- Email: [email protected]
To demolish or not to demolish: Life cycle consideration of repurposing buildings
Sustainable Cities and Society 28 (2017) 146–153
Contents lists available at ScienceDirect
Sustainable Cities and Society journal homepage: www.elsevier.com/locate/scs
To demolish or not to demolish: Life cycle consideration of repurposing buildings Getachew Assefa ∗ , Chelsea Ambler Faculty of Environmental Design, University of Calgary, Calgary, Alberta, Canada
a r t i c l e
i n f o
Article history: Received 9 February 2016 Received in revised form 14 September 2016 Accepted 17 September 2016 Available online 18 September 2016 Keywords: Repurposing Life cycle assessment Buildings Built environment EcoCalculator Impact categories Greenhouse gases Sustainability
a b s t r a c t Reduction in energy and resource consumption, as well as other environmental impacts, can be achieved for end of life building stock by recovering building waste after demolition through material reuse and recycling; or building repurposing through selective deconstruction and building system reuse. This research investigates and compares the potential life cycle environmental impacts of building repurposing through reuse of structure and demolition scenarios followed by new construction involving an existing library tower. New building design variations, with and without a Trombe wall, are detailed for both types of scenarios. The Athena EcoCalculator for Commercial Assemblies was used in analysis of life cycle stages of resource extraction and construction; maintenance, repair, and replacement of building assemblies; and disposal. Impacts from energy consumption for building operations were not included. Repurposing scenarios showed a potential reduction, between 20 and 41%, in six of the seven environmental impact categories assessed. The highest reduction is achieved for the Eutrophication Potential followed by Smog Potential at 37% reduction. Human Health Criteria is the impact category with the least reduction at 20% followed by Acidification Potential at 29%. Global Warming Potential and Fossil Fuel Consumption which are closely correlated show an avoided impact of 33 and 34% respectively as a result of the decision to go for repurposing after selective deconstruction rather than complete demolition and new construction. The benefits of repurposing compared to new construction demolition go beyond avoided environmental impacts. Comprehensive consideration of all relevant factors pertinent to the local context is also discussed. © 2016 Elsevier Ltd. All rights reserved.
1. Introduction The built environment is a maker and breaker of sustainability efforts in many countries of the world. Infamously known as the forty-percent sector, the building sector is responsible for 40% of the global energy and resource consumption (UNEP, 2016). One-third of global greenhouse gas emissions is also attributable to the same sector. Existing building stock in Canada, is associated with 50% of natural resource extraction, 35 of greenhouse gas emissions, 33% of energy consumption, 25% of landfill waste, as well as 10% of particulate matter (ISEDC, 2015). Commercial and institutional (C&I) buildings in Canada number between 443 413 and 521 119 (NRC, 2013) and contribute to the majority of these impacts. C&I buildings therefore present an opportunity area for targeted and meaningful action to reduce overall impact of the built environment. Efforts of
∗ Corresponding author at: 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada. E-mail address: [email protected] (G. Assefa). http://dx.doi.org/10.1016/j.scs.2016.09.011 2210-6707/© 2016 Elsevier Ltd. All rights reserved.
dealing with different scales of environmental problems will succeed if the contribution of buildings and associated infrastructure is considered in earnest. The literature is full of recommendations for minimizing the environmental impact of the built environment. The quest for sustainability in different sectors of the economy including the built environment are better understood and researched using broader economy-wide concepts such as Circular Economy and place-based material and energy flow solutions such as Industrial Symbiosis. The use of construction and demolition waste has been investigated as part of achieving a Circular Economy in different countries (for example, Esa, Halog, & Rigamonti, 2016 in Malaysia; Smol, Kulczycka, Henclik, Gorazda, & Wzorek, 2015 in Poland). Esa et al. (2016) presented the concept of Circular Economy as a strategy for minimizing construction and demolition wastes in Malaysia. The theoretical framework developed based on this concept is meant to enable actions at three different levels, local, mid-range and global levels paying attention to aspects of construction that span from planning to demolition. In the other study from Poland, Circular Economy as used in the European Union is presented as an econ-
G. Assefa, C. Ambler / Sustainable Cities and Society 28 (2017) 146–153
omy that ideally eliminates wastes while maintaining the added value in products in a closed loop (Smol et al., 2015). As part of a journey towards a circular economy, the authors investigated the use of sewage sludge ash in the production of different construction materials such as input in bricks and tiles; raw material in cement production; and aggregates for concrete and mortar. In the context of built-up areas such as university campuses where a group of buildings can be gainfully connected with the objective of increasing area-wide efficiencies by harnessing existing energy and materials flows that are conventionally managed, or rather mismanaged, at individual building level. The concept of Industrial Symbiosis can be used to frame the important enablers by improving the factors that affect the flows and engaging relevant stakeholders to realize an effective utilization of resources and minimization of waste. For public policy-makers and corporate decision-makers, understanding the relative magnitude of environmental impacts and resource consumption of processes and products helps in terms of identifying where and when to intervene and what to prioritize when devising policy instruments and embarking on new product development. Rohn, Pastewski, Lettenmeier, Wiesen, and Bienge (2014) identified over 250 resource-efficient technologies, strategies and products using literature review and expert-based evaluation. After selecting 22 areas for further life cycle based analysis and assessment, the authors concluded that there is a significant resource efficiency potential expressed in the form of material footprint. There are also studies that focus on broad aspects of sustainable construction (Sfakianaki, 2015), others on use of life cycle studies (Chau, Leung, & Ng, 2015; Dadhich, Genovese, Kumar, & Acquaye, 2014). Based on a literature review on the area of construction, Sfakianaki (2015) has emphasised the role of coordinated supply chain action in the construction sector and the need for construction companies to train and invest in resource- efficient building methods and practices. The author remarked the need for commitment of all stakeholders and new ways in managing and implementing sustainability. Dadhich et al. (2014) examined the issue of developing sustainable supply chains in the UK taking the case of plaster board supply chain using life cycle assessment to identify hotspots. With a focus on types of life cycle studies used in evaluating the environmental impacts of building construction, Chau et al. (2015) compared Life Cycle Assessment (LCA), Life Cycle Energy Assessment (LCEA) and Life Cycle Carbon Emissions Assessment (LCCO2A) based on their objectives, methodologies, and findings. One area of focus in addressing the environmental impacts of buildings that is widely published is proper management of building waste. Significant resource and energy can be conserved, and other environmental impacts avoided, when building waste is recovered or recycled (Dodoo, Gustavsson, & Sathre, 2009; Roussat, Mehu, & Dujet, 2009; Scheuer, Keoleian, & Reppe, 2003; Thormark, 2001, 2006). This, however, is limited to the construction and demolition phases of buildings (Yeheyis, Hewage, Alam, Eskicioglu, & Sadiq, 2013). Another line of endeavor is the field of modular offsite construction which, when compared to conventional onsite construction, has shown reduced in construction waste, energy consumption, and transportation emissions (Al-Hussein, Manrique, & Mah, 2009; Jaillon, Poon, & Chiang, 2009).Whole building modular prefabrication works well within the residential building sector and is a good way of reducing the environmental impact of buildings where offsite construction is a viable alternative to new onsite construction. There are practical hindrances for whole building modular offsite construction for high-rise commercial and institutional buildings. Besides, most of the buildings needed for decades to come in many developed countries are already built. In these countries, the turnover of the building stock is slow and the magni-
147
tude of new construction compared to existing building stock is less than 2% (e.g. AutoDesk, 2015; Gursel 2010). According to Natural Resources Canada (NRC, 2013) 27% of commercial and institutional buildings in the country were 50 years old. Thus, reducing the environmental footprint of these old buildings and in general the whole built environment calls for a scaled-up focus on improving the performance of existing building stock. Prolonging the useful lifetime of an existing building by adapting it to new requirements of a different use can potentially save material, embodied energy, and transport related impacts when compared to new construction. Research in this area has mainly focused on either retrofitting within the lifetime of a building (Mata, Kalagasidis, & Johnsson., 2010) or reuse of disassembled materials in a second life (Gao, Ariyama, Ojima, & Meier, 2001). A preliminary study carried by Wondimagegnehu and Urness (2012) cited around 12–15% potential reduction in energy consumption based on studies residential buildings by Gao et al. (2001) and asserted that this can be further increased if remaining construction materials include recycled products. An additional benefit associated with repurposing buildings with some level of renovation and adaptation is the avoidance of the development of new land for new construction. This merit is particularly important in institutions such as universities with limited access to land in the same location where they currently operate. Interest on research around the implications of repurposing old buildings has increased over the past two decades. The literature uses the concept of adaptive reuse which is synonymous with the repurposing concept referred to in this paper. Repurposing and adaptive reuse imply retaining the major part of the original building such as the structure while upgrading other parts to suit new standards and changing user requirements (Bullen, 2007). During the course of the upgrading activity, old materials and building components are changed and higher energy efficiency is sought. As more repurposing projects are realized, there is an increasing need to understand more about the life cycle performance of the material dimension and implication of the process of repurposing buildings. This life cycle focus on materials becomes more relevant specifically as we move toward energy efficient buildings as the material component in the form of embodied impact becomes increasingly important. Understanding repurposing projects as giving new life to buildings, where embodied impacts can remain locked, will lead to innovative approaches from the design boards to the facility management boards. There is, however, a recognition that not every building will be good enough for repurposing. Bullen (2007) has a list of factors that are considered to pose challenges in furthering adaptive reuse (see also Bullen & Love, 2010; Yung & Chan, 2012). Making the case for adaptive reuse of buildings as a way of contributing to the sustainability of the built environment is not rare (e.g. Conejos, Langston, & Smith, 2015; Langston, Wong, Hui, & Shen, 2008). Examining the merits and demerits of repurposing versus complete replacement by new construction in terms of reduction in material and embodied energy and other impacts will help in making informed decision as to what is best in a specific circumstance. The fact that buildings are designed and constructed to respond to a local climatic condition alludes to the vitality of appreciating the geographic differences before one is tempted to transpose results from research done in one place to another. Many of the available studies are on the repurposing of heritage or historical buildings (Yung & Chan, 2012; Wang & Zeng, 2010). Very few have been done on commercial buildings (Jagarajan et al., 2015). There is thus a need for adding to the existing body of knowledge surrounding the environmental implications of repurposing projects compared to new constructions for the C&I building sector. Moreover, studies of cold region locations, such as the province of Alberta in Western Canada, are nonexistent.
