building. Therefore, the entire building structure or some parts, such as beams, slabs and pillars, among others, can be recycled, either to relocate the building, reuse components to build a new structure or to recycle the materials to create new ones. Furthermore, the structure and internal layout can be reconfigured for different functions, e.g., the same area transforming into a house or an office, depending on the necessity of the society. The rationalization of the massive structure, both internal and external, was achieved by using grid systems, prefabricated components and modular units, which optimize the disassembly and the reconfiguration. Furthermore, the mega and prefabricated structures allow the most extended spans that provide more flexible uses and different layouts according to the user’s needs. In addition, modular structures or modular buildings increase the possibilities for building expansion. In order to have a highly functional space with a minimal footprint, reducing the area which provides access to the building should be put into consideration. A central core is one of the solutions adopted to reduce the structure on the ground floor, which can include the elevators, stairs and technical shafts. The smallest footprint and the most opened space generate public zones that can be explored such as shops, gathering spaces, and urban gardens. The buildings offer places where the residents can have moments to be on their own and moments to meet others. The housing units were designed to reduce the space necessary to live, including cooking, eating, sleeping, taking care of hygiene and working, already proclaimed by Le Corbusier in “Vers Une Architecture.” The dwelling can adapt according to the needs of contemporary families, while the buildings can receive more than one type of residential layout. As an example, the dwellings can reduce and increase their size for one resident, a couple, and a couple with kids. Finally, all the prototypes have public space and communal areas to improve residents’ life, with more facilities at the same location, which satisfy the group activity needs. These spaces are the extension of the housing and users’ life. The shared zones were variously placed on the ground floor, Sustainability 2020, 12, 1342 12 of 21

Sustainabilityon the rooftop 2020, and12, x FOR were PEER also REVIEW given by the circulation on the different floor levels. The activities12 can of 21 be selected initially and then adapted through time according to the needs of the residents or the city itself,neighborhoods—for however they example,can also be swimming combined pools, with saunas, other sportsmodules facilities, to provide urban more gardens, than kindergartens, one type of activity.libraries and markets. Some buildings function as an independent module in and of itself, however theyTo can conclude, also be combined the prototypes with other have modulesthe capacities to provide to be morein a continuous than one type evolution of activity. from one state to another.To conclude, They are the complete prototypes but havealways the in capacities transition to to be adapt in a continuousto the users' evolution needs. The from design one stateand executionto another. methodology They are complete focused but on alwaysthe efficiency in transition of use and to adapt implementation, to the users’ attempting needs. The to design leverage and existingexecution methods methodology of residentia focused onl prefabrication. the efficiency of The use andresearch implementation, by design attempting methodology to leverage was implementedexisting methods to reach of residential the final prefabrication.shape of the three The prototypes. research by designDrawing, methodology plans and was3D models implemented were tested,to reach analyzed the final and shape the offeasibility the three and prototypes. construction Drawing, was demonstrated. plans and 3D modelsSection were3.2 describes tested, analyzedin more detailand the and feasibility individually and each construction one of the was final demonstrated. designs for three Section prototypes. 3.2 describes in more detail and individually each one of the final designs for three prototypes. 3.2. Prototype 1: Slab 3.2. Prototype 1: Slab The main objective of the Slab prototype is to increase density by providing more housing with sharedThe spaces. main objectiveThe building of the is Slab designed prototype to allow is to increasedifferent density arrangements by providing of the more dwellers housing giving with flexibilityshared spaces. to house The units building to grow is hosting designed different to allow families’ different numbers arrangements and residents. of the Furthermore, dwellers giving to reachflexibility these to concepts, house units the building to grow hostinghas a reduced different footprint families’ providing numbers more andresidents. space for public Furthermore, use, and to thereach rooftop these is concepts, a common the area. building has a reduced footprint providing more space for public use, and the rooftopThe prototype is a common is an 11-story area. building consisting of a primary reinforced concrete structure and connectedThe prototype wooden housing is an 11-story units, buildingas shown consisting in Figure of10. a The primary shelf-structure reinforced provides concrete structurea stable slab and withconnected a structure wooden extending housing units,over two as shown floors in for Figure standardized, 10. The shelf-structure prefabricated provides and portable a stable slabhousing with modules.a structure These extending modules over offer two floorsa living for space standardized, designed prefabricated for either a andsingle portable person housing or a couple. modules. A housingThese modules unit plan offer was a living developed space designed from one for eitherto four a singleconfigurations, person or acapable couple. Aof housingexpanding unit and plan shrinkingwas developed as needed, from as one presented to four configurations, in Figure 11. Fo capabler each ofone expanding of the housing and shrinking units, there as needed, is also asa commonpresented area, in Figure which 11 adds. For up each to onea significantly of the housing below-average units, there floor is also surface a common per inhabitant area, which as addsper standards.up to a significantly The modules below-average are positioned floor in the surface main per facade inhabitant of the building, as per standards. and they Thecan be modules added areor removedpositioned by in a thecrane main at any facade time. of theThey building, can be andtransported they can by be any added standard or removed truck, by and a crane can be at anyquickly time. assembledThey can be and transported removed in by rails. any standard truck, and can be quickly assembled and removed in rails.

