An integrated BIM-based framework for minimizing embodied energy during building design

Accepted Manuscript Title: An Integrated BIM-based framework for minimizing embodied energy during building design Author: Farshid Shadram Tim David Johansson Weizhuo Lu Jutta Schade Thomas Olofsson PII: DOI: Reference:

S0378-7788(16)30604-1 http://dx.doi.org/doi:10.1016/j.enbuild.2016.07.007 ENB 6838

To appear in:

ENB

Received date: Revised date: Accepted date:

21-12-2015 1-6-2016 5-7-2016

Please cite this article as: Farshid Shadram, Tim David Johansson, Weizhuo Lu, Jutta Schade, Thomas Olofsson, An Integrated BIM-based framework for minimizing embodied energy during building design, Energy and Buildings http://dx.doi.org/10.1016/j.enbuild.2016.07.007 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

An Integrated BIM-based framework for minimizing embodied energy during building design

Shadram

Corresponding (first) author

PhD scholar (MSc)

Luleå University of Technology

Department of Civil, Environmental and Natural Resources Engineering

[email protected]

(+46) 920 493039

Tim

David

Johansson

Second author

PhD scholar (MSc, Lic.Eng)

Luleå University of Technology

Department of Civil, Environmental and Natural Resources Engineering

[email protected]

(+46) 920 493057

Weizhuo

Lu

Third author

Senior lecturer (Ph.D.)

Luleå university of technology

Department of Civil, Environmental and Natural Resources Engineering

[email protected]

(+46) 920 492866

Jutta

Schade

Forth author

Associate senior lecturer (Ph.D.)

Luleå University of technology

Department of Civil, Environmental and Natural Resources Engineering

[email protected]

(+46) 920 492571

Thomas

Olofsson

Fifth author

Chair professor

Luleå university of technology

Department of Civil, Environmental and Natural Resources Engineering

[email protected]

(+46) 920 493662

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Highlights:

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 A framework is proposed for assessing the embodied energy during the design stage

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 Assessment covers the impact of materials supply chain based on the suppliers’ EPD

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 ETL technology is integrated into the BIM process to facilitate the assessment

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 A prototype of the proposed framework is developed.

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 The prototype is finally used to test the framework’s applicability in a case study

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Abstract

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Assessment of the embodied energy associated with the production and transportation of materials

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during the design phase of building provides great potential to profoundly affect the building’s

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energy use and sustainability performance. While Building Information Modeling (BIM) gives

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opportunities to incorporate sustainability performance indicators in the building design process, it

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lacks interoperability with the conventional Life Cycle Assessment (LCA) tools used to analyse the

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environmental footprints of materials in building design. Additionally, many LCA tools use databases

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based on industry-average values and thus cannot account for differences in the embodied impacts

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of specific materials from individual suppliers. To address these issues, this paper presents a

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framework that supports design decisions and enables assessment of the embodied energy

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associated with building materials supply chain based on suppliers’ Environmental Product

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Declarations (EPDs). The framework also integrates Extract Transform Load (ETL) technology into the

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BIM to ensure BIM-LCA interoperability, enabling an automated or semi-automated assessment

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process. The applicability of the framework is tested by developing a prototype and using it in a case

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study, which shows that a building’s energy use and carbon footprint can be significantly reduced

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during the design phase by accounting the impact of individual material in the supply chain.

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Keywords

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

Embodied Energy

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

Environmental Product Declaration

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

Building Information Modeling

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

Extract Transform Load

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

Interoperability

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

Supply chain

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1. Introduction

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Considerable efforts have been made to reduce buildings’ operational energy use over the last

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decades while little attention has been paid to reducing the embodied energy use, i.e. the energy

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consumed during the off-site production and transportation of building materials and components,

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the erection of the building on-site, and any refurbishment activities that may be required [1].

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Several studies have emphasized the significance of the embodied energy [2,3] as it may account for

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up to 60% of the building’s total energy use [4,5]. It has also been reported that a significant fraction

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of a building’s energy use is attributable to the embodied energy associated with off-site production

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of building materials and components (i.e. “cradle-to-gate”) and the

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materials and components to the construction site (i.e. “gate-to-site”) [6,7, 8, 9]. Ding [6] claims that

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the off-site production of building materials and components is responsible for approximately 75% of

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the total embodied energy. A recent study on a low-energy building located in Stockholm, Sweden,

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indicated that the embodied energy would be comparable to the operational energy given an

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expected lifespan of 50 years, and that 87% of the embodied energy and GHG emissions would be

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due to the off-site production and transportation of the building materials and components to the

transportation of these

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construction site [7]. Overall, the available data indicate that the building material supply chain (i.e.

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production and transportation) contributes significantly to both the embodied energy and the total

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energy use, and should therefore be considered during the design and pre-construction phase when

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there is great scope for reducing the embodied energy.

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1.1. Life Cycle Assessment and Environmental Product Declaration

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Life Cycle Assessment (LCA) tools are the main methods used during the building design and pre-

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construction phase for evaluation and reduction of the embodied energy associated with material

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supply chain. Nevertheless, the Life-cycle Inventory (LCI) databases used by these LCA tools are often

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based on industry-average values and don’t account for differences caused in the embodied impacts

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of specific materials from individual suppliers [9,10,11]. The industry-average based databases may

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not provide accurate information on the impact of material sourced from a specific supplier given the

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fact that the energy supply, the manufacturing processes and mechanisms used to produce a specific

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material can vary substantially between manufacturers and factories. Dixit et al. [8] claim that

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current embodied energy databases are generally inaccurate and of variable quality because

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manufacturers use inconsistent methodologies to determine the embodied energy of their materials.