148
G. Assefa, C. Ambler / Sustainable Cities and Society 28 (2017) 146–153
The objective of this research is, thus, to investigate the potential environmental impacts associated with reusing the structure of a high-rise building in a repurposing project. The case study building is a thirteen-story library tower at the University of Calgary in Western Canada which is under consideration for repurposing into mainly an administration building. The purpose of this study is to present a comparative analysis of the potential impacts associated with different scenarios dealing with the end-of-life of the case study building. At the time of the repurposing consideration, failure in some building elements and obsolescence in mechanical and electrical systems were observed and could not be addressed through conventional renovation methods. However, the building structure of the old library tower was found to be sound and could support repurposing where the building envelop, mechanical system, and electrical system were replaced and substantial interior modifications completed.
Table 1 Building System Details. Building System
Description
exterior walls
Typical cladding is a consistent pattern of glazing, concrete panels, and metal spandrels. Main floor facade consists of glazing and brickwork. Panel details: 4” precast wall panels, 1 1/2” air space, building paper membrane, 1/2” exterior gypsum sheathing, 6” steel stud @ 16” o.c., 2” batt insulation (fiberglass), 2 mil poly vapor barrier, interior wall (originally 3/4” plaster though re-finished in areas with painted gypsum). Glazing details: sealed units with butyl tape between glass lite and frame, rubber gaskets between interior glass lite and frame, double glazed units with some operable unit. Spandrel details: 3 3/4” plywood panels with 18ga aluminum with galvanized steel 26ga on backside, each vertical strip window has two vision units and one spandrel panel.
structure
Poured concrete structural core at center containing mechanical, washrooms, stairs, and elevators. The core extends to the thirteenth, mechanical floor, with some portions extending to the mechanical penthouse. Twenty-four exterior concrete columns extend to the twelfth floor. Twenty-four poured concrete columns at exterior extending to the thirteenth floor. Profile tapers with elevation. Intermediate floors are post-tensioned concrete slabs.
roofing
A portion of the mechanical floor is roofed. Additional roofing for the twelfth floor and penthouse. Poured concrete, Sarnafil membrane inverted roofing, and conventional 4-ply built-up asphalt roofing.
interior walls
Partitions with metal stud/drywall/ceramic tile lobby and washrooms/corridors vinyl-covered drywall on steel studs/other painted drywall on steel studs/some glass block partitions.
footprint
Building footprint is 117 × 117 ft. Columns create a twelve unit grid around the structural core.
2. Methodology The method behind the tool used in this study is life cycle assessment (LCA). A life cycle perspective can assist in understanding the potential benefits and environmental impacts of the repurposing project with the goal of informing future building stock management. 2.1. Life cycle assessment tool This LCA employed the Athena EcoCalculator 3.7.1 (referred to as EcoCalculator hereafter) for high-rise commercial building assemblies (AISM, 2015). It derives data from another tool, Athena Impact Estimator for buildings developed by the same institute, Athena Sustainable Materials in Ottawa. Users select building assemblies from the calculator and input inventory quantities in the form of square footage of assemblies. The calculator includes life cycle stages of resource extraction and construction; maintenance, repair, and replacement of building assemblies; and disposal. EcoCalculator does not assess impacts from operating energy. As the focus of the research is to provide quick directional results on the material dimension of the building, this choice of tool makes sense even with the exclusion of the energy consumption during the use phase. EcoCalculator is a midpoint impact assessment tool which includes seven environmental impact categories: Fossil Fuel Consumption (FFC), Global Warming Potential (GWP), Acidification Potential (AP), Human Health Criteria (HHC), Eutrophication Potential (EP), Ozone Depletion Potential (ODP), and Smog Potential (SP). 2.2. Case study description The library tower, known as Mackimmie Library Tower (MLT), was built in phases between 1968 and 1971 as an extension to the Mackimmie Library Block (MLB) connected by a linking structure. Originally, its foundation and structure was designed and built to support additional floors on top of its current thirteen floors. Although there is the possibility that the library link and MLB structures will be similarly reused and repurposed only the MLT is examined here as it is the largest component of the project. Until it ceased to function as a library in 2010, the tower housed library collections as well as study and administrative spaces on twelve floors. Further building system details about the MLT are provided in Table 1. The system boundary of the analysis is geographically delimited to the City of Calgary in the Province of Alberta, Canada. In terms of data used, this boundary delimitation implies that local and regional factors such as the way building materials are man-
ufactured, the electricity mix used in manufacturing and material transport distances are all applicable for the location of the building. Not all assemblies were inventoried and some were not included in the EcoCalculator. The tool has a total of 160 alternative assemblies to represent a building. Columns and Beams have 11 and 12 assemblies depending on whether a non-load bearing or loadbearing external walls are assumed. External walls, Intermediate floors and Roofs have 41, 28 and 55 alternative assemblies to choose from in that order. The EcoCalculator provides 6, 2 and 5 possible assemblies for Foundation and footings, Windows and Internal walls respectively. The inventory of assemblies for the building in this case was focused on 10 assemblies within the EcoCalculator. For those assemblies that were not included in the tool, assemblies with similar materials and components were substituted where possible. Table 2 details the building assembly inventory and associated substitutions made for missing components. The pre-cast concrete column covers were excluded from the analysis as there were no appropriate substitutions available within the Athena EcoCalculator. A substitution may have been made similar to that used for the concrete panels. However, these assemblies include insulation and steel frame components, neither of which is required for the column cover assemblies. Such a substitution would have greatly overestimated the impacts associated with this assembly. 2.3. Scenarios analyzed The scenarios considered were selected based on the early design documents that accounted for broader alternatives focusing on the two pathways: selective deconstruction and new construction. A detailed design analysis based on different material and
G. Assefa, C. Ambler / Sustainable Cities and Society 28 (2017) 146–153
149
Table 2 Assembly Substitutions (existing building). Building System
Documented details
Substitution
exterior walls
concrete panels
glazing
Precast concrete cladding + R-7.5 continuous insulation sheathing + 2 × 4 steel stud 16” o.c. R-13 cavity insulation + polyethylene membrane + gypsum board + latex paint Curtainwall metal spandrel panel with insulated backspan Steel cladding + concrete block + continuous insulation + polyethylene membrane Brick cladding + R-7.5 continuous insulation sheathing + 2 × 4 steel stud 16” o.c. + R-13 cavity insulation + polyethylene membrane + gypsum board + latex paint Aluminum double-pane, Low-E, Argon-filled
structure
foundation wall foundation slab precast concrete column/core floor structure
Concrete block R-7.5 XPS continuous insulation 4” poured concrete slab Concrete column/concrete beam suspended concrete slab
roof
mechanical floor and 12th floor roof
4-ply built-up roofing systems + R-20 continuous insulation + polyethylene membrane + suspended concrete slab + latex paint Standing seam metal roofing + metal roof panel assembly + cavity insulation
spandrels mechanical floor metal cladding brick cladding
penthouse roof
Table 3 Inventory of building assemblies accounted for the four scenarios. Building System
Scenario 1a
Scenario 1b
Scenario 2a
Scenario 2b
Foundations & footings foundation walls (ft2) foundation slab (ft2) footings (yd3)
12 200 26 912 2383
12 200 26 912 2383
6100 13 456 1191
6100 13 456 1191
Column & beams supported area (ft2)
337 896
337 896
168 948
168 948
Intermediate floors area (ft2)
310 978
310 978
155 489
155 489
Exterior walls brick (ft2) metal sheeting (ft2) spandrels (ft2) concrete panels (ft2) curtain wall (ft2)
2163 13 593 23 551 38 258 34 909
2163 13 593 23 551 38 258 34 909
2163 13 593 23 551 38 258 34 909
2163 13 593 23 551 38 258 34 909
Windows aluminum framed (ft2) curtain wall (ft2)
16 629 18 797
16 629 30 083
16 629 18 797
16 629 30 083
Roofs Suspended concrete slab (ft2) metal sheeting (ft2)
29 888 2970
29 888 2970
29 888 2970
29 888 2970
Table 4 Avoided impacts associated with structure reuse compared to new construction (without Trombe wall). Avoided Impact
Value
FFC (GJ) GWP (tonnes CO2 eq) AP (mol H + eq) HHC (kg PM10 eq) EP(kg N eq) ODP (mg CFC-11 eq) SP (kg NOx eq)
38 395 3384 1 185 013 11 930 1595 22 328 758
energy solutions was postponed by the design team for a later stage as it required to be considered in tandem with potentially available funding to carry out either of the major alternatives. Thus the selection of the scenarios for this study was limited to the material element for which two major alternative scenarios were considered. Scenario 1 represents complete demolition followed by new construction. Scenario 2 maintains the structure of the building for reuse in a repurposing context. Both scenarios have variations as presented below.
Scenario 1a: New Construction without Trombe Wall In this scenario, the tower is demolished and a new building takes its place. The new building has a 35% window to wall ratio beginning from a 3 ft sill to the ceiling at each floor. The main floor has 100% glazing. A curtainwall glazing system is assumed for the exterior wall system. For the new building: • Same foundation and structural assemblies as the original MLT are assumed • Same footprint and elevation is assumed • Same roofing system is assumed Scenario 1b: New Construction with Trombe Wall This scenario is the same as Scenario 1a above, with the addition of a Trombe wall on the Southeast to Southwest elevations of the new building. The Trombe wall begins on the seventh floor, extends to twelfth floor and is 100% single pane glazing. There are no building assemblies available in EcoCalculator which approximate a single paned Trombe wall. An aluminum frame window system is used as a substitute.