FigureFigure 10. 10. PrototypePrototype 1—Slab: 1—Slab: diagram. diagram.

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Sustainability 2020, 12, 1342 13 of 21 Sustainability 2020, 12, x FOR PEER REVIEW 13 of 21

Figure 11. Prototype 1—Slab: 1st level floor plan.

One-side building orientation allows the dwellings to receive natural light on two facades. The modules are positioned in the main facade of the building. The stairs are integrated into the opposite facade, as seen in Figure 12, reducing the vertical core and creating an open corridor that becomes a large sharing balcony in front of the doors and compensates for a reduced size of the housing units. The vertical core is positionedFigureFigure on one 11.11. side PrototypePrototype of the 1—Slab:1—Slab: building 1st1st to level level access floor floor the plan. plan. elevat or and shafts, integrating some facilities such as small laundries. One-sideThe optimization building of orientation the housing allows surface the area dwellings is associated to receive with natural a range light of ononcommunal twotwo facades.facades. activities The moduleson the top are floor. positioned These activities in the main are facade theme-orient of the building.bued,ilding. from Thea recreation stairs are area integrated with a intoswimming the opposite pool, facade,through as a seenshared in analog Figure lounge,1212,, reducingredu allcing the the way vertical to a collaborative core and creating workspace. an open This corridor space will that be becomes designed a largeaccording sharing to the balcony local in needs. front The of the ground doors floor and offerscomp compensates ensatesan envelope for a reducedthat can be size occupied of the housing according units. units. to Thethe location vertical coreof the is positionedbuilding: in on urban one side situations of the bu buildingmainlyilding by to accessshops, the in suburban elevat elevatoror and cases shafts, more integrating by offices someor workspaces. facilities such as small laundries. The optimization of the housing surface area is associated with a range of communal activities on the top floor. These activities are theme-oriented, from a recreation area with a swimming pool, through a shared analog lounge, all the way to a collaborative workspace. This space will be designed according to the local needs. The ground floor offers an envelope that can be occupied according to the location of the building: in urban situations mainly by shops, in suburban cases more by offices or workspaces.

(a) (b)

FigureFigure 12.12. Prototype 1—Slab 3D3D model:model: (a) frontal facade;facade; ((b)) backback facade.facade.

The optimization of the housing surface area is associated with a range of communal activities on the top floor. These activities are theme-oriented, from a recreation area with a swimming pool, through a shared analog lounge, all the way to a collaborative workspace. This space will be designed according to the local(a) needs. The ground floor offers an envelope that can(b) be occupied according to the location of theFigure building: 12. Prototype in urban 1—Slab situations 3D model: mainly (a) frontal by shops, facade; in suburban(b) back facade. cases more by offices or workspaces. The building itself is a module that can be extended depending on the terrain and demand. Figure 13 is a simulation of this extension, integrating more than one module. Its structure allows the development of land that is difficult to build on. In addition, the Slab building represents an infrastructure that can be placed in many neighborhoods or cities, and the housing units can move with their owners by truck and plug-in into another Slab infrastructure. We can say that the typologies are a mix of ideas such as rationalization, modularity, prefabrication, plug-in and recyclability to reach Figure 13. Prototype 1—Slab: 3D simulation extension. the circularity in the construction. The concept of the housing unit that can be added in or out of the structure responds to the demands on a circular building. Since the housing units are made of timber, the maintenance and replacement through time are simplified. As this material is not exclusive to one industry, if a change occurs in the local economy, similar modules still can be fabricated by different companies. Figure 13. Prototype 1—Slab: 3D simulation extension.

Sustainability 2020, 12, x FOR PEER REVIEW 13 of 21

Figure 11. Prototype 1—Slab: 1st level floor plan.

One-side building orientation allows the dwellings to receive natural light on two facades. The modules are positioned in the main facade of the building. The stairs are integrated into the opposite facade, as seen in Figure 12, reducing the vertical core and creating an open corridor that becomes a large sharing balcony in front of the doors and compensates for a reduced size of the housing units. The vertical core is positioned on one side of the building to access the elevator and shafts, integrating some facilities such as small laundries. The optimization of the housing surface area is associated with a range of communal activities on the top floor. These activities are theme-oriented, from a recreation area with a swimming pool, through a shared analog lounge, all the way to a collaborative workspace. This space will be designed according to the local needs. The ground floor offers an envelope that can be occupied according to the location of the building: in urban situations mainly by shops, in suburban cases more by offices or workspaces.