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One means to overcome this obstacle and get comparable data is the use of verified product-specific

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data in the form of Environmental Product Declaration (EPD). EPDs are defined as type III

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declarations under the ISO 14020:2000 standard [12], and provide detailed process-based LCA data

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for a specific product which is verified by a third party and determined based on a consistent

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methodology (Product Category Rule) which makes the result of the LCA comparable [13]. Moncaster

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and Song [14] claim that existing LCI databases primarily contain industry-average values, and

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express hope that the upcoming standardization of EPDs will lead to all manufacturers providing

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detailed and specific information on their products’ embodied energy and environmental impacts.

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Because the number of available EPDs is increasing and EPDs contain verified product-specific data

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on the embodied energy and environmental performance of specific materials from individual

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suppliers, this research recommend the use of EPDs as a consistent data source for assessing

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embodied energy and associated environmental impacts.

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1.2. Building Information Modeling and Life Cycle Assessment

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Building Information Modelling (BIM) is defined as the process of generating, storing, managing,

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exchanging, and sharing building information in an interoperable and reusable way [15]. BIM has

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become an applicable platform in the design and pre-construction phase of the building as it enables

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the sharing of multidisciplinary information in a common environment [16]. The information sharing

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capabilities of BIM can also be useful when assessing sustainability issues and making related

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decisions during the design stage [17, 18]. Azhar [19] claims that BIM-based sustainability analyses

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achieve ‘some-to-significant’ time and cost savings compared to the traditional methods. Kriegel and

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Nies [20] have listed ways in which BIM-based processes can facilitate sustainable design. Notably,

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these include promoting the selection of sustainable materials, reducing material consumption, and

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increasing the use of recycled materials. Despite the clear sustainability advantages of BIM methods,

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existing BIM software lacks interoperability with conventional Life Cycle Assessment (LCA) tools

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which are the main means for assessment of the embodied energy [21, 22]. Therefore, significant

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time and effort is required to extract and modify exported data from the BIM software to match the

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input format of these LCA tools [23,24]. This process also increases the risk of mistakes,

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misunderstandings and errors due to the manual re-entry of the project information into the LCA

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tools and hinders the integration of LCA into model-based BIM design processes. As a result,

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embodied energy assessments are often performed only after the design has been developed at a

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relatively detailed level rather than at real-time for supporting environmental decisions. The

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integration of BIM with the LCA to assess the embodied energy has also got limited attention among

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the scholars. For instance, Wang et al. [25] used Autodesk Ecotect in the Revit to facilitate

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assessment of planned buildings’ operational energy; the other components of the LCA were

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performed using a combination of external analytical tools and databases. Basbagill et al. [26]

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proposed a method for using LCA, BIM and sensitivity analysis to reduce embodied environmental

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impacts during design phase decision-making. Ajayi et al. [27] carried out a BIM-enhanced LCA

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methodology through evaluation of a case study. Kulahcioglu et al. [28] presented a prototype that

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integrates BIM with LCA and allows for the interactive analysis of a 3D building model with its

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environmental impacts. Azhar et al. [29] and Barnes and Castro-Lacouture [30] investigated the

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scope for achieving direct and indirect credit- and prerequisite savings by incorporating BIM data into

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the LEED rating certification system. Wong and Kuan [31] investigated the potential for using BIM

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data to facilitate the Hong Kong BEAM Plus certification process. Similarly, Grandhi and Jupp [32]

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studied the applicability of BIM tools for Australian green star building certification. Nevertheless, the

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major intention of these studies was to either provide new methods for the use of existing LCA tools

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along with BIM or integrate BIM with the conventional LCA tools which are mainly incapable to

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account for differences caused in the embodied impacts of specific materials from individual

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suppliers. Thereby, the use of verified product-specific data (such as EPDs) as a consistent source for

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the LCA and incorporating it to a BIM-based design process is overlooked in these conducted studies.

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1.3. Extract, Transform and Load technology

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Extract, transform and load (ETL) technologies have been used in other disciplines to overcome

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interoperability issues and manage large data sets containing information from multiple sources that

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may be recorded in different formats and using different data models [33,34]. ETL tools are generally

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used to establish repeatable processes to extract data from multiple heterogeneous data sources,

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transform the extracted data into some consistent format or structure, and finally load the

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transformed data back into a database or target application. The transformation steps include a

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variety of cleansing activities and processing by filters, sorters, groupers, and so on, all of which are

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organized into a workflow [35]. Cerovsek [36] claims that ETL tools are suitable for integrating

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different data models. As such, they could be useful in solving the interoperability problems of the

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AEC industry that were identified by Grilo and Jardim-Goncalves [37] and Tegtmeier et al. [38].

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Spatial ETL tools can integrate BIM data, information from Geographical Information System (GIS),

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performance data, and data from web services to create a seamless information flow to support

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urban planning and the design and construction of the built environment [36,39,40]. However, the

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use of ETL in the context of BIM has not been explored extensively. Isikdag [41] created a BIM-

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oriented model for indoor navigation and used spatial ETL software to validate the model’s

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interoperability with commonly used GIS file formats. Carrión et al. [42] used spatial ETL to

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automatically create a virtual 3D city model that was used in conjunction with measured data to

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estimate the energy use of buildings in a small test area in Berlin. Johansson et al. [43] adopted a

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similar approach to establish a full scale 3D city model that was used to predict the operational

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energy use of buildings served by a district heating facility.