150
G. Assefa, C. Ambler / Sustainable Cities and Society 28 (2017) 146–153
Scenario 2a: Selective Deconstruction and Reuse without Trombe Wall This scenario considers selective deconstruction of the MLT. The structure is reused; all other building assemblies are disposed of and replaced by new building elements according to the new design. • The EcoCalculator includes maintenance, repairs, replacement, and disposal over a 60 year span. It is assumed that all disposed building components have reached the end of their lifespan. • The reused structure is assumed to be functional for the 60 year lifespan of the new building elements. Scenario 2b: Selective Deconstruction and Reuse with Trombe Wall This is same as Scenario 2a above, with the addition of a Trombe wall to the repurposed building. Building assembly quantities were derived from construction drawings and associated AutoCad drawings. Table 3 compares the inventory figures for the four scenarios. The values in Table 3 represented the average area (square footage) of the assembly required except for the footing which in this case is the volume of concrete required in cubic yards. For example, when different square footages of the same type of assembly is used in different floors, the average square footage across all intermediate floors is used for the calculation. As long as design and other technical requirements allow, the lower the square footage and volume of the concrete, the better in terms of environmental impacts. 3. Results When comparing options for new construction with selective deconstruction and repurposing, repurposing outperforms in six out of seven impact categories, the exception being ozone layer depletion which hardly shows a difference (Fig. 1). The figure considers the total environmental impacts of all the scenarios. Results are shown as a percentage of Scenario 1a. It not only depicts the relative impacts of each scenario but also allows all impact categories to be examined simultaneously as each has a different unit of measure. Most avoided impacts occur in the categories of EP, SP, and GWP. This can be attributed to the resource savings involved with reusing structural elements. Scenario 2a avoided 38.4 Terajoule of fossil fuel consumption. To put this figure in perspective, it is equivalent to the average monthly natural gas consumption by the University of Calgary’s cogeneration plant for electricity as calculated from data for the period of April 2014 to March 2015. The scenario also avoided 3 389 t of CO2 eq of Global Warming Potential compared to a scenario with complete demolition followed by new construction. This amount of greenhouse gas emission is closely comparable to a quarter of the emissions attributed to the commuting of faculty and staff of the University of Calgary in 2008/2009. See Table 4 for a complete listing of avoided impacts from all impact categories for Scenario 2a relative to Scenario 1a. Larger values of avoided impact in Table 4 implies a positive impact of structure reuse. How large it should be to justify a decision of reuse over new construction is a subject of further research as it requires a cumulative knowledge of similar studies and is subjected to local circumstances. Ozone depletion potential was the only impact category which was not greatly influenced by building reuse. Assemblies contributing to this category mostly involved windows and exterior wall assemblies which are comparable in all scenarios. If Ozone Depletion Potential is excluded, avoided impacts due to reuse of structure ranged from 20 to 41% of those potentially produced should the MLT be completely demolished and replaced by a new
construction. Considering all seven impact categories, average and median savings were 28% and 33% respectively. As the Trombe wall requires additional material resources, the two scenarios with the Trombe wall showed environmental impacts 1–9% higher than their counterparts, the average and median of which was 4 and 3% respectively. The intermediate floors are the largest contributors for five of the seven impact categories in the complete demolition followed by new construction, Scenario 1a (Table 5). In the selective deconstruction and repurposing scenario, Scenario 2a, a similar pattern of contribution is observed where different building components contribute to varying degrees. Both scenarios have the same building component (s) as highest contributors for each impact category (shown as bold in both tables). An exception is for Acidification Potential while Intermediate Floors are the highest contributors in Scenario 1a, Windows (glazing and metal sheeting) appear as the largest contributor in Scenario 2a (see Table 6 below). Table 7 shows the environmental impact associated with the Trombe wall. The contribution from this building system is the same for both the new construction and the selective deconstruction scenarios.
4. Discussion The main purpose of the research was to get a quick estimate of the differences between a complete demolition followed by new construction and selective deconstruction of the building followed by repurposing scenarios. The EcoCalculator was preferred for this analysis as it is a simplified tool capable of giving quick results suitable for early stage design table discussions where there are few resources and requirements for detailed analysis. The results fulfill the purpose of identifying the best alternative and allow later further analysis to then focus on the impact of different individual components, materials, and designs options. Data used was limited to materials used in the different parts of the building under each scenario as read from drawings and obtained from construction documents through the Architecture unit of the Facilities Management of the University. The selective deconstruction and repurposing scenarios show 20% to 41% less impact in six out of seven environmental impact categories assessed. The highest reduction is achieved for Eutrophication Potential followed by Smog Potential at 37% reduction. Out of the six categories that showed significant difference, Human Health Criteria is the least reduction at 20% followed by Acidification Potential at 29%. Due to the close correlation between Global Warming Potential and Fossil Fuel Consumption, both show an avoided impact of 33 and 34% respectively associated with the University’s decision to go for repurposing after selective deconstruction rather than complete demolition and new construction. The role of Trombe wall is insignificant in terms of increasing the magnitude of most of the impact categories. The relatively significant increase is only seen for the Human Health Criteria at 9%. Overall despite its contribution to the impact categories, it shows no influence in changing the overall ranking of the scenarios. Comparing the outcome of this analysis with similar analysis in the literature in terms of the reduction in impacts of reuse of structure versus new construction is important even though each building is unique in different ways and it is difficult to find studies done for the same type of building in the same climatic zone. The general findings of this study are in agreement with that of a study done by Vandenbroucke, Galle, De Temmerman, Debacker, and Paduart (2015) on student residences in Belgium that concluded from a life cycle perspective the reuse and transformation of the student resi-
G. Assefa, C. Ambler / Sustainable Cities and Society 28 (2017) 146–153
151
Table 5 Percentage contribution of different building elements for the seven impact categories in Scenario 1a. Building Systems
FFC (MJ)
GWP (tonnes CO2 eq)
AP (mol H+ eq)
HHC (kg PM10 eq)
EP (g N eq)
ODP (mg CFC-11 eq)
SP (kg NOX eq)
Foundation &Footings Columns & Beams Intermediate Floors Exterior Walls Windows Roof Total
8% 25% 33% 14% 11% 9% 100%
9% 21% 37% 15% 12% 5% 100%
8% 18% 32% 18% 20% 4% 100%
6% 10% 23% 23% 33% 4% 100%
8% 36% 37% 9% 6% 4% 100%
≈0% ≈0% ≈0% 59% 31% 9% 100%
11% 17% 46% 10% 11% 5% 100%
Bold values show the highest contributing building system(s).
Fig. 1. Impact assessment results of scenarios relative to Scenario 1a.
Table 6 Percentage contribution of different building elements for the seven impact categories in Scenario 2a. Building Systems
FFC (MJ)
GWP (tonnes CO2 eq)
AP (mol H+ eq)
HHC (kg PM10 eq)
EP (g N eq)
ODP (mg CFC-11 eq)
SP (kg NOX eq)
Foundation &Footings Columns & Beams Intermediate Floors Exterior Walls Windows Roof Total
6% 18% 25% 22% 16% 13% 100%
7% 16% 28% 23% 18% 8% 100%
5% 12% 23% 25% 29% 6% 100%
4% 6% 14% 29% 41% 5% 100%
7% 30% 31% 15% 10% 7% 100%
0% 0% 0% 59% 31% 9% 100%
9% 14% 36% 15% 18% 8% 100%
Bold values show the highest contributing building system(s).