(a) (b) Sustainability 2020, 12, 1342 14 of 21 Figure 12. Prototype 1—Slab 3D model: (a) frontal facade; (b) back facade.

Figure 13. Prototype 1—Slab: 3D simulation extension. 3.3. Prototype 2: Tower The second prototype is a mixture of uses with different possibilities of floor organization, which may include different dimensions of apartments for different social classes combined with community facilities and sharing spaces. The project’s ambition is towards an architecture with a minimal structure that implies open space and recyclability. This typology refers to a 25-story tower, with a wooden structure wrapped around a reinforced concrete core. The building structure remains visible and will be fully prefabricated and recyclable, as shown in Figures 14 and 15. The form strives to reduce the footprint to a minimum, aiming to support a variety of shared activities, e.g., urban farming, which brings the community together, added to the reduction of the unnatural ground. The building is designed on a grid of 3.2 3.2 m, as shown in × Figure 15, to facilitate the process of prefabrication by rationalization of elements. The variations of slab sizes enables different uses and diverse housing unit layouts. The two lower and upper floors accommodate other community facilities such as a pre-school, living room, kitchen and sports venues. The central floors, with a large surface area, are dedicated to collaborative workspaces, while the intermediate levels are reserved for residence. The internal arrangement of walls, bathrooms and kitchens are adaptable since the infrastructure services are integrated into the ceiling. Through the varying categories, these housing units allow the integration of a diversified population. Therefore, the building complex seeks a mixture: between living and working, various social classes, private and common activities. A diagram with the different inside uses of the Tower is presented in Figure 14. Sustainability 2020, 12, x FOR PEER REVIEW 15 of 21

Sustainability 2020, 12, x FOR PEER REVIEW 15 of 21 Sustainability 2020, 12, 1342 15 of 21

(a)(a) (b) (b)

FigureFigureFigure 14. 14.14. PrototypePrototype Prototype 2—Tower: 2—Tower: (a ( a)( )aprototype) prototype prototype 1: 1: 3D1: 3D 3Dsimulation; simulation; simulation; (b) ( bprototype()b prototype) prototype 1: section 1: 1: section section showing showing showing didifferentdifferentfferent uses. uses. uses.

(a) (b) (a) (b) Figure 15. Prototype 2: (a) Tower: grid of 3.2 × 3.2 meters, 10th level; (b) Tower: 3D model. Figure 15. PrototypePrototype 2: ( (aa)) Tower: Tower: grid grid of of 3.2 3.2 × 3.23.2 meters, m, 10th 10 level;th level; (b) ( Tower:b) Tower: 3D 3D model. model. ×

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3.4. Prototype 3: Demountable 3.4.3.4. Prototype Prototype 3: Demountable 3: Demountable The idea of a complete disassemblable and recyclable building is implemented in the third TheThe idea idea of ofa complete a complete disassemblable disassemblable and and recyclable recyclable building building is isimplemented implemented in inthe the third third prototype named Demountable. The building is flexible in many situations, adjusting the interior prototypeprototype named named Demountable. Demountable. The The building building is flexible is flexible in inmany many situations, situations, adjusting adjusting the the interior interior layout, prolonging, shifting and reconfiguring the exterior format, being disassembled and layout,layout, prolonging, prolonging, shiftingshifting andand reconfiguring reconfiguring the exteriorthe exterior format, format, being disassembled being disassembled and reassembled and reassembled in another place to adapt to future needs. Since the structure or its parts can no longer reassembledin another placein another to adapt place to futureto adapt needs. to future Since need the structures. Since the or itsstructure parts can or noits longerparts can be reused,no longer they be reused, they must be recycled into new materials. As a result, we close the loop, and the bemust reused, be recycledthey must into be new recycled materials. into As new a result, mate werials. close As the a loop,result, and we the close construction the loop, life and becomes the construction life becomes circular. The building starts from a prefabricated basic standard block that constructioncircular. The life building becomes starts circular. from The a prefabricated building starts basic from standard a prefabricated block that basic can standard grow in all block directions, that can grow in all directions, adding more components or whole blocks if needed to facilitate the canadding grow morein all components directions, oradding whole more blocks componen if neededts to or facilitate whole the blocks disassembly if needed process, to facilitate as illustrated the disassembly process, as illustrated in Figure 16. The structure is adaptable for steel or timber disassemblyin Figure 16 process,. The structure as illustrated is adaptable in Figure for steel 16 or. The timber structure components. is adaptable The internal for steel span lengthor timber of the components. The internal span length of the generic model allows different layouts for housing units, components.generic model The allowsinternal di spanfferent length layouts of the for generi housingc model units, allows offices, different cars, gyms layouts and saunas,for housing for example. units, offices, cars, gyms and saunas, for example. The replication and combination of these generic models offices,The replication cars, gyms and and combination saunas, for example. of these genericThe replication models o andffer combination the possibility of to these design generic buildings models with offer the possibility to design buildings with different uses, such as parking, public facilities, shops, offerdiff theerent possibility uses, such to as design parking, buildings public facilities,with differen shops,t uses, offices such and ashousings, parking, public and sometimes facilities,a shops, mixture offices and housings, and sometimes a mixture of them. officesof them. and housings, and sometimes a mixture of them.