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1.4. Research gap and research objective

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Previous research on the applicability of BIM in sustainable design processes has paid little attention

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to assessing the embodied energy based on the material EPDs as part of an integrated BIM-based

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design process. In addition, the potential of ETL technologies to automate information exchange and

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overcome some of the interoperability problems between BIM and LCA needs further investigation.

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Because there is considerable scope for reducing the embodied energy of buildings (and thus their

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total lifecycle energy consumption) by making appropriate choices during the design phase, the

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possibility to integrate analyses of embodied impacts into BIM-driven design processes should be

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investigated. The aim of this work is therefore to develop a framework that will enable assessment of

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the embodied energy arising from the materials supply chain (i.e. “cradle-to-site” embodied energy)

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in the building design stage. The assessment is based on the materials’ EPDs rather than industry-

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average databases in order to ensure that the framework can consistently compare how different

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materials and components will affect the embodied energy of the building. A long term goal is for

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this framework to serve as a platform to support the development of an automated or semi-

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automated process for straightforwardly assessing a building’s embodied energy during the building

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design process. To this end, three key objectives were identified:

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• To highlight the processes required to facilitate the use of EPDs when evaluating the embodied

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energy.

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• To incorporate the embodied energy assessment procedure into an integrated BIM-based design

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process.

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• To test the potential of ETL technologies to facilitate automated information exchange.

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The proposed framework is then implemented in a prototype which is applied in a case study to test

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the framework’s applicability in mitigating the embodied energy use in the design phase.

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The paper is structured as follows: Section 2 presents the research method, including the proposed

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framework and the developed prototype. In the section 3, the applied case study along with its

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results and a discussion of the results are illustrated. Finally, the last section concludes the

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framework’s applicability and highlights limitations and the areas where further development is

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required.

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2. Method

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The method in this research includes (1) proposed framework (2) developed prototype. The

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proposed framework presents the conceptual distinctions, required processes and the information

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flow for the assessment of embodied energy associated with building materials supply chain, while

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the developed prototype implements the framework and serves as a tool for testing the applicability

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of the framework in the case study.

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2.1. Proposed framework

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A framework for evaluating the embodied energy associated with the supply chain of materials is

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proposed. The framework is repeatable in nature and supports decision-making relating to

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alternative designs and selection of material and components from an environmental perspective

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through design iteration (see figure 1).

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Figure 1. The proposed framework for assessment of the “cradle-to-site” embodied impact.

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The framework features four main modules that are used in each assessment. These modules are

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described below:

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1. Database

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The core module of the framework is a generic database that contains all of the relevant data items,

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which are organized into a set of interacting relations with no need for reorganization during

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reassembly. Five relations within the database are used in the assessment of the embodied energy,

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each of which is discussed briefly below:

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

The EPD inventory provides data about the embodied energy and environmental

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performance of different materials and components from different suppliers. At present,

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most of the EPDs for materials and components are drawn from various open access

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databases on the internet. However, the Functional Units (FUs) used in these EPDs are not

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standardized and may therefore differ significantly for materials or components of the same

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type that have been sourced from different suppliers. For example, the FU for a given type of

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insulation may be 0.1 m3 from one supplier and 0.035 m3 from another supplier. Therefore,

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EPDs are collected from these open access databases and stored in a relation to establish an

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EPD inventory that can be used as a fundamental tool for assessing the embodied energy. In

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addition, the environmental performance data and embodied energy associated with the

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EPDs must be normalized so that each example of a given material or component uses the

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same FU. While the main purpose with this framework is to facilitate assessments of the

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embodied energy, the EPDs also include information on the embodied carbon and other

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environmental outcomes associated with the production of the materials from cradle to

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gate, so the framework could potentially be extended to evaluate these environmental

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consequences as well.

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

The Component Library (CL) contains predefined component recipes, i.e. lists of the

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constituent materials for each component of the building and the quantities in which they

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are used.

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

The Building Part Library (BPL) is a CL on a larger scale: it contains “recipes” for predefined

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building parts, i.e. lists of the components required to construct each part. Each building part

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recipe can thus be regarded as a collection of predefined component recipes, and specifies

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the quantity of individual components required to build the part in question.

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Figure 2 illustrates the data recorded in the CL, BPL and the EPD inventory.

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Figure 2. An illustration of the kinds of data recorded in the BPL, CL and EPD inventory of the

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database.

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As shown in the figure 2, the database is dominated by Kind_of structures. The part_of structures

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represent a set of classes in which each class is a common denominator for a group of either building

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parts, components or EPDs. Conversely, the Kind-of structure represents different kinds of classes,

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which are the main constituents of the stored relations in the database.

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

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Fuel provides information concerning the embodied energy and environmental performance of different fuel types.



Transportation modality (TM) provides data on various transportation modes including their

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maximum load- and volume capacities and the fuel consumption of each transport mode per

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distance.

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2. Integrated BIM & Embodied design process

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The proposed framework consists of an integrated BIM design process in which the composition of

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the embodied recipes and the building design can be developed and implemented in parallel with

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each other. The term “embodied recipe” in this framework is defined as the embodied energy,

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embodied carbon and/or environmental impacts of an object (per 1 FU). An object represents either

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a predefined building part or a predefined component, which can be chosen from the BPL or CL of

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the database, respectively. The embodied recipes are defined by means of three subprocesses, each

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of which starts with the selection of a building part or component object from the database. The

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selected object can then be substituted and modified to accurately represent the actual building part

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and/or component associated with the design. For example, if a predefined building part in the BPL

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has parameters differing from the actual building part, its components can be replaced with new

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components using the CL in the database. Once the objects have been satisfactorily modified, the

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user can define suppliers and attribute EPDs to either their constituent materials or components. The

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outcome of these three subprocesses is the creation of a set of embodied recipes that specify the

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“cradle-to-gate” embodied energy (per 1 FU) for each of the objects. These embodied recipes can be

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stored and identified with unique codes, which are subsequently utilized to classify the design

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object’s attribute (components and building parts) in the BIM tool. This classification will facilitate

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the extraction of the quantities associated with the embodied recipes from the BIM tool.