dences compared to demolition and rebuilding have a significantly lower impact. The findings are limited for the scenarios characterized in terms of the early versions of the repurposing documents. As the project is pushed up for potential provincial funding, the materials and assemblies of the repurposing project will be more detailed which is not the case for the data used in this research. The EcoCalcu-
lator does not account for the use phase in terms of operational energy use of buildings. Assumptions made in the development of the comparative scenarios may have influenced results. In Scenario 1a, it is assumed that the new building would occupy the same footprint and have the same number of floors as the currently standing library tower. In addition, it would also be based on the same foundation and structural assemblies. As the library tower
152
G. Assefa, C. Ambler / Sustainable Cities and Society 28 (2017) 146–153
Table 7 Environmental Impacts of Trombe Wall. Impact
Value
FFC (GJ) GWP (tonnes CO2eq) AP (mol H+ eq) HHC (kg pm 2.5 u eq) EP (g N eq) ODP (mg CFC −11 eq) SP (kg Nox eq)
2273 281 156 199 5596 55 171 553 23 646
was originally designed to be completed in phases to twenty-one stories (i.e. not limited to thirteen stories as in its current state) and to be loaded with library materials it is likely that the contribution of structural elements overestimate those encountered in new construction for buildings of similar size and different purpose. A single pane glass Trombe wall building assembly, as specified in the repurposing designs, was not available in the EcoCalculator. The curtain wall building assembly was used as a substitute. This may overestimate the impact of the Trombe wall as it includes a double pane system. Finally, interior walls and other building systems were omitted or could not be included due to the limits of the EcoCalculator. Again, this likely leads to an underestimation of associated environmental impacts. In particular, pre-cast concrete column coverings were detailed in the construction drawings however, a suitable substitute could not be identified. Due to the limitation associated with the tool used and the data employed, the results obtained are better interpreted in the context of capturing the relative order of magnitude performance difference in comparing selective deconstruction versus demolition and new construction. The results are limited to provision of directional outcome focusing on the material component of the building. It is therefore limited as it excludes the energy consumption during the life span of the building. The results obtained that are based on average regional and local data are not to be used as a replacement for an outcome that is based on a fully detailed life cycle assessment using specific material and energy data. Due to its objectives of getting quick results using the limited data and information available at early stage of design discussions, the study has not included uncertainty analysis. 5. Conclusion and recommendation To have an idea of the large scale implication of the reduction figures, if only 10% of the close to half a million commercial and institutional buildings in Canada can be repurposed in a second life thus avoiding the need to replace them with new buildings and thereby achieve on average the avoidance of a Global Warming Potential around 3 300 t per repurposed building as is in the case study building, this would imply preventing the emission of 165 megatonnes of CO2 equivalent to the atmosphere. This prevented emission is significantly higher than the 130 megatonnes of emission from all human activities in nine of the thirteen provinces and territories in Canada in 2013. This represents around 23% of total Canadian GHG emissions the same year. As the University of Calgary celebrates its 50 years milestone this year (2016), close to 25 of its buildings are at least 40 years old, thus approaching the end of their functional lifespan. The result from this study, though specific to the case study building, will hopefully be useful in informing discussions around the fate of many of these old buildings. The loss of these buildings will surely add to the already present need for additional learning, research, and administrative space to accommodate an active and growing university (Wondimagegnehu & Urness, 2012). However, the same build stock also presents the opportunity to achieve better envi-
ronmental and other desired benefits if handled in a holistic way. When the buildings were built four decades ago, there is perhaps no doubt that they were fit for their purpose of the time. In the decades to come, it would be imperative to consider the best ways of increasing functional spaces within the existing stock as land will be increasingly limiting in terms of expansion through new construction. Hence the question of demolition and construction or renovation and repurposing will be not only of environmental importance but also of economic and practical significance. The economic and practical aspects, not considered in this study, are related to the time it takes to turn the building site around and the resultant disruption on surrounding activities. Reuse of a building structure reduces the volume of construction waste to be removed and eliminates some of the need for site remediation before new construction. In doing these and in bypassing construction of the structure, overall construction time could be shortened. Selective deconstruction of a building may also allow sections of the building to remain operational for the duration potentially reducing the impact of deconstruction and construction on the surrounding community of users. Obviously, due to the long lifetime of buildings, there is an inherent difficulty of predicting use type changes during the course of their lifetime. However, it is prudent for designers and developers to design-in flexibility in terms of future possible changes in use of new constructions. Universities face significant challenges as they aspire to enhance their teaching and research activities while increasing their intake capacity and financing capital projects that support the expansion. At the same time, compared to other institutions, universities have better potential to account for future use change of their new buildings already at the design board. It will be important for facility development and management entities to embrace comprehensive studies that explore different options as they navigate through the development and operational aspects of buildings and non-building infrastructure. Legacy impacts should be dealt with properly alluding to local contexts and after a holistic consideration of all relevant factors comprehensively (e.g. Sfakianaki & Moutsatsou, 2015). The local context captures, among others, the role of climatic variables as repurposing buildings in a cold climate region may not, for example, be the same as those in a hot climate region. Research focusing on the trade-off between the benefit of achieving higher performance through new construction and the additional differential embodied impacts should be carried out. In line with the aforementioned limitations of the EcoCalculator and the focused scope of this research, a life cycle assessment covering both the use phase and detailed end-of-life phase based on data from advanced design documents is recommended.
Acknowledgements The authors would like to acknowledge the contribution of the Alberta Innovates – Bio Solutions for providing the funding to the Athena Chair in Life Cycle Assessment at the Faculty of Environmental Design, University of Calgary.
References AISM. (2015). EcoCalculator: overview. Accessed on December 2015 on. http:// calculatelca.com/software/ecocalculator/overview/ Al-Hussein, M., Manrique, J. D., & Mah, D. (2009). North Ridge CO2 analysis report: Comparison between modular and on-site construction. Canada: University of Alberta. AutoDesk. (2015). Congress members look at the reinventing existing buildings.. Accessed on January 2016 at. http://sustainability.autodesk.com/blog/ reinventing-existing-buildings-nbi/ Bullen, P. A., & Love, P. E. D. (2010). The rhetoric of adaptive reuse or reality of demolition: Views from the field. Cities, 27(4), 215–224.
G. Assefa, C. Ambler / Sustainable Cities and Society 28 (2017) 146–153 Bullen, P. A. (2007). Adaptive reuse and sustainability of commercial buildings. Facilities, 25(1/2), 20–31. Chau, C. K., Leung, T. M., & Ng, W. Y. (2015). A review on life cycle assessment, life cycle energy assessment and life cycle carbon emissions assessment on buildings. Applied Energy, Vol. 143(No. C), 395–413. Conejos, S., Langston, C., & Smith, J. (2015). Enhancing sustainability through designing for adaptive reuse from the outset: A comparison of adaptSTAR and Adaptive Reuse Potential (ARP) models. Facilities, 33(9/10), 531–552. Dadhich, P., Genovese, A., Kumar, N., & Acquaye, A. (2014). Developing sustainable supply chains in the UK construction industry: A case study. International Journal of Production Economics, 164(June), 271–284. Dodoo, A., Gustavsson, L., & Sathre, R. (2009). Carbon implications of end-of-life management of building materials. Conservation & Recycling, 53(5), 276–286. Esa, M. R., Halog, A., & Rigamonti, L. (2016). Developing strategies for managing construction and demolition wastes in Malaysia based on the concept of circular economy. Journal of Material Cycles and Waste Management, 1–11. Gao, W., Ariyama, T., Ojima, T., & Meier, A. (2001). Energy impacts of recycling disassembly material in residential buildings. Energy & Buildings, 33(6), 553–562. Gursel, I. (2010). CLIP: Computational support for lifecycle integral building performance assessment. Accessed on January 2016 at. https://toi.bk.tudelft.nl/ designInformatics/index.php/phd-research/clip/ ISEDC. (2015). Corporate social responsibility: SME sustainability roadmap. Innovation, Science and Economic Development Canada (ISEDC).. Accessed on January 29, 2016 at. https://www.ic.gc.ca/eic/site/csr-rse.nsf/eng/rs00585.html Jagarajan, R., Abdullah, M. N., Asmoni, M., Mei, J. L. Y., Misnan, M. S., Jaafar, M. N., et al. (2015). A review on critical success factors of sustainable retrofitting implementation. Jurnal Teknologi, 74(2). Jaillon, L., Poon, C. S., & Chiang, Y. H. (2009). Quantifying the waste reduction potential of using prefabrication in building construction in Hong Kong. Waste Management, 29, 309–320. Langston, C., Wong, F. K. W., Hui, E. C. M., & Shen, L.-Y. (2008). Strategic assessment of building adaptive reuseopportunities in Hong Kong. Building and Environment, 43(10), 1709–1718. Mata, E., Kalagasidis, A. S., & Johnsson, F. (2010). Retrofitting measures for energy savings in the Swedish residential building stock – Assessing methodology. In Thermal performance of the exterior envelopes of whole buildings XI International Conference. NRC. (2013). Survey of commercial and institutional energy use: Buildings 2009 summary report. Ottawa, Ontario, Canada: Natural Resource Canada’s (NRC) Office of Energy Efficiency. Rohn, H., Pastewski, N., Lettenmeier, M., Wiesen, K., & Bienge, K. (2014). Resource efficiency potential of selected technologies, products and strategies. Science of the Total Environment, 473, 32–35.
153
Roussat, N., Mehu, J., & Dujet, C. (2009). Indicators to assess the recovery of natural resources contained in demolition waste. Waste Management & Research, 27(2), 159–166. Scheuer, C., Keoleian, G. A., & Reppe, P. (2003). Life cycle energy and environmental performance of a new university building: Modeling challenges and design implications. Energy & Buildings, 35(10), 1049–1064. Sfakianaki, E., & Moutsatsou, K. (2015). A decision support tool for the adaptive reuse or demolition and reconstruction of existing buildings. Int. J. Environment and Sustainable Development, 14(1), 1–19. Sfakianaki, E. (2015). Resource-efficient construction: Rethinking construction towards sustainability. World Journal of Science, Technology and Sustainable Development, 12, 233–242. Smol, M., Kulczycka, J., Henclik, A., Gorazda, K., & Wzorek, Z. (2015). The possible use of sewage sludge ash (SSA) in the construction industry as a way towards a circular economy. Journal of Cleaner Production, 95, 45–54. Thormark, C. (2001). Conservation of energy and natural resources by recycling building waste. Resources, Conservation & Recycling, 33(2), 113–130. Thormark, C. (2006). The effect of material choice on the total energy need and recycling potential of a building. Building and Environment, 41(8), 1019–1026. UNEP. (2016). Sustainable buildings and climate initiative: Why buildings. united nations environment programme (UNEP).. Accessed on January 2016 at. http:// www.unep.org/sbci/AboutSBCI/Background.asp Vandenbroucke, M., Galle, W., De Temmerman, N., Debacker, W., & Paduart, A. (2015). Using life cycle assessment to inform decision-making for sustainable buildings. Buildings, 5(2), 536–559. Wang, H.-J., & Zeng, Z.-T. (2010). A multi-objective decision-making process for reuse selection of historic buildings. Expert Systems with Applications, 37(2), 1241–1249. Wondimagegnehu, G., & Urness, C. (2012). Repurposing a university library building ?life cycle implication. In Accepted for poster presentation but not presented at LCA XII conference held Tacoma. Accessed in January 15, 2016. http://lcacenter.org/lcaxii/abstracts/674.htm Yeheyis, M., Hewage, K., Alam, M. S., Eskicioglu, C., & Sadiq, R. (2013). An overview of construction and demolition waste management in canada: A lifecycle analysis approach to sustainability. Clean Technologies and Environmental Policy, 15(1), 81–91. Yung, E. H. K., & Chan, E. H. W. (2012). Implementation challenges to the adaptive reuse of heritage buildings: Towards the goals of sustainable, low carbon cities. Habitat International, 36(3), 352–361.