(a) (a) (b)(b) Figure 16. 16. PrototypePrototype 3—Demountable: 3—Demountable: (a) architectural (a) architectural concept concept for the for standard the standard block; block;(b) the blocks’ (b) the Figure 16. Prototype 3—Demountable: (a) architectural concept for the standard block; (b) the blocks’ expansion.blocks’ expansion. expansion. This study presents two scenarios for this typology. The first configuration is a car parking ThisThis study study presents presents two two scenarios scenarios for for this this typology. typology. The The first first configuration configuration is isa cara car parking parking building with public space on the rooftop with a swimming pool, sauna, gym and sports courts, as buildingbuilding with with public public space space on on the the rooftop rooftop with with a swimminga swimming pool, pool, sauna, sauna, gym gym and and sports sports courts, courts, as as shown in Figures 17 and 18. Vertical access is added as an external structure to keep the main structure shownshown in inFigures Figures 17 17 and and 18. 18. Vertical Vertical access access is isadded added as asan an external external structure structure to tokeep keep the the main main as free as possible. Through time, the constructed environment can be adapted to accommodate future structurestructure as asfree free as aspossible. possible. Through Through time, time, the the constructed constructed environment environment can can be be adapted adapted to to demands while keeping the same structure. Some parking floors can be transformed into offices and accommodateaccommodate future future demands demands whil while ekeeping keeping the the same same structure. structure. Some Some parking parking floors floors can can be be others into housing, adding interior walls. Moreover, the ground floor can become shops, leisure transformedtransformed into into offices offices and and others others into into housing, housing, adding adding interior interior walls. walls. Moreover, Moreover, the the ground ground floor floor spaces or a covered square that bring citizens together. cancan become become shops, shops, leisure leisure spaces spaces or ora covereda covered square square that that bring bring citizens citizens together. together.

(a) (a) (b)(b) Figure 17. Prototype 3—Demountable: (a) the first configuration: mix using public facilities and FigureFigure 17. 17. PrototypePrototype 3—Demountable: 3—Demountable: (a) (thea) the first first configuration: configuration: mix mix using using public public facilities facilities and and parking, housings and offices; (b) the building extension. parking,parking, housings housings and and offices; offices; (b) ( bthe) the building building extension. extension.

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(a)(a) (b)(b)

FigureFigureFigure 18. 18. 18. PrototypePrototype Prototype 3—Demountable: 3—Demountable: 3—Demountable: (a ()a (3Da)) 3D 3D Simulation; Simulation; Simulation; (b ( )b( b3D)) 3D 3D model. model. model.

TheTheThe second secondsecond configuration configurationconfiguration is isisshown shownshown as as asa a continuationa continuation continuation of of ofthe the the building building building life-cycle. life-cycle. life-cycle. The TheThe structure structurestructure needsneedsneeds to to tobe be bedisassembled disassembled disassembled and and and relocated. relocated. relocated. The The The buildin building building can g can maintain maintain thethe the samesame same formform form asas before asbefore before or or can orcan can be beadjusted beadjusted adjusted to to other toother other needs needs needs as aas housing asa housinga housing complex complex complex or an or o ffiorance an office building office building building with di withff erentwith different heightsdifferent heights and heights numbers and and numbersofnumbers blocks, of asofblocks, shownblocks, as inasshown Figureshown in 19inFigure. Figure All remaining19. 19. All All remaining remaining parts from parts parts the from oldfrom the structure the old old structure structure should should be should reused be bereused in reused other inconstruction inother other construction construction or recycled, or orrecy recy producingcled,cled, producing producing new materials. new new materials. materials.

