Building retrofit is considered as a vital step to achieve energy and climate goals in both Europe and Sweden. Nevertheless, retrofitting solutions based merely on reducing operational energy use can increase embodied energy use, mainly due to altering the existing trade-off between the two. Considering this trade-off is vitally important, especially for retrofitting buildings located in cold climate regions, as reduction of operational energy use to meet standards of energy-efficient buildings may require a deep retrofitting that can considerably increase the embodied energy and thus be unfavorable from a Life Cycle Energy (LCE) perspective. This article presents a case study in which multi-objective optimization was used to explore the impact of a wide range of retrofitting measures on the aforementioned trade-off for a building in Sweden located in a subarctic climatic zone. The studied building was a typical 1980s multi-family residence. The goal was to explore and compare the optimal retrofitting solution(s) for the building, aiming to achieve Swedish energy-efficient building standards (i.e. new-build and near-zero energy standards). The results of the optimization indicated that (1) use of additional insulation in walls and roof, (2) replacement of existing windows with more energy-efficient ones, and (3) change of traditional mechanical extract ventilation to heat recovery ventilation are the primary and optimal retrofitting measures to fulfill the new-build Swedish energy standard and achieve highest LCE savings. However, to fulfill more far-reaching operational energy savings, application of additional retrofitting measures was required, increasing the embodied energy use considerably and resulting in lower LCE savings compared to the optimal retrofitting solution that only reached the Swedish new-build energy standard. The LCE difference between the optimal retrofitting solutions that fulfilled the new-build standard and the strictest near-zero (passive house) standard was 1862 GJ, which is equivalent to almost four years of operational energy use for the original building. This indicates that there is a limit to the reduction of operational energy use when retrofitting existing buildings, beyond which additional reductions can considerably increase the embodied energy and thus be unfavorable in terms of LCE use.

The building design process is crucial in efforts to implement energy-efficient practices by adopting Energy Efficiency Measures (EEMs). However, design choices based solely on reducing operational energy use can significantly increase a building's embodied energy and Life Cycle Energy (LCE) use, because there is a trade-off between embodied and operational energy. This article presents a case study in which multi-objective optimization was used to explore the effects of various EEMs on the aforementioned trade-off. Optimal solution(s) for six