Contents lists available at ScienceDirect
Sustainable Cities and Society journal homepage: www.elsevier.com/locate/scs
To demolish or not to demolish: Life cycle consideration of repurposing buildings Getachew Assefa ∗ , Chelsea Ambler Faculty of Environmental Design, University of Calgary, Calgary, Alberta, Canada
a r t i c l e
i n f o
Article history: Received 9 February 2016 Received in revised form 14 September 2016 Accepted 17 September 2016 Available online 18 September 2016 Keywords: Repurposing Life cycle assessment Buildings Built environment EcoCalculator Impact categories Greenhouse gases Sustainability
a b s t r a c t Reduction in energy and resource consumption, as well as other environmental impacts, can be achieved for end of life building stock by recovering building waste after demolition through material reuse and recycling; or building repurposing through selective deconstruction and building system reuse. This research investigates and compares the potential life cycle environmental impacts of building repurposing through reuse of structure and demolition scenarios followed by new construction involving an existing library tower. New building design variations, with and without a Trombe wall, are detailed for both types of scenarios. The Athena EcoCalculator for Commercial Assemblies was used in analysis of life cycle stages of resource extraction and construction; maintenance, repair, and replacement of building assemblies; and disposal. Impacts from energy consumption for building operations were not included. Repurposing scenarios showed a potential reduction, between 20 and 41%, in six of the seven environmental impact categories assessed. The highest reduction is achieved for the Eutrophication Potential followed by Smog Potential at 37% reduction. Human Health Criteria is the impact category with the least reduction at 20% followed by Acidification Potential at 29%. Global Warming Potential and Fossil Fuel Consumption which are closely correlated show an avoided impact of 33 and 34% respectively as a result of the decision to go for repurposing after selective deconstruction rather than complete demolition and new construction. The benefits of repurposing compared to new construction demolition go beyond avoided environmental impacts. Comprehensive consideration of all relevant factors pertinent to the local context is also discussed. © 2016 Elsevier Ltd. All rights reserved.
1. Introduction The built environment is a maker and breaker of sustainability efforts in many countries of the world. Infamously known as the forty-percent sector, the building sector is responsible for 40% of the global energy and resource consumption (UNEP, 2016). One-third of global greenhouse gas emissions is also attributable to the same sector. Existing building stock in Canada, is associated with 50% of natural resource extraction, 35 of greenhouse gas emissions, 33% of energy consumption, 25% of landfill waste, as well as 10% of particulate matter (ISEDC, 2015). Commercial and institutional (C&I) buildings in Canada number between 443 413 and 521 119 (NRC, 2013) and contribute to the majority of these impacts. C&I buildings therefore present an opportunity area for targeted and meaningful action to reduce overall impact of the built environment. Efforts of
∗ Corresponding author at: 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada. E-mail address: [email protected] (G. Assefa). http://dx.doi.org/10.1016/j.scs.2016.09.011 2210-6707/© 2016 Elsevier Ltd. All rights reserved.
dealing with different scales of environmental problems will succeed if the contribution of buildings and associated infrastructure is considered in earnest. The literature is full of recommendations for minimizing the environmental impact of the built environment. The quest for sustainability in different sectors of the economy including the built environment are better understood and researched using broader economy-wide concepts such as Circular Economy and place-based material and energy flow solutions such as Industrial Symbiosis. The use of construction and demolition waste has been investigated as part of achieving a Circular Economy in different countries (for example, Esa, Halog, & Rigamonti, 2016 in Malaysia; Smol, Kulczycka, Henclik, Gorazda, & Wzorek, 2015 in Poland). Esa et al. (2016) presented the concept of Circular Economy as a strategy for minimizing construction and demolition wastes in Malaysia. The theoretical framework developed based on this concept is meant to enable actions at three different levels, local, mid-range and global levels paying attention to aspects of construction that span from planning to demolition. In the other study from Poland, Circular Economy as used in the European Union is presented as an econ-
G. Assefa, C. Ambler / Sustainable Cities and Society 28 (2017) 146–153
omy that ideally eliminates wastes while maintaining the added value in products in a closed loop (Smol et al., 2015). As part of a journey towards a circular economy, the authors investigated the use of sewage sludge ash in the production of different construction materials such as input in bricks and tiles; raw material in cement production; and aggregates for concrete and mortar. In the context of built-up areas such as university campuses where a group of buildings can be gainfully connected with the objective of increasing area-wide efficiencies by harnessing existing energy and materials flows that are conventionally managed, or rather mismanaged, at individual building level. The concept of Industrial Symbiosis can be used to frame the important enablers by improving the factors that affect the flows and engaging relevant stakeholders to realize an effective utilization of resources and minimization of waste. For public policy-makers and corporate decision-makers, understanding the relative magnitude of environmental impacts and resource consumption of processes and products helps in terms of identifying where and when to intervene and what to prioritize when devising policy instruments and embarking on new product development. Rohn, Pastewski, Lettenmeier, Wiesen, and Bienge (2014) identified over 250 resource-efficient technologies, strategies and products using literature review and expert-based evaluation. After selecting 22 areas for further life cycle based analysis and assessment, the authors concluded that there is a significant resource efficiency potential expressed in the form of material footprint. There are also studies that focus on broad aspects of sustainable construction (Sfakianaki, 2015), others on use of life cycle studies (Chau, Leung, & Ng, 2015; Dadhich, Genovese, Kumar, & Acquaye, 2014). Based on a literature review on the area of construction, Sfakianaki (2015) has emphasised the role of coordinated supply chain action in the construction sector and the need for construction companies to train and invest in resource- efficient building methods and practices. The author remarked the need for commitment of all stakeholders and new ways in managing and implementing sustainability. Dadhich et al. (2014) examined the issue of developing sustainable supply chains in the UK taking the case of plaster board supply chain using life cycle assessment to identify hotspots. With a focus on types of life cycle studies used in evaluating the environmental impacts of building construction, Chau et al. (2015) compared Life Cycle Assessment (LCA), Life Cycle Energy Assessment (LCEA) and Life Cycle Carbon Emissions Assessment (LCCO2A) based on their objectives, methodologies, and findings. One area of focus in addressing the environmental impacts of buildings that is widely published is proper management of building waste. Significant resource and energy can be conserved, and other environmental impacts avoided, when building waste is recovered or recycled (Dodoo, Gustavsson, & Sathre, 2009; Roussat, Mehu, & Dujet, 2009; Scheuer, Keoleian, & Reppe, 2003; Thormark, 2001, 2006). This, however, is limited to the construction and demolition phases of buildings (Yeheyis, Hewage, Alam, Eskicioglu, & Sadiq, 2013). Another line of endeavor is the field of modular offsite construction which, when compared to conventional onsite construction, has shown reduced in construction waste, energy consumption, and transportation emissions (Al-Hussein, Manrique, & Mah, 2009; Jaillon, Poon, & Chiang, 2009).Whole building modular prefabrication works well within the residential building sector and is a good way of reducing the environmental impact of buildings where offsite construction is a viable alternative to new onsite construction. There are practical hindrances for whole building modular offsite construction for high-rise commercial and institutional buildings. Besides, most of the buildings needed for decades to come in many developed countries are already built. In these countries, the turnover of the building stock is slow and the magni-
147
tude of new construction compared to existing building stock is less than 2% (e.g. AutoDesk, 2015; Gursel 2010). According to Natural Resources Canada (NRC, 2013) 27% of commercial and institutional buildings in the country were 50 years old. Thus, reducing the environmental footprint of these old buildings and in general the whole built environment calls for a scaled-up focus on improving the performance of existing building stock. Prolonging the useful lifetime of an existing building by adapting it to new requirements of a different use can potentially save material, embodied energy, and transport related impacts when compared to new construction. Research in this area has mainly focused on either retrofitting within the lifetime of a building (Mata, Kalagasidis, & Johnsson., 2010) or reuse of disassembled materials in a second life (Gao, Ariyama, Ojima, & Meier, 2001). A preliminary study carried by Wondimagegnehu and Urness (2012) cited around 12–15% potential reduction in energy consumption based on studies residential buildings by Gao et al. (2001) and asserted that this can be further increased if remaining construction materials include recycled products. An additional benefit associated with repurposing buildings with some level of renovation and adaptation is the avoidance of the development of new land for new construction. This merit is particularly important in institutions such as universities with limited access to land in the same location where they currently operate. Interest on research around the implications of repurposing old buildings has increased over the past two decades. The literature uses the concept of adaptive reuse which is synonymous with the repurposing concept referred to in this paper. Repurposing and adaptive reuse imply retaining the major part of the original building such as the structure while upgrading other parts to suit new standards and changing user requirements (Bullen, 2007). During the course of the upgrading activity, old materials and building components are changed and higher energy efficiency is sought. As more repurposing projects are realized, there is an increasing need to understand more about the life cycle performance of the material dimension and implication of the process of repurposing buildings. This life cycle focus on materials becomes more relevant specifically as we move toward energy efficient buildings as the material component in the form of embodied impact becomes increasingly important. Understanding repurposing projects as giving new life to buildings, where embodied impacts can remain locked, will lead to innovative approaches from the design boards to the facility management boards. There is, however, a recognition that not every building will be good enough for repurposing. Bullen (2007) has a list of factors that are considered to pose challenges in furthering adaptive reuse (see also Bullen & Love, 2010; Yung & Chan, 2012). Making the case for adaptive reuse of buildings as a way of contributing to the sustainability of the built environment is not rare (e.g. Conejos, Langston, & Smith, 2015; Langston, Wong, Hui, & Shen, 2008). Examining the merits and demerits of repurposing versus complete replacement by new construction in terms of reduction in material and embodied energy and other impacts will help in making informed decision as to what is best in a specific circumstance. The fact that buildings are designed and constructed to respond to a local climatic condition alludes to the vitality of appreciating the geographic differences before one is tempted to transpose results from research done in one place to another. Many of the available studies are on the repurposing of heritage or historical buildings (Yung & Chan, 2012; Wang & Zeng, 2010). Very few have been done on commercial buildings (Jagarajan et al., 2015). There is thus a need for adding to the existing body of knowledge surrounding the environmental implications of repurposing projects compared to new constructions for the C&I building sector. Moreover, studies of cold region locations, such as the province of Alberta in Western Canada, are nonexistent.