(a)(a) (b)(b)

FigureFigureFigure 19. 19. 19. PrototypePrototype Prototype 3—Demountable: 3—Demountable:3—Demountable: (a) ( (ahousinga)) housinghousing complex/office complexcomplex/office/office building; building; building; (b ( )b( btheir)) their their expansion. expansion. expansion. 3.5. Discussion and Benefits of the New Recyclable Prototypes 3.5.3.5. Discussion Discussion and and Benefits Benefits of theof the New New Recyclable Recyclable Prototypes Prototypes The aim of the prototypes is to examine the relevant issues of recyclable strategies and prefabricated TheThe aim aim of ofthe the prototypes prototypes is isto toexamine examine the the re levantrelevant issues issues of ofrecyclable recyclable strategies strategies and and and modular systems in construction so as to increase flexibility, adaptability and disassembly in the prefabricatedprefabricated and and modular modular systems systems in inconstruction construction so soas asto toincrease increase flexibility, flexibility, adaptability adaptability and and architectural design. The results presented in this paper are innovative tools and approaches which are disassemblydisassembly in inthe the architectural architectural des design.ign. The The results results presented presented in inthis this paper paper are are innovative innovative tools tools and and to be implemented at the beginning of the design process and that can be adapted to other buildings. approachesapproaches which which are are to tobe beimplemented implemented at atthe the beginning beginning of ofthe the design design process process and and that that can can be be The architectural typologies introduced in this paper bring direct solutions, combinations or adaptedadapted to toother other buildings. buildings. improvements of designs and prefabricated and modular systems from constructed buildings presented TheThe architectural architectural typologies typologies introduced introduced in inthis this paper paper bring bring direct direct solutions, solutions, combinations combinations or or in Section2. In order to validate the viability and to highlight the improvement of the three prototypes, improvementsimprovements of ofdesigns designs and and pr efabricatedprefabricated and and modular modular system systems froms from constructed constructed buildings buildings a comparison is made between them. The main difference is the fact that the three prototypes are presentedpresented in inSection Section 2. In2. Inorder order to tovalidate validate the the vi abilityviability and and to tohighlight highlight the the improvement improvement of ofthe the three three high-rise buildings designed to be adaptable through time and disassembled at the end of their life prototypes,prototypes, a comparisona comparison is ismade made between between them. them. Th The maine main difference difference is isthe the fact fact that that the the three three through prefabrication and modulation, at the same time providing a large amount of housing units prototypesprototypes are are high-rise high-rise buildings buildings designed designed to tobe beadaptable adaptable through through time time and and disassembled disassembled at atthe the combined with more shared and public areas. The Slab buildings are focused on the housing expansion endend of oftheir their life life through through prefabrication prefabrication and and modula modulation,tion, at atthe the same same time time providing providing a largea large amount amount and plug-in concepts, accommodating 48 portable housing units; the floors of the Tower prototype of ofhousing housing units units combined combined with with more more shared shared and and pub public licareas. areas. The The Slab Slab buildings buildings are are focused focused on on the the can be divided to configure 140 apartments emphasizing the internal flexibility of the structure; and housinghousing expansion expansion and and plug-in plug-in concepts, concepts, accommodating accommodating 48 48portable portable housing housing units; units; the the floors floors of ofthe the the prototype Demountable is designed to comprise 58 single housing units per floor (three single TowerTower prototype prototype can can be bedivided divided to toconfigure configure 140 140 ap apartmentsartments emphasizing emphasizing the the internal internal flexibility flexibility of of housing units in one standard block) focusing on the complete disassembly. Even though the other thethe structure; structure; and and the the prototype prototype Demountable Demountable is deis designedsigned to tocomprise comprise 58 58single single housing housing units units per per buildings integrated the prefabrication and modular system, they focused on the assembly process floorfloor (three (three single single housing housing units units in inone one standard standard block) block) focusing focusing on on the the complete complete disassembly. disassembly. Even Even and not on the disassembly, making it more difficult to reuse or recycle, which generates more waste. thoughthough the the other other buildings buildings integrated integrated the the prefabri prefabricationcation and and modular modular system, system, they they focused focused on on the the Until the 1960s, the prefabrication and modular systems were widely implemented in the individual assemblyassembly process process and and not not on on the the disassembly, disassembly, making making it moreit more difficult difficult to toreuse reuse or orrecycle, recycle, which which homes. The three prototypes took advantage of this rationalization on a small scale and translated it generatesgenerates more more waste. waste. Until Until the the 1960s, 1960s, the the prefabrication prefabrication and and modular modular systems systems were were widely widely to a large scale, using grids to design high-rise buildings, demonstrating that the implementation of implementedimplemented in inthe the individual individual homes. homes. The The three three prot prototypesotypes took took advantage advantage of ofthis this rationalization rationalization on on prefabrication and modularity in large buildings facilitates the process of construction disassembly and a smalla small scale scale and and translated translated it to it toa large a large scale, scale, using using grids grids to todesign design high-rise high-rise buildings, buildings, demonstrating demonstrating thatthat the the implementation implementation of ofprefabrication prefabrication and and modularity modularity in inlarge large buildings buildings facilitates facilitates the the process process of of