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3. Quantity take-off and tracking transportation distances

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In the proposed framework, the Extract Transform Load (ETL) technology is used to extract both the

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composed embodied recipes and the corresponding quantities from the BIM tool. However, the

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quantities from the BIM tool can also be extracted using internal Quantity Take-Off (QTO) functions

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in the BIM software or other external QTO tools.

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The distance between the suppliers and the construction site is also tracked automatically by an ETL

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process. Initially, the ETL extracts the data on the applied EPDs (or suppliers) as well as the quantities

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and volumes from the BIM model and the newly composed embodied recipes. Once the relevant

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EPDs have been identified, the suppliers’ manufacturing locations (which are stored in the EPD

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inventory) and the location of the construction site are used to query an external map web service

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application (API). The map web service API calculates the transportation distances from each supplier

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to the construction site, and cycles recursively through the ETL process to extract estimated

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transportation distances for the entire supply chain from the map web service API. Finally, the

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calculated distances and the quantities and volumes for each applied EPD are used to assess the

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gate-to-site embodied energy.

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4. Assessment of the “cradle-to-site” embodied energy

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After the quantities from the BIM tool and the composed embodied recipes have been extracted

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through the ETL process, the cradle-to-gate embodied energy can be estimated simply by linking the

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extracted quantities to the associated embodied recipes.

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The required number of transportations from each supplier to the construction site is estimated

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using data concerning the materials’ volume capacity utilization factor (VCUF), which is obtainable

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from the EPD inventory, as well as the total quantity and volume of each material and the maximum

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load and volume capacity of the selected transportation mode. The contribution of transportation to

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the embodied energy can then be assessed from the required number of transportations, the

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distance between each supplier and the construction site, the fuel consumption of the chosen

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transport mode, and the embodied energy and environmental performance of the applied fuel.

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2.2. Developed prototype

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In order to implement the framework and test its applicability in reducing the energy use in the

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design process, a prototype is developed and used to assess the embodied energy in the applied case

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study. The prototype of the proposed framework uses Autodesk Revit as building design tool, the

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Feature Manipulation Engine (FME) as the spatial ETL tool, Google Maps (GM) API as the map web

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service API and Power Pivot for implementing the rest parts of the proposed framework (i.e.

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“database”, “compose of the embodied recipes” and “assessment of the “cradle-to-site” embodied

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energy”), see figure 3. Power Pivot is an add-in to Microsoft Excel which enables to set up database

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models by creating a connection to different data sources (such as Microsoft SQL, Excel files etc) and

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also provides analytical capabilities by using data analysis expression (DAX) language [44].

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Figure 3. An overview of the developed prototype of the proposed framework

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Hereupon, due to the prominent capabilities of Power Pivot in setting up relational databases and

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performing data analysis, two interfaces; database- and assessment interface, are developed in the

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Power Pivot. The database interface in the Power Pivot (see figure 3) represents the generic

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database (module 1) of the proposed framework and as illustrated earlier, it includes 5 relations: EPD

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inventory, CL, BPL, TM and fuel. The assessment interface in the Power Pivot instantiates “compose

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of the embodied recipes” (part of module 2) and “assessment of the cradle-to-site embodied energy”

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(module 4) of the proposed framework. These two interfaces are linked to each other with the

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relations being defined using primary- and foreign keys. The dashed arrows in figure 3 represent the

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relationships between these interfaces. Hence, the boxes in which the dashed arrowheads refer to,

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are the primary relations and the boxes that the dashed arrows exit from, represent the foreign

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relations. These relationships enable the user to have access to the primary sources of data and

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simply select the required data at any stage during the evaluation. For instance, the relationships

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involved for “compose of the embodied recipes”, enable the user to simply select an object

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(predefined building part- or predefined component recipe) either from BPL- or CL relations and

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substitute and modify the objects by having access to different recipes stored in these two relations.

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Once the object is satisfactorily modified, in order to “compose the embodied recipe”, the user

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defines suppliers and attribute EPDs to either their constituent materials or components (the

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relationship between the EPD inventory and CL enables execution of this task). For a detailed

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overview of the developed interfaces in the Power Pivot see Appendix A: Power Pivot.

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In order to assess the cradle-to-site embodied energy in the Power Pivot, two external data are

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required: (1) the quantity of each object from the Autodesk Revit (BIM tool), (2) The transportation

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distances between the suppliers to the construction-site (see module 3 of the proposed framework).

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In this prototype, each of which data is processed and managed in an automatic manner into the

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Power Pivot by use of the spatial ETL tool FME (the solid arrows in figure 3 represent these two data

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flow processes). Thereby, 2 workflows/algorithms are developed in FME, see figure 4 and 5.

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Figure 4. The developed workflow in the FME for extraction of the quantities from BIM tool

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The 1st workflow (see figure 4) is used to automatically extract the quantities of the objects from the

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Autodesk Revit, transform and load the extracted quantities in the proper format to the Power Pivot

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application. The steps involved in the development of the 1st workflow are as follows:

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1. Quantity take-off object filtering: The BIM objects are first filtered by the “quantity take-off

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object filtering” algorithm based on feature type (e.g. wall or door). This filtering enables the

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selection of design objects under consideration.