148
G. Assefa, C. Ambler / Sustainable Cities and Society 28 (2017) 146–153
The objective of this research is, thus, to investigate the potential environmental impacts associated with reusing the structure of a high-rise building in a repurposing project. The case study building is a thirteen-story library tower at the University of Calgary in Western Canada which is under consideration for repurposing into mainly an administration building. The purpose of this study is to present a comparative analysis of the potential impacts associated with different scenarios dealing with the end-of-life of the case study building. At the time of the repurposing consideration, failure in some building elements and obsolescence in mechanical and electrical systems were observed and could not be addressed through conventional renovation methods. However, the building structure of the old library tower was found to be sound and could support repurposing where the building envelop, mechanical system, and electrical system were replaced and substantial interior modifications completed.
Table 1 Building System Details. Building System
Description
exterior walls
Typical cladding is a consistent pattern of glazing, concrete panels, and metal spandrels. Main floor facade consists of glazing and brickwork. Panel details: 4” precast wall panels, 1 1/2” air space, building paper membrane, 1/2” exterior gypsum sheathing, 6” steel stud @ 16” o.c., 2” batt insulation (fiberglass), 2 mil poly vapor barrier, interior wall (originally 3/4” plaster though re-finished in areas with painted gypsum). Glazing details: sealed units with butyl tape between glass lite and frame, rubber gaskets between interior glass lite and frame, double glazed units with some operable unit. Spandrel details: 3 3/4” plywood panels with 18ga aluminum with galvanized steel 26ga on backside, each vertical strip window has two vision units and one spandrel panel.
structure
Poured concrete structural core at center containing mechanical, washrooms, stairs, and elevators. The core extends to the thirteenth, mechanical floor, with some portions extending to the mechanical penthouse. Twenty-four exterior concrete columns extend to the twelfth floor. Twenty-four poured concrete columns at exterior extending to the thirteenth floor. Profile tapers with elevation. Intermediate floors are post-tensioned concrete slabs.
roofing
A portion of the mechanical floor is roofed. Additional roofing for the twelfth floor and penthouse. Poured concrete, Sarnafil membrane inverted roofing, and conventional 4-ply built-up asphalt roofing.
interior walls
Partitions with metal stud/drywall/ceramic tile lobby and washrooms/corridors vinyl-covered drywall on steel studs/other painted drywall on steel studs/some glass block partitions.
footprint
Building footprint is 117 × 117 ft. Columns create a twelve unit grid around the structural core.
2. Methodology The method behind the tool used in this study is life cycle assessment (LCA). A life cycle perspective can assist in understanding the potential benefits and environmental impacts of the repurposing project with the goal of informing future building stock management. 2.1. Life cycle assessment tool This LCA employed the Athena EcoCalculator 3.7.1 (referred to as EcoCalculator hereafter) for high-rise commercial building assemblies (AISM, 2015). It derives data from another tool, Athena Impact Estimator for buildings developed by the same institute, Athena Sustainable Materials in Ottawa. Users select building assemblies from the calculator and input inventory quantities in the form of square footage of assemblies. The calculator includes life cycle stages of resource extraction and construction; maintenance, repair, and replacement of building assemblies; and disposal. EcoCalculator does not assess impacts from operating energy. As the focus of the research is to provide quick directional results on the material dimension of the building, this choice of tool makes sense even with the exclusion of the energy consumption during the use phase. EcoCalculator is a midpoint impact assessment tool which includes seven environmental impact categories: Fossil Fuel Consumption (FFC), Global Warming Potential (GWP), Acidification Potential (AP), Human Health Criteria (HHC), Eutrophication Potential (EP), Ozone Depletion Potential (ODP), and Smog Potential (SP). 2.2. Case study description The library tower, known as Mackimmie Library Tower (MLT), was built in phases between 1968 and 1971 as an extension to the Mackimmie Library Block (MLB) connected by a linking structure. Originally, its foundation and structure was designed and built to support additional floors on top of its current thirteen floors. Although there is the possibility that the library link and MLB structures will be similarly reused and repurposed only the MLT is examined here as it is the largest component of the project. Until it ceased to function as a library in 2010, the tower housed library collections as well as study and administrative spaces on twelve floors. Further building system details about the MLT are provided in Table 1. The system boundary of the analysis is geographically delimited to the City of Calgary in the Province of Alberta, Canada. In terms of data used, this boundary delimitation implies that local and regional factors such as the way building materials are man-
ufactured, the electricity mix used in manufacturing and material transport distances are all applicable for the location of the building. Not all assemblies were inventoried and some were not included in the EcoCalculator. The tool has a total of 160 alternative assemblies to represent a building. Columns and Beams have 11 and 12 assemblies depending on whether a non-load bearing or loadbearing external walls are assumed. External walls, Intermediate floors and Roofs have 41, 28 and 55 alternative assemblies to choose from in that order. The EcoCalculator provides 6, 2 and 5 possible assemblies for Foundation and footings, Windows and Internal walls respectively. The inventory of assemblies for the building in this case was focused on 10 assemblies within the EcoCalculator. For those assemblies that were not included in the tool, assemblies with similar materials and components were substituted where possible. Table 2 details the building assembly inventory and associated substitutions made for missing components. The pre-cast concrete column covers were excluded from the analysis as there were no appropriate substitutions available within the Athena EcoCalculator. A substitution may have been made similar to that used for the concrete panels. However, these assemblies include insulation and steel frame components, neither of which is required for the column cover assemblies. Such a substitution would have greatly overestimated the impacts associated with this assembly. 2.3. Scenarios analyzed The scenarios considered were selected based on the early design documents that accounted for broader alternatives focusing on the two pathways: selective deconstruction and new construction. A detailed design analysis based on different material and
G. Assefa, C. Ambler / Sustainable Cities and Society 28 (2017) 146–153
149
Table 2 Assembly Substitutions (existing building). Building System
Documented details
Substitution
exterior walls
concrete panels
glazing
Precast concrete cladding + R-7.5 continuous insulation sheathing + 2 × 4 steel stud 16” o.c. R-13 cavity insulation + polyethylene membrane + gypsum board + latex paint Curtainwall metal spandrel panel with insulated backspan Steel cladding + concrete block + continuous insulation + polyethylene membrane Brick cladding + R-7.5 continuous insulation sheathing + 2 × 4 steel stud 16” o.c. + R-13 cavity insulation + polyethylene membrane + gypsum board + latex paint Aluminum double-pane, Low-E, Argon-filled
structure
foundation wall foundation slab precast concrete column/core floor structure
Concrete block R-7.5 XPS continuous insulation 4” poured concrete slab Concrete column/concrete beam suspended concrete slab
roof
mechanical floor and 12th floor roof
4-ply built-up roofing systems + R-20 continuous insulation + polyethylene membrane + suspended concrete slab + latex paint Standing seam metal roofing + metal roof panel assembly + cavity insulation
spandrels mechanical floor metal cladding brick cladding
penthouse roof
Table 3 Inventory of building assemblies accounted for the four scenarios. Building System
Scenario 1a
Scenario 1b
Scenario 2a
Scenario 2b
Foundations & footings foundation walls (ft2) foundation slab (ft2) footings (yd3)
12 200 26 912 2383
12 200 26 912 2383
6100 13 456 1191
6100 13 456 1191
Column & beams supported area (ft2)
337 896
337 896
168 948
168 948
Intermediate floors area (ft2)
310 978
310 978
155 489
155 489
Exterior walls brick (ft2) metal sheeting (ft2) spandrels (ft2) concrete panels (ft2) curtain wall (ft2)
2163 13 593 23 551 38 258 34 909
2163 13 593 23 551 38 258 34 909
2163 13 593 23 551 38 258 34 909
2163 13 593 23 551 38 258 34 909
Windows aluminum framed (ft2) curtain wall (ft2)
16 629 18 797
16 629 30 083
16 629 18 797
16 629 30 083
Roofs Suspended concrete slab (ft2) metal sheeting (ft2)
29 888 2970
29 888 2970
29 888 2970
29 888 2970
Table 4 Avoided impacts associated with structure reuse compared to new construction (without Trombe wall). Avoided Impact
Value
FFC (GJ) GWP (tonnes CO2 eq) AP (mol H + eq) HHC (kg PM10 eq) EP(kg N eq) ODP (mg CFC-11 eq) SP (kg NOx eq)
38 395 3384 1 185 013 11 930 1595 22 328 758
energy solutions was postponed by the design team for a later stage as it required to be considered in tandem with potentially available funding to carry out either of the major alternatives. Thus the selection of the scenarios for this study was limited to the material element for which two major alternative scenarios were considered. Scenario 1 represents complete demolition followed by new construction. Scenario 2 maintains the structure of the building for reuse in a repurposing context. Both scenarios have variations as presented below.
Scenario 1a: New Construction without Trombe Wall In this scenario, the tower is demolished and a new building takes its place. The new building has a 35% window to wall ratio beginning from a 3 ft sill to the ceiling at each floor. The main floor has 100% glazing. A curtainwall glazing system is assumed for the exterior wall system. For the new building: • Same foundation and structural assemblies as the original MLT are assumed • Same footprint and elevation is assumed • Same roofing system is assumed Scenario 1b: New Construction with Trombe Wall This scenario is the same as Scenario 1a above, with the addition of a Trombe wall on the Southeast to Southwest elevations of the new building. The Trombe wall begins on the seventh floor, extends to twelfth floor and is 100% single pane glazing. There are no building assemblies available in EcoCalculator which approximate a single paned Trombe wall. An aluminum frame window system is used as a substitute.