Sustainability 2020, 12, 1342 18 of 21 the adaptation of the structure for different uses. The concrete blocks of “Habitat 67” were combined to build a building, nevertheless they were too heavy to be easily installed or relocated. The “Nakagin Tower“ also has modules, capsules attached to a core, but the layout was concise for the essential needs without the possibility to combine them to create big units. From “Habitat 67” and “Nakagin Tower” the concept of housing modules and plug-in systems mixing with the portable houses—Tiny House and Mobile homes—were brought to the Slab building, improving the possibility to extend the residence and to be connected in more than one infrastructure, since it employs timber, a lighter structure than concrete. The Archigram studies were focused on creating a discussion and theory in architecture with images and propaganda. Added to the opening of the debate on recyclability, the Slab, Tower and Demountable prototypes are realistic and provide more details and concerns about the feasibility of the construction. The ecological and recyclable examples inspired the integration of nature, the lightweight and exposed structures with open slabs in the construction showing that it is possible to easily modify internal layouts, extend and change the built environments throughout their useful life. However, they do not guarantee the environment’s effects of the building at the end of life. By contrast, the three Recyclable Architecture typologies are designed from the beginning to reintegrate the materials into the life cycle in other buildings. These typologies can be built in many neighborhoods or in many cities where new construction is required to provide residential, commercial, shared and public spaces while enabling the adaptation to social and future needs, reducing the use of resources and construction waste. The projects of the buildings can be adapted to the regulations of each region while keeping the same typology. To illustrate, the prototypes’ height can be changed, adding or reducing some levels. More staircases can be connected to the Demountable typology. The dimensions of the Tower building can be expanded in proportion. The number of modules of the Demountable and the Slab building repetition can be related to the dimensions of the terrain. Moreover, the Slab, Tower and Demountable prototypes and concepts intend to serve as a guideline for other building projects. Therefore the prefabrication and modularity can be used in different manners to increase the flexibility and disassembly of the building. The design of these three prototypes brings several benefits to the construction field. They are listed below: The design brings more value to the construction and to the life of the residents. As an example • it could be mentioned that this design provides more communal space inside the buildings. In the Tower prototype, the common areas are localized in the upper and lower floors. In the Slab prototype, the rooftop and corridors are the shared spaces. Moreover, the Demountable prototypes have a public access rooftop, and the ground floors of all Prototypes are public spaces. These strategies integrate living, working and leisure in the same building. The open design enables home expansion according to the needs of the resident. In the Slab • building, the modules can be pluged in and out and connected. In the Tower and Demountable buildings, the open slabs without walls can change the layout easily. As a result, the floors can be adapted to different uses, e.g., the slabs can accommodate apartments and later on the interior layout can be changed to become offices. The use of primary resources and waste is reduced by proposing in the earliest stages of • architectural design, for all the three prototypes, the use of recycled materials, and by predicting changes and disassembly that may occur over the useful life of the building or at the end of the first cycle. To complement the above, the transition of structure reconfiguration, additions, and subtractions • through time is facilitated because the structure is separated from the liming. The housing modules are separated from the infrastructure in the Slab typology, and the walls are separated from the bolted structure in the Tower and Demountable. All prototypes serve as material banks for the construction of future buildings, considering that • from the beginning, all the elements of the buildings can be traced and are designed to be separated and reused in other constructions, by adopting raw materials, exposed structures, and systems that can be plugged in and out, which keeps the loop of materials closed. For example, the Sustainability 2020, 12, 1342 19 of 21

Slab housing modules can be used in other building and their wood reused in other structures. Secondly, the structure of the Tower can be demounted and reused since it is build entirely in timber and the walls can be relocated. Finally, the Demountable prototype was designed to be entirely demountable, so beams, walls, slabs and walls can be reused in different constructions. Parallel disassembly is allowed to minimize time onsite, for instance, the removal of modules or • prefabricated slabs where parts can be detached later. Mechanical, electrical and plumbing systems are consolidated into core units to minimize runs • and hence unnecessary entanglement.

To conclude and summarize the advantages of the conceptual typologies, the main idea of a Recyclable Architecture by using the proposed typologies can be reached. The Recyclable Architecture concept is defined as a modular and disassemblable construction that allows functional flexibility through time and reusability and recyclability of materials at the end of life, while integrating public and shared spaces according to the needs of society.