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2. ATTRIBUTE MANAGEMENT: In this step the unnecessary attributes of the selected BIM object’s are removed. 3. AGGREGATION: the attributes are aggregated by object type and the quantified objects are then exported to the Power Pivot.

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The 2nd workflow is developed in FME to track the transportation distances between suppliers and

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construction-site in an automatic manner. This workflow consists of two sub-processes (see figure 5)

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in which first FME extracts the address of each supplier from the Power Pivot, and the construction

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site’s location from the BIM tool (the construction site’s location could also be entered manually).

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These data were then transformed and used as inputs to the GM API, enabling it to track and

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calculate the transportation distances from each supplier to the construction site. Afterwards, in the

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second sub-process, the FME in a recursive cycle extracts the estimated distances from the GM API,

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transfer and finally load in a proper format into the Power Pivot for the final assessment.

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Figure 5. The developed workflow in FME for tracking the transportation distances.

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As Shown in figure 5, the steps involved in the development of the 2nd workflow are as follows:

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1. GEOCODING: The suppliers address attribute is sent to the Googe Maps API in order to get a

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geocoded point of the supplier’s location. 2. VECTOR TO TABULAR: The geocoded point is transformed into a database table row that contains the supplier’s latitude and longitude attribute.

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3. UNCONDITIONAL JOIN: Each supplier’s location is unconditionally joined with the construction

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site location imported from the BIM model. This creates a data set containing both the suppliers-

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and the construction site longitudes and latitudes.

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4. HTTP CALLER: is used to call the Google Maps API homepage with the construction site and suppliers’ locations, the transportation modality and the license key. 5. XML TO TABULAR: Google Map returns an XML file with several waypoints which is transformed into a suitable database structure. 6. ATTRIBUTE MANAGEMENT: The waypoint attributes are renamed, cleaned and the unnecessary attributes are removed. 7. AGGREGATION: The waypoints distance-and time data are added, grouped and finally loaded into the Power Pivot for the final assessment.

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For a detailed overview of the developed workflows in the FME, see Appendix B: Developed

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workflows.

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3. Applied case study

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The prototype is applied in a case study to test the proposed framework’s applicability as a decision

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support tool for mitigating the embodied energy from the supply chain in the design development of

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a building. A recently built low-energy house in the form of semi-detached dwelling consisting of two

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duplex apartments with a habitable surface area of 140 m2 is used in this test. The dwelling is located

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in the municipality of Kiruna in northern Sweden, which has a subarctic climate (see figure 6). The

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main active energy system in each apartment is an air handling unit that is equipped with an air to air

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heat exchanger with 89% efficiency and a heating coil connected to the district heating grids. In

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addition to the air handling units, photovoltaic cells are located on the wall façades facing south and

347

east to directly convert sunlight into electricity.

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Figure 6. The semi-detached built dwelling and its location.

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The design of the dwelling’s external wall was utilized as the test case (see figure 7). The wall’s

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thickness was held constant and a range of different scenarios based on the use of alternative

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insulation materials from different suppliers were evaluated to assess the proposed framework’s

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applicability.

354 355

Figure 7. A 2D cross-sectional drawing of the main wall structure in the built dwelling.

356

As shown in Figure 7, the main wall of the built dwelling consists of 2 isodiametric layers of

357

polyisocyanurate (PIR) insulation, each of which is 70 mm thick. The thermal conductivity of the PIR

358

insulation is lower than that of conventional insulation materials such as mineral wool (MW).

359

Consequently, PIR insulation performs better than these insulation materials in terms of operational

360

energy. However, its content of embodied energy is higher than conventional insulation materials.

361

Therefore, the aim of the case study was to compare the total change in embodied and operational

362

energy caused by replacing the PIR insulation layers of the dwelling’s wall with alternative insulation

363

materials from different suppliers. Hypothetical suppliers were defined for each material considered

364

in the case and the insulation materials and suppliers were selected to cover all the applicable,

365

verified and registered insulations in the three core- and International EPD databases (Norwegian

366

EPD foundation [45], the international EPD system [46] and German institute of construction and

367

environment (IBU) [47]). In order to create a logical hypothesis and reasonable evaluation, only the

368

European manufactured insulations which were applicable in the timber frame walls were selected

369

and thus, insulation materials such as expanded-and extruded polystyrene insulations (EPS and XPS)

370

as well as vacuum insulation panels (VIP) were not considered as alternative insulations since these

371

materials are not applicable in the timber frame walls.

372

In total, nineteen scenarios were evaluated. The base or reference scenario is the case in which the

373

wall is constructed with the PIR that was actually used. The first and second scenarios assume the

374

use of PIR insulation from different suppliers to that for the base scenario. In the other seventeen

375

scenarios, the 2 isodiametric PIR insulation layers are replaced with either glass wool (GW) or rock

376

wool (RW) from various suppliers. Table 1 provides details of the nineteen alternative scenarios and

377

the base case. Since the suppliers of the other constituent materials of the external wall were the

378

same in all scenarios, they are not discussed further.