150
G. Assefa, C. Ambler / Sustainable Cities and Society 28 (2017) 146–153
Scenario 2a: Selective Deconstruction and Reuse without Trombe Wall This scenario considers selective deconstruction of the MLT. The structure is reused; all other building assemblies are disposed of and replaced by new building elements according to the new design. • The EcoCalculator includes maintenance, repairs, replacement, and disposal over a 60 year span. It is assumed that all disposed building components have reached the end of their lifespan. • The reused structure is assumed to be functional for the 60 year lifespan of the new building elements. Scenario 2b: Selective Deconstruction and Reuse with Trombe Wall This is same as Scenario 2a above, with the addition of a Trombe wall to the repurposed building. Building assembly quantities were derived from construction drawings and associated AutoCad drawings. Table 3 compares the inventory figures for the four scenarios. The values in Table 3 represented the average area (square footage) of the assembly required except for the footing which in this case is the volume of concrete required in cubic yards. For example, when different square footages of the same type of assembly is used in different floors, the average square footage across all intermediate floors is used for the calculation. As long as design and other technical requirements allow, the lower the square footage and volume of the concrete, the better in terms of environmental impacts. 3. Results When comparing options for new construction with selective deconstruction and repurposing, repurposing outperforms in six out of seven impact categories, the exception being ozone layer depletion which hardly shows a difference (Fig. 1). The figure considers the total environmental impacts of all the scenarios. Results are shown as a percentage of Scenario 1a. It not only depicts the relative impacts of each scenario but also allows all impact categories to be examined simultaneously as each has a different unit of measure. Most avoided impacts occur in the categories of EP, SP, and GWP. This can be attributed to the resource savings involved with reusing structural elements. Scenario 2a avoided 38.4 Terajoule of fossil fuel consumption. To put this figure in perspective, it is equivalent to the average monthly natural gas consumption by the University of Calgary’s cogeneration plant for electricity as calculated from data for the period of April 2014 to March 2015. The scenario also avoided 3 389 t of CO2 eq of Global Warming Potential compared to a scenario with complete demolition followed by new construction. This amount of greenhouse gas emission is closely comparable to a quarter of the emissions attributed to the commuting of faculty and staff of the University of Calgary in 2008/2009. See Table 4 for a complete listing of avoided impacts from all impact categories for Scenario 2a relative to Scenario 1a. Larger values of avoided impact in Table 4 implies a positive impact of structure reuse. How large it should be to justify a decision of reuse over new construction is a subject of further research as it requires a cumulative knowledge of similar studies and is subjected to local circumstances. Ozone depletion potential was the only impact category which was not greatly influenced by building reuse. Assemblies contributing to this category mostly involved windows and exterior wall assemblies which are comparable in all scenarios. If Ozone Depletion Potential is excluded, avoided impacts due to reuse of structure ranged from 20 to 41% of those potentially produced should the MLT be completely demolished and replaced by a new
construction. Considering all seven impact categories, average and median savings were 28% and 33% respectively. As the Trombe wall requires additional material resources, the two scenarios with the Trombe wall showed environmental impacts 1–9% higher than their counterparts, the average and median of which was 4 and 3% respectively. The intermediate floors are the largest contributors for five of the seven impact categories in the complete demolition followed by new construction, Scenario 1a (Table 5). In the selective deconstruction and repurposing scenario, Scenario 2a, a similar pattern of contribution is observed where different building components contribute to varying degrees. Both scenarios have the same building component (s) as highest contributors for each impact category (shown as bold in both tables). An exception is for Acidification Potential while Intermediate Floors are the highest contributors in Scenario 1a, Windows (glazing and metal sheeting) appear as the largest contributor in Scenario 2a (see Table 6 below). Table 7 shows the environmental impact associated with the Trombe wall. The contribution from this building system is the same for both the new construction and the selective deconstruction scenarios.
4. Discussion The main purpose of the research was to get a quick estimate of the differences between a complete demolition followed by new construction and selective deconstruction of the building followed by repurposing scenarios. The EcoCalculator was preferred for this analysis as it is a simplified tool capable of giving quick results suitable for early stage design table discussions where there are few resources and requirements for detailed analysis. The results fulfill the purpose of identifying the best alternative and allow later further analysis to then focus on the impact of different individual components, materials, and designs options. Data used was limited to materials used in the different parts of the building under each scenario as read from drawings and obtained from construction documents through the Architecture unit of the Facilities Management of the University. The selective deconstruction and repurposing scenarios show 20% to 41% less impact in six out of seven environmental impact categories assessed. The highest reduction is achieved for Eutrophication Potential followed by Smog Potential at 37% reduction. Out of the six categories that showed significant difference, Human Health Criteria is the least reduction at 20% followed by Acidification Potential at 29%. Due to the close correlation between Global Warming Potential and Fossil Fuel Consumption, both show an avoided impact of 33 and 34% respectively associated with the University’s decision to go for repurposing after selective deconstruction rather than complete demolition and new construction. The role of Trombe wall is insignificant in terms of increasing the magnitude of most of the impact categories. The relatively significant increase is only seen for the Human Health Criteria at 9%. Overall despite its contribution to the impact categories, it shows no influence in changing the overall ranking of the scenarios. Comparing the outcome of this analysis with similar analysis in the literature in terms of the reduction in impacts of reuse of structure versus new construction is important even though each building is unique in different ways and it is difficult to find studies done for the same type of building in the same climatic zone. The general findings of this study are in agreement with that of a study done by Vandenbroucke, Galle, De Temmerman, Debacker, and Paduart (2015) on student residences in Belgium that concluded from a life cycle perspective the reuse and transformation of the student resi-
G. Assefa, C. Ambler / Sustainable Cities and Society 28 (2017) 146–153
151
Table 5 Percentage contribution of different building elements for the seven impact categories in Scenario 1a. Building Systems
FFC (MJ)
GWP (tonnes CO2 eq)
AP (mol H+ eq)
HHC (kg PM10 eq)
EP (g N eq)
ODP (mg CFC-11 eq)
SP (kg NOX eq)
Foundation &Footings Columns & Beams Intermediate Floors Exterior Walls Windows Roof Total
8% 25% 33% 14% 11% 9% 100%
9% 21% 37% 15% 12% 5% 100%
8% 18% 32% 18% 20% 4% 100%
6% 10% 23% 23% 33% 4% 100%
8% 36% 37% 9% 6% 4% 100%
≈0% ≈0% ≈0% 59% 31% 9% 100%
11% 17% 46% 10% 11% 5% 100%
Bold values show the highest contributing building system(s).
Fig. 1. Impact assessment results of scenarios relative to Scenario 1a.
Table 6 Percentage contribution of different building elements for the seven impact categories in Scenario 2a. Building Systems
FFC (MJ)
GWP (tonnes CO2 eq)
AP (mol H+ eq)
HHC (kg PM10 eq)
EP (g N eq)
ODP (mg CFC-11 eq)
SP (kg NOX eq)
Foundation &Footings Columns & Beams Intermediate Floors Exterior Walls Windows Roof Total
6% 18% 25% 22% 16% 13% 100%
7% 16% 28% 23% 18% 8% 100%
5% 12% 23% 25% 29% 6% 100%
4% 6% 14% 29% 41% 5% 100%
7% 30% 31% 15% 10% 7% 100%
0% 0% 0% 59% 31% 9% 100%
9% 14% 36% 15% 18% 8% 100%
Bold values show the highest contributing building system(s).