4. Conclusions Architects keep designing in the same manner as before for a permanent building. By contrast, the concepts of Recyclable Architecture at the beginning of the construction project are extremely necessary to address the huge demand for additional buildings required to accommodate the new generations while at the same time reducing the use of natural resources and minimizing the materials wasted during construction. Prefabrication and modularity were important in the history of architecture for understanding these methods of implementing and improving them, simplifying the process of disassembling at the end of the first building’s life cycle. Consequently, the concept of Recyclable Architecture has to be established and widespread. This paper briefly examined prefabricated and recyclable building in architecture and proposed three new typologies. The aim of this research can be reduced to how the building can integrate the concepts of recyclability and disassembly realistically and feasibly. The three buildings prototypes presented in this article differ from other buildings as the concepts of Recyclable Architecture were implemented at the beginning of the design process, foreseeing what would happen after the useful life of the building and proposing solutions for them to be entirely or in parts recycled. Moreover, the typologies are a combination of a recycled building that provides different uses offering more generous spaces as public and communal areas for the inhabitants and society. The prototypes prove that a recyclable architecture with the current technologies is viable and can be built in any location where there is a demand to implement new buildings while reducing waste. In addition, after the life cycle the buildings can be adapted for the new demands or be disassembled to give a space for other typologies using the same materials, thus saving energy from product manufacturing. To summarize, the proposed typologies give the options and freedom for the future society to decide what they want to do with the building. In other words, the architecture of today can be made to serve the needs of the future. To conclude, the study presents limitations: more architecture and structural details and technical issues should have to be considered in order to reach a more advanced generic model, as they can have an impact on the final design. In addition, the lack of quantitative data in the architecture field is an obstacle and should be tackled by researchers. However, the main benefits of implementing these prototypes in the urban fabric are the increased life span and usability, avoiding demolition and reducing waste to zero. In addition, they change the architecture perspective and construction from a permanent to a mutable building, through space and time and from linear to a circular process. As future efforts for this research project, quantitative data on building materials will be collected and analyzed in order to establish metrics for buildings’ modularity, recyclability, and disassembly.

Author Contributions: Conceptualization, M.F.S. and F.H.; Formal analysis, M.F.S. and F.H.; Funding acquisition, D.W.; Investigation, M.F.S.; Methodology, M.F.S. and F.H.; Project administration, D.W.; Resources, M.F.S.; Sustainability 2020, 12, 1342 20 of 21

Writing—original draft, M.F.S.; Writing—review and editing, L.B.J. and D.W. All authors have read and agreed to the published version of the manuscript. Funding: This research is in the framework of the project Eco-construction for Sustainable Developments (ECON4SD), supported by the program “Investissement pour la croissance et l’emploi”—European Regional Development Fund (2014–2020) (Grant agreement: 2017-02-015-15). Acknowledgments: The authors would like to thank the whole team of the ECON4SD project—web-link https://econ4sd.uni.lu/. Conflicts of Interest: The authors declare no conflict of interest.

References

1. United Nations. The World’s Cities in 2018—Data Booklet (ST/ESA/ SER.A/417); United Nations: New York, NY, USA, 2018; p. 34. 2. United Nations. UN World Population Prospects The 2017 Revision; United Nations: New York, NY, USA, 2017; Volume 136. 3. Ellen Macarthur Foundation. Cities in the Circular Economy: An Initial Exploration; Ellen Macarthur Foundation: Cowes, UK, 2017. 4. Kibert, C.J. Deconstruction: The start of a sustainable materials strategy for the built environment. Ind. Environ. 2003, 26, 84–88. 5. Rashid, A.F.A.; Yusoff, S. A review of life cycle assessment method for building industry. Renew. Sustain. Rev. 2015, 45, 244–248. [CrossRef] 6. European Commission Eurostat. Waste statistics. 2014. Available online: https://ec.europa.eu/eurostat/ statisticsexplained/ (accessed on 24 July 2019). 7. Otto, F.; Songel, J.M. Conversation with Frei Otto; Princeton Architectural Press: New York, NY, USA, 2010. 8. Petzet, M.; Heilmeyer, F. Reduce, Reuse, Recycle. In Architecture as Resource; Hatje Cantz: Berlin, Germany, 2012; ISBN 978-3-7757-3425-7. 9. Smith, R. Prefab Architecture: A Guide to Modular Design and Construction; John Wiley & Sons: Hoboken, NJ, USA, 2010; ISBN 9780470275610. 10. Akbarnezhad, A.; Ong, K.C.G.; Chandra, L.R. Economic and environmental assessment of deconstruction strategies using building information modeling. Autom. Constr. 2014, 37, 131–144. [CrossRef] 11. Chen, T.Y.; Burnett, J.; Chau, C.K. Analysis of embodied energy use in the residential building of Hong Kong. Energy 2001, 26, 323–340. [CrossRef] 12. Heinlein, F.; Sobek, W. Recyclable by Werner Sobek; Avedition Gmbh: Stuttgart, Germany, 2019. 13. Guy, B.; Ciarimboli, N. DfD: Design for Disassembly in the Built Environment: A Guide to Closed-Loop Design and Building; Hamer Center for Community Design: State College, PA, USA, 2005. 14. Mule, J.Y. Design for Disassembly Approaches on Product Development. Int. J. Sci. Eng. Res 2012, 3, 996–1000. 15. Hensel, M.U. Introduction to design innovation for the built environment—research by design and the renovation of practice. In Design Innovation for the Built Environment: Research by Design and the Renovation of Practice; Routledge: Abingdon-on-Thames, UK, 2012. 16. Staib, G.; Dörrhöfer, A.; Rosenthal, M. Components and Systems: Modular Construction—Design, Structure, New Technologies; Walter de Gruyter: Berlin, Germany, 2008; ISBN 978-3-0346-1566-2. 17. Lambert, A.J.D.; Gupta, S.M. Disassembly Modeling for Assembly, Maintenance, Reuse and Recycling; CRC Press: Boca Raton, FL, USA, 2004. 18. Hearn, J. The Prefab Museum Education Pack: Post War Prefabs. 2018. Available online: https://www. prefabmuseum.uk/content/history/education-pack-2 (accessed on 29 October 2019). 19. Arif, M.; Egbu, C. Making a case for offsite construction in China. Eng. Constr. Archit. Manag. 2010, 17, 536–548. [CrossRef] 20. Jaillon, L.; Poon, C.S.; Chiang, Y.H. Quantifying the waste reduction potential of using prefabrication in building construction in Hong Kong. Waste Manag. 2009, 29, 309–320. [CrossRef] 21. Kruft, H.-W. A History of Architectural Theory: From Vitruvius to the Present; Princeton Architectural Press: New York, NY, USA, 1994. 22. Berthier, S. Timber in the buildings of Jean Prouvé: An industrial material. Constr. Hist. Soc. 2015, 30, 87–106. Sustainability 2020, 12, 1342 21 of 21