379

Table 1. The base scenario and the hypothetical scenarios considered in the case study Scenario

Material

Manufacturing location

Thermal conductivity (W/m.K)

Base (Initial material)

PIR

Belgium (Desselgem)

0.023

1st

PIR

Belgium (Brussels)

0.023

2nd

PIR

Germany (Stuttgart)

0.026

3rd

GW

Belgium (Vise)

0.035

4th

GW

Belgium (Vise)

0.032

5th

GW

Belgium (Vise)

0.032

6th

GW

Germany (Ludwigshafen)

0.035

7th

GW

Czech republic (Krupka)

0.035

8th

GW

Denmark (Vamdrup)

0.037

9th

GW

Norway (Askim)

0.035

10th

GW

Sweden (Billesholm)

0.035

11th

RW

Belgium (Vise)

0.037

12th

RW

Belgium (Vise)

0.035

13th

RW

Belgium (Vise)

0.035

14th

RW

Germany (Sankt egidien)

0.035

15th

RW

Germany (Gladbeck)

0.035

16th

RW

Slovenia (Skofja Loka)

0.039

17th

RW

Slovenia (Skofja Loka)

0.035

18th

RW

Norway (Trondheim)

0.037

19th

RW

Sweden (Hällekis)

0.035

380 381

3.1. Assessment of the embodied- and operational energy

382

The embodied energy associated with the case study was assessed by utilizing the developed

383

prototype illustrated earlier in subsection 2.2. The differences in operational energy use between

384

each scenario were investigated by using a dynamic multi-zone simulation model implemented in IDA

385

ICE [48]. To make the results comparable, all of the scenarios were simulated in an identical

386

environment using the properties of the actual built dwelling (i.e. thermal bridges, ground

387

properties, infiltration, pressure coefficient, average climate data, HVAC system, etc.). Conversion

388

factors were used to convert the estimated delivered energy (secondary energy) for each scenario

389

into operational energy (non-renewable primary energy) and associated GHG emissions. These

390

factors were provided by the Tekniska Verken in Kiruna AB (the company in charge of Kiruna’s district

391

heating plants). The reported environmental analysis for district heating production by Tekniska

392

Verken in 2014 declares a primary energy factor of 26% and approximately 120.35 g CO 2 equivalent

393

emissions for the production of 1 kWh of heat; this figure includes all emissions from production,

394

combustion and transportation. The contribution of the non-renewable primary energy (NRPE) to the

395

primary energy associated with the district heating production is also estimated to be 26% (see Table

396

2).

397

Table 2. Distribution of energy sources for heat generation supplied to Kiruna’s district heating plant,

398

and the corresponding NRPE contributions to the primary energy during 2014 Supplied energy

Proportion of the

NRPE Conversion Factor

Contribution of the supplied

source

total supplied energy

energy source to the total

source (%)

NRPE (%)

Oil

2.2

1

2.2

Household hazardous

39.7

0.31a

12.3

Industrial waste

21.4

0.38a

8.1

Wood chips

12.6

0

0

Peat

2

1

2

Electricity

2.7

0.53b

1.4

Waste heat from

12.5

0

0

industry Flue gas condensation

6.9

0

0

SUM

100

---

26

waste

399 400

a Swedish Environmental Protection Agency. Hänvisningsvärden som publicerats av naturvårdsverket enligt artikel 31.1 c i kommissionens förordning (EU)

401

601/2012 [reference values published by the swedish environmental protection agency under article 31.1 c commission regulation (EU) 601/2012].

402

http://www.naturvardsverket.se/upload/miljoarbete-i-samhallet/miljoarbete-i-sverige/utslappshandel/referensbibliotek/hanvisningsvarden-utslappshandel-

403

publicerade-konstanter-enl-art-31-punkt-1c-121108.pdf. Updated 2012. Accessed December/5, 2015

404

b Vattenfall. [Elens ursprung och miljöpåverkan [origin of electricity and its environmental impact]. http://www.vattenfall.se/sv/elens-ursprung.htm. Updated

405

2014. Accessed December/5, 2015

406

3.2. Result

407

All of the scenarios were assessed on the basis of the parameters presented in Table 3.

408

Table 3. Parameters considered when assessing the scenarios Parameter

Value

Waste factor

6% for all the insulation materials

Fuel type, consumption of vehicle and

Diesel, 38 liters consumption for 100 km, truck (32 ton)

the vehicle used for the road transport

Embodied energy of diesel = 32.5a (MJ/L) CO2 emission from diesel consumption = 2.62b (kg/L) Diesel, coastal shipping

Fuel type and impact for coastal Average embodied energy = 0.27c (MJ/t.km) transport Average CO2 emission = 0.061d (kgCO2e/t.km) Capacity utilization (including empty

100 % of the capacity in volume

return)

30 % in the empty return

Volume capacity utilization factor for all 1 insulating materials Lifespan of the dwelling

50 years

409 410

a O'Brien A, Carley S, Loveridge F, Hsu Y. Innovative use of clay backfill at the new wembley stadium. 2007

411

b Ecoscore. How to calculate CO emission level from fuel consumption? http://www.ecoscore.be/en/how-calculate-co2-emission-level-fuel-consumption.

412

Updated 2015. Accessed November/1, 2015

413

c Embodied energy of building materials. https://upstyleindustries.files.wordpress.com/2014/08/materiallife-embodied-energy-of-building-materials.pdf.

414

Updated 2013. Accessed November/1, 2015

415

d European Environmental Agency. Energy efficiency and specific CO emissions. http://www.eea.europa.eu/data-and-maps/indicators/energy-efficiency-and-

416

specific-co2-emissions/energy-efficiency-and-specific-co2-5. Published 24 Jan 2013. Updated 2015. Accessed November/1, 2015

417

2

2

418

From an energy perspective, the “cradle-to-gate” assessments indicated that using GW or RW as the

419

insulating material rather than PIR significantly reduced the building’s embodied energy (see Figure

420

8). The first and second scenarios (in which the actual PIR insulation was replaced with alternative

421

PIR materials sourced from Belgium and Germany) provided only a minor reduction in embodied

422

energy (5.2 and 4.1 GJ, respectively); the highest reduction (71.5 GJ) was achieved in the 8 th and 18th

423

scenarios, in which the PIR insulation was replaced respectively with glass wool from Denmark and

424

rock wool from Norway. The “gate-to-site” embodied energy increased in the 2nd, 16th and 17th

425

scenarios due to the longer transportation distances in these cases, which had a counterproductive

426

effect on the total embodied energy relative to the other considered scenarios. Although the RW in

427

the 18th scenario was manufactured in Norway, the “gate-to-site” embodied energy for this scenario

428

was significantly lower than in other cases due to the short distance between the site of manufacture

429

and the construction site. In all scenarios except the first one, the operational energy increased in

430

parallel with the thermal conductivity of the insulation materials. The smallest increase relative to

431

the base case occurred in the 2nd scenario (PIR insulation from Germany) and the largest in the 16th

432

scenario. When considering the total energy change over 50 years, the greatest savings were

433

achieved under the 18th and 19th scenarios, which yielded reductions of 93.3 and 85.1 GJ relative to

434

the base scenario, respectively.

435 436

Figure 8. Results of the energy assessments. Minus signs indicate energy savings or reductions while

437

plus signs indicate increased energy use relative to the base case.

438

From a global warming perspective, the embodied carbon associated with the “cradle-to-gate” and

439

“gate-to-site” phases exhibited a broadly similar trend to the embodied energy, yielding a “modest-

440

to-significant” reduction of the building’s carbon footprint (see Figure 9). The reduction of “cradle-to-

441

site” embodied carbon was largest for the two materials/suppliers from Norway (i.e. 9th and 18th

442

scenarios), both of which reduced CO2 emissions by approximately 5 tons relative to the base. In all

443

scenarios, the carbon footprint associated with the operational phase increased more markedly than

444

the non-renewable operational energy use. The difference between embodied energy use and

445

embodied carbon emissions was especially pronounced for 14th, 16th and 17th scenarios. Although a

446

significant amount of life cycle energy was saved in these scenarios, the overall carbon emissions

447

actually increased, mainly due to a higher embodied carbon emission associated with the production

448

of the RW in these scenarios compared to the other RW suppliers. However, it should also be noted

449

that for the 16th scenario, the increased emissions due to the district heating during the building’s

450

operation have also a significant impact on the overall carbon emissions. In summary, the 9 th and 18th

451

scenarios achieved the greatest reductions in CO2 emissions relative to the base scenario.

452 453

Figure 9. Carbon footprint assessments. Minus signs indicate carbon savings or reductions in CO2

454

emissions while plus signs indicate increased CO2 emissions.

455

3.3. Discussion

456

Glass wool is mainly produced from recycled glass at about 700 °C while rock wool is manufactured

457

from melted stone material at a higher temperature, (~1700 °C). Consequently, the embodied energy

458

associated with the production of the rock wool is generally assumed to be higher than that for glass

459

wool [49]. However, rock wool is typically more fire resistant than glass wool due to its greater

460

melting point. As such, it may be difficult for purchasers to decide whether to priorities fire

461

resistance or the minimization of embodied energy. The results of the case study contradict the

462

general assumption that glass wool outperforms rock wool in terms of embodied energy - for

463

example, compare the results for scenarios 4 and 13 (GW and RW from Belgium), 9 and 18 (GW and

464

RW from Norway) as well as 10 and 19 (GW and RW from Sweden) in Figure 8. The results also

465

indicate that the “cradle-to-gate” embodied energy for a given type of material can vary significantly

466

depending on the supplier, as demonstrated by comparing scenarios 4 and 8 (GW from Belgium and

467

Denmark), 14 and 18 (RW from Germany and Norway) as well as 17 and 18 (RW from Slovenia and

468

Norway). Excluding the hot water demand and the household and operating electricity, the

469

difference between the “cradle-to-gate” embodied energies for these aforementioned scenarios

470

using the same kind of insulating material is equivalent to roughly 5 years of the operational energy

471

use for heating the dwelling. It was also observed that the rock wool manufactured abroad (in

472

Norway; scenario 18) performed better than locally produced materials from Sweden (scenarios 10

473

and 19) with respect to “gate-to-site” embodied energy and embodied carbon. This was mainly due

474

to a shorter gate-to-site distance in the former case. The applied energy supply system also has

475

significant effects on both the energy use and the GHG emissions associated with the dwelling’s

476

operational phase. However, the case study indicated that although the operational phase was the

477

dominant source of lifetime GHG emissions for the building, it was not so dominant with respect to

478

the total energy consumption. This was because a significant proportion of the heat generated at the

479

Kiruna’s district heating plant comes from the combustion of hazardous household and industrial

480

waste, which has a comparatively low content of non-renewable primary energy relative to the

481

amount of CO2 emitted. Overall, the total carbon footprint reduction for the 9th, 10th, 18th and 19th

482

scenarios was equivalent to more than one year of CO2 emissions during the dwelling’s operational

483

phase, excluding electricity and hot water consumption (which are estimated to account for around

484

1.5 ton equivalents of CO2 emissions annually). However, the use of green energy supply systems is

485

not only restricted to the impact of the operational phase but can also affect the material

486

production. Disregarding the variety of processes and mechanisms that can be used to produce

487

materials at the suppliers’ facilities, the use of energy from greener sources in manufacturing can

488

enable suppliers to significantly reduce the embodied impact of their products.

489

4. Conclusions

490

A framework for assessing the embodied energy in a building materials supply chain was proposed

491

and evaluated by the use of a developed prototype in a case study. Several aspects of the framework

492

made it possible to create a semi-automated process for assessing the embodied energy during the

493

design development phase of a building’s life cycle, including:

494

 The predefined recipes, which are stored in a generic database and linked to the inventory of the

495

material EPDs. This facilitates the creation of embodied recipes containing the embodied energy

496

and impact of each object used in the construction of the building (or building component) of

497

interest.

498

 An integrated BIM process that incorporates the composed embodied recipes into the BIM tool by

499

classifying the BIM object’s attributes, facilitating the extraction of quantities from the BIM tool

500

and their attribution to the associated composed embodied recipes in order to enable the final

501

assessment.

502

 An automated ETL process that serves as a core for processing and integration of BIM and EPD

503

data throughout the evaluation, automating the tracking of distances between suppliers’ facilities

504

and the construction site as well as the quantity take-off from the BIM tool.

505

The framework utilizes the ETL technology to overcome the interoperability problem for managing

506

the BIM data towards sustainability analysis in order to reduce the amount of time, effort and the

507

risk of mistakes caused by the manual re-entry of the BIM data into the LCA tools. The use of ETL

508

technology to ensure BIM-LCA interoperability is therefore one of the major contributions of this

509

paper as its use is overlooked to a major extent in the context of BIM and also among the prior BIM-

510

LCA approaches that aimed to ensure BIM-LCA interoperability. The framework also uses EPDs as

511

sources of verified product-specific data that provide consistent information on the environmental

512

performance of specific materials from different suppliers. The use of EPDs makes it possible to

513

select materials with low embodied impacts during the design development of buildings and to use

514

environmental performance as a selection criterion during procurement in conjunction with or in

515

place of other criteria such as costs. The widespread use of this framework or related tools would

516

publicize the relative environmental costs of different materials, potentially increasing competition

517

between suppliers as well as legal and public pressure to offer more eco-efficient materials and

518

adopt green supply chain management. Moreover, the framework provides some insights into the

519

impact of transportation on embodied energy, which can be used during material selection. This is

520

important because the results of the case study clearly showed that the use of locally sourced

521

materials does not necessarily reduce embodied impacts, and that it is important to consider both

522

the distance over which materials are transported and their mode of transportation when assessing

523

their environmental impact. Overall, the proposed framework was found to be a powerful and useful

524

decision support tool for assessing and reducing the embodied energy associated with materials

525

supply chains during the design development of buildings.

526

It should be noted that at present, most EPDs stored in open access databases exist in PDF format.

527

The lack of a properly standardized format for EPDs (for example in XML and/or IFC) limits the scope

528

for automatically storing new EPDs in the database. This problem could be overcome by the universal

529

adoption of a superior standard format for EPDs or via improvements in ETL technology. Regardless,

530

the limitation created by the lack of standard format was apparent during the prototype

531

development as well as the case study evaluation: it was necessary to manually enter all information

532

from the EPD PDF-documents into the Power Pivot database which resulted that the assessment

533

process could not be fully automated. With respect to transportation, there are several parameters

534

that could potentially have important effects on the “gate-to-site” embodied energy and embodied

535

carbon, including traffic conditions, road infrastructure, the characteristics and energy efficiency of

536

the chosen transportation mode (i.e. vehicles, trains, or ships), driving behavior, and the real share of

537

empty running based on the next loading point. Many of these parameters are not accounted for in

538

the proposed framework and were thus not considered during the case study. However, the

539

framework uses a generic database that could readily be extended to enable more accurate

540

assessments of the embodied energy and GHG emissions associated with transportation if suitable

541

data were collected. For instance, information about the characteristics and energy efficiency of

542

different transportation modes (e.g. different truck and/or vessel types) could be obtained from

543

vehicle manufacturers and added to the database so that these issues could be accounted for when

544

assessing impacts due to transportation.

545

The scope for considering embodied impacts during the design phase can also be influenced by the

546

project delivery system. The framework presented herein is probably easier to implement in a

547

design-build contract system, in which a single contractor is responsible for both the design and the

548

construction process. This would make it easy for the contractor to investigate alternative materials

549

and designs in order to determine how each would affect the embodied energy. Conversely, in

550

design-bid-build project delivery systems, the design is drawn up in advance by architects and

551

engineers before a contractor is recruited. Although there appears to be less scope for investigating

552

alternative designs under such a system, the proposed framework can still be used to select more

553

environmentally friendly materials from different suppliers if the design is not affected. The

554

exploratory nature of this study, therefore requires further research to validate the findings in real

555

construction projects in order to consolidated a methodology for embodied impact assessment

556

based on the proposed framework to be applied in the construction industry. For industrial

557

applications, the prototype needs also further development in order to simplify the exchange of

558

information between the BIM and the LCA. This study doesn’t cover the embodied impact associated

559

with the on-site construction processes and neither the procurement costs. Therefore, the future

560

studies may expand the framework in order to address the embodied impact caused by construction-

561

site as well as the trade-off between cost and environmental strategies.

562

5. Acknowledgement

563

This study is part of the Alice and Attract project and authors would like to gratefully thank Formas

564

(the Swedish research council) and Vinnova (Sweden’s innovation agency) for funding these projects.

565

The authors would also like to acknowledge NCC construction company for providing the data on the

566

applied case study.

Appendix A: Power Pivot

Appendix B: Developed workflows

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