dences compared to demolition and rebuilding have a significantly lower impact. The findings are limited for the scenarios characterized in terms of the early versions of the repurposing documents. As the project is pushed up for potential provincial funding, the materials and assemblies of the repurposing project will be more detailed which is not the case for the data used in this research. The EcoCalcu-
lator does not account for the use phase in terms of operational energy use of buildings. Assumptions made in the development of the comparative scenarios may have influenced results. In Scenario 1a, it is assumed that the new building would occupy the same footprint and have the same number of floors as the currently standing library tower. In addition, it would also be based on the same foundation and structural assemblies. As the library tower
152
G. Assefa, C. Ambler / Sustainable Cities and Society 28 (2017) 146–153
Table 7 Environmental Impacts of Trombe Wall. Impact
Value
FFC (GJ) GWP (tonnes CO2eq) AP (mol H+ eq) HHC (kg pm 2.5 u eq) EP (g N eq) ODP (mg CFC −11 eq) SP (kg Nox eq)
2273 281 156 199 5596 55 171 553 23 646
was originally designed to be completed in phases to twenty-one stories (i.e. not limited to thirteen stories as in its current state) and to be loaded with library materials it is likely that the contribution of structural elements overestimate those encountered in new construction for buildings of similar size and different purpose. A single pane glass Trombe wall building assembly, as specified in the repurposing designs, was not available in the EcoCalculator. The curtain wall building assembly was used as a substitute. This may overestimate the impact of the Trombe wall as it includes a double pane system. Finally, interior walls and other building systems were omitted or could not be included due to the limits of the EcoCalculator. Again, this likely leads to an underestimation of associated environmental impacts. In particular, pre-cast concrete column coverings were detailed in the construction drawings however, a suitable substitute could not be identified. Due to the limitation associated with the tool used and the data employed, the results obtained are better interpreted in the context of capturing the relative order of magnitude performance difference in comparing selective deconstruction versus demolition and new construction. The results are limited to provision of directional outcome focusing on the material component of the building. It is therefore limited as it excludes the energy consumption during the life span of the building. The results obtained that are based on average regional and local data are not to be used as a replacement for an outcome that is based on a fully detailed life cycle assessment using specific material and energy data. Due to its objectives of getting quick results using the limited data and information available at early stage of design discussions, the study has not included uncertainty analysis. 5. Conclusion and recommendation To have an idea of the large scale implication of the reduction figures, if only 10% of the close to half a million commercial and institutional buildings in Canada can be repurposed in a second life thus avoiding the need to replace them with new buildings and thereby achieve on average the avoidance of a Global Warming Potential around 3 300 t per repurposed building as is in the case study building, this would imply preventing the emission of 165 megatonnes of CO2 equivalent to the atmosphere. This prevented emission is significantly higher than the 130 megatonnes of emission from all human activities in nine of the thirteen provinces and territories in Canada in 2013. This represents around 23% of total Canadian GHG emissions the same year. As the University of Calgary celebrates its 50 years milestone this year (2016), close to 25 of its buildings are at least 40 years old, thus approaching the end of their functional lifespan. The result from this study, though specific to the case study building, will hopefully be useful in informing discussions around the fate of many of these old buildings. The loss of these buildings will surely add to the already present need for additional learning, research, and administrative space to accommodate an active and growing university (Wondimagegnehu & Urness, 2012). However, the same build stock also presents the opportunity to achieve better envi-
ronmental and other desired benefits if handled in a holistic way. When the buildings were built four decades ago, there is perhaps no doubt that they were fit for their purpose of the time. In the decades to come, it would be imperative to consider the best ways of increasing functional spaces within the existing stock as land will be increasingly limiting in terms of expansion through new construction. Hence the question of demolition and construction or renovation and repurposing will be not only of environmental importance but also of economic and practical significance. The economic and practical aspects, not considered in this study, are related to the time it takes to turn the building site around and the resultant disruption on surrounding activities. Reuse of a building structure reduces the volume of construction waste to be removed and eliminates some of the need for site remediation before new construction. In doing these and in bypassing construction of the structure, overall construction time could be shortened. Selective deconstruction of a building may also allow sections of the building to remain operational for the duration potentially reducing the impact of deconstruction and construction on the surrounding community of users. Obviously, due to the long lifetime of buildings, there is an inherent difficulty of predicting use type changes during the course of their lifetime. However, it is prudent for designers and developers to design-in flexibility in terms of future possible changes in use of new constructions. Universities face significant challenges as they aspire to enhance their teaching and research activities while increasing their intake capacity and financing capital projects that support the expansion. At the same time, compared to other institutions, universities have better potential to account for future use change of their new buildings already at the design board. It will be important for facility development and management entities to embrace comprehensive studies that explore different options as they navigate through the development and operational aspects of buildings and non-building infrastructure. Legacy impacts should be dealt with properly alluding to local contexts and after a holistic consideration of all relevant factors comprehensively (e.g. Sfakianaki & Moutsatsou, 2015). The local context captures, among others, the role of climatic variables as repurposing buildings in a cold climate region may not, for example, be the same as those in a hot climate region. Research focusing on the trade-off between the benefit of achieving higher performance through new construction and the additional differential embodied impacts should be carried out. In line with the aforementioned limitations of the EcoCalculator and the focused scope of this research, a life cycle assessment covering both the use phase and detailed end-of-life phase based on data from advanced design documents is recommended.
Acknowledgements The authors would like to acknowledge the contribution of the Alberta Innovates – Bio Solutions for providing the funding to the Athena Chair in Life Cycle Assessment at the Faculty of Environmental Design, University of Calgary.
References AISM. (2015). EcoCalculator: overview. Accessed on December 2015 on. http:// calculatelca.com/software/ecocalculator/overview/ Al-Hussein, M., Manrique, J. D., & Mah, D. (2009). North Ridge CO2 analysis report: Comparison between modular and on-site construction. Canada: University of Alberta. AutoDesk. (2015). Congress members look at the reinventing existing buildings.. Accessed on January 2016 at. http://sustainability.autodesk.com/blog/ reinventing-existing-buildings-nbi/ Bullen, P. A., & Love, P. E. D. (2010). The rhetoric of adaptive reuse or reality of demolition: Views from the field. Cities, 27(4), 215–224.
G. Assefa, C. Ambler / Sustainable Cities and Society 28 (2017) 146–153 Bullen, P. A. (2007). Adaptive reuse and sustainability of commercial buildings. Facilities, 25(1/2), 20–31. Chau, C. K., Leung, T. M., & Ng, W. Y. (2015). A review on life cycle assessment, life cycle energy assessment and life cycle carbon emissions assessment on buildings. Applied Energy, Vol. 143(No. C), 395–413. Conejos, S., Langston, C., & Smith, J. (2015). Enhancing sustainability through designing for adaptive reuse from the outset: A comparison of adaptSTAR and Adaptive Reuse Potential (ARP) models. Facilities, 33(9/10), 531–552. Dadhich, P., Genovese, A., Kumar, N., & Acquaye, A. (2014). Developing sustainable supply chains in the UK construction industry: A case study. International Journal of Production Economics, 164(June), 271–284. Dodoo, A., Gustavsson, L., & Sathre, R. (2009). Carbon implications of end-of-life management of building materials. Conservation & Recycling, 53(5), 276–286. Esa, M. R., Halog, A., & Rigamonti, L. (2016). Developing strategies for managing construction and demolition wastes in Malaysia based on the concept of circular economy. Journal of Material Cycles and Waste Management, 1–11. Gao, W., Ariyama, T., Ojima, T., & Meier, A. (2001). Energy impacts of recycling disassembly material in residential buildings. Energy & Buildings, 33(6), 553–562. Gursel, I. (2010). CLIP: Computational support for lifecycle integral building performance assessment. Accessed on January 2016 at. https://toi.bk.tudelft.nl/ designInformatics/index.php/phd-research/clip/ ISEDC. (2015). Corporate social responsibility: SME sustainability roadmap. Innovation, Science and Economic Development Canada (ISEDC).. Accessed on January 29, 2016 at. https://www.ic.gc.ca/eic/site/csr-rse.nsf/eng/rs00585.html Jagarajan, R., Abdullah, M. N., Asmoni, M., Mei, J. L. Y., Misnan, M. S., Jaafar, M. N., et al. (2015). A review on critical success factors of sustainable retrofitting implementation. Jurnal Teknologi, 74(2). Jaillon, L., Poon, C. S., & Chiang, Y. H. (2009). Quantifying the waste reduction potential of using prefabrication in building construction in Hong Kong. Waste Management, 29, 309–320. Langston, C., Wong, F. K. W., Hui, E. C. M., & Shen, L.-Y. (2008). Strategic assessment of building adaptive reuseopportunities in Hong Kong. Building and Environment, 43(10), 1709–1718. Mata, E., Kalagasidis, A. S., & Johnsson, F. (2010). Retrofitting measures for energy savings in the Swedish residential building stock – Assessing methodology. In Thermal performance of the exterior envelopes of whole buildings XI International Conference. NRC. (2013). Survey of commercial and institutional energy use: Buildings 2009 summary report. Ottawa, Ontario, Canada: Natural Resource Canada’s (NRC) Office of Energy Efficiency. Rohn, H., Pastewski, N., Lettenmeier, M., Wiesen, K., & Bienge, K. (2014). Resource efficiency potential of selected technologies, products and strategies. Science of the Total Environment, 473, 32–35.
153
Roussat, N., Mehu, J., & Dujet, C. (2009). Indicators to assess the recovery of natural resources contained in demolition waste. Waste Management & Research, 27(2), 159–166. Scheuer, C., Keoleian, G. A., & Reppe, P. (2003). Life cycle energy and environmental performance of a new university building: Modeling challenges and design implications. Energy & Buildings, 35(10), 1049–1064. Sfakianaki, E., & Moutsatsou, K. (2015). A decision support tool for the adaptive reuse or demolition and reconstruction of existing buildings. Int. J. Environment and Sustainable Development, 14(1), 1–19. Sfakianaki, E. (2015). Resource-efficient construction: Rethinking construction towards sustainability. World Journal of Science, Technology and Sustainable Development, 12, 233–242. Smol, M., Kulczycka, J., Henclik, A., Gorazda, K., & Wzorek, Z. (2015). The possible use of sewage sludge ash (SSA) in the construction industry as a way towards a circular economy. Journal of Cleaner Production, 95, 45–54. Thormark, C. (2001). Conservation of energy and natural resources by recycling building waste. Resources, Conservation & Recycling, 33(2), 113–130. Thormark, C. (2006). The effect of material choice on the total energy need and recycling potential of a building. Building and Environment, 41(8), 1019–1026. UNEP. (2016). Sustainable buildings and climate initiative: Why buildings. united nations environment programme (UNEP).. Accessed on January 2016 at. http:// www.unep.org/sbci/AboutSBCI/Background.asp Vandenbroucke, M., Galle, W., De Temmerman, N., Debacker, W., & Paduart, A. (2015). Using life cycle assessment to inform decision-making for sustainable buildings. Buildings, 5(2), 536–559. Wang, H.-J., & Zeng, Z.-T. (2010). A multi-objective decision-making process for reuse selection of historic buildings. Expert Systems with Applications, 37(2), 1241–1249. Wondimagegnehu, G., & Urness, C. (2012). Repurposing a university library building ?life cycle implication. In Accepted for poster presentation but not presented at LCA XII conference held Tacoma. Accessed in January 15, 2016. http://lcacenter.org/lcaxii/abstracts/674.htm Yeheyis, M., Hewage, K., Alam, M. S., Eskicioglu, C., & Sadiq, R. (2013). An overview of construction and demolition waste management in canada: A lifecycle analysis approach to sustainability. Clean Technologies and Environmental Policy, 15(1), 81–91. Yung, E. H. K., & Chan, E. H. W. (2012). Implementation challenges to the adaptive reuse of heritage buildings: Towards the goals of sustainable, low carbon cities. Habitat International, 36(3), 352–361.