23. Jean Prouvé/Maison démontable 6 6—Adaptation Roger Stirk Harbour + Partners. Available online: × https://issuu.com/patrickseguin/docs/maison-6x6-rshp (accessed on 23 December 2019). 24. Cook, P. Archigram; Princeton Architectural Press: New York, NY, USA, 1999. 25. Tamari, T. Metabolism: Utopian Urbanism and the Japanese Modern Architecture Movement. Theoryculture Soc. 2014, 31, 201–225. [CrossRef] 26. Galeria de Clássicos da Arquitetura: Nakagin Capsule Tower/Kisho Kurokawa—2. Available online: https://www.archdaily.com.br/br/01-36195/classicos-da-arquitetura-nakagin-capsule-tower-kisho- kurokawa/36195_36197 (accessed on 23 December 2019). 27. Rifkin, J. The Third Industrial Revolution: How Lateral Power Is Transforming Energy, the Economy, and the World; St. Martin’s Griffin: New York, NY, USA, 2011. 28. United Nations Framework Convention on Climate Change (UNFCCC). Kyoto Protocol Reference Manual: On accounting of emisions and assigned amount. UNFCCC, 2008. Available online: https://unfccc.int/ resource/docs/publications/08_unfccc_kp_ref_manual.pdf (accessed on 4 December 2019). 29. SITE High-Rise of Homes. Available online: https://www.siteenvirodesign.com/content/high-rise-homes (accessed on 11 November 2019). 30. The Okohaus—Frei Otto’s participative experiment in Berlin. Available online: http://www.the-offbeats.com/ articles/building-together-the-okohaus-frei-otto-collective-improvisation/ (accessed on 19 November 2019). 31. Mok, K. The Modern House Bus: Mobile Tiny House Inspirations; The Countryman Press: New York, NY, USA, 2018. 32. R128. Available online: https://www.wernersobek.de/en/projects/focus-en/design-en/r128/ (accessed on 24 December 2019). 33. Heide & von Beckerath. Available online: https://heidevonbeckerath.com/single/r50-cohousing (accessed on 22 December 2019). 34. Werner Sobek Group R128. Available online: https://www.wernersobek.de/en/projects/focus-en/design-en/ r128/ (accessed on 14 November 2019). 35. Jaffe, E. Available online: https://www.sidewalklabs.com/blog/when-affordable-housing-starts-in-a-factory/ (accessed on 15 November 2019). 36. Kumar Dhar, T.; Maruf Hossain, M.S.; Rubayet Rahaman, K. How does flexible design promote resource efficiency for housing? A study of Khulna, Bangladesh. Smart Sustain. Built Environ. 2013, 2, 140–157. [CrossRef] 37. Gijsbers, R.; Lichtenberg, J.; Erkelens, P. A new approach to flexibility-in-use: Adaptability of structural elements. Proc. SASBE 2009, 9, 15–19. 38. Leatherbarrow, D. The project of design research. In Design Innovation for the Built Environment: Research by Design and the Renovation of Practice; Routledge: Abingdon-on-Thames, UK, 2012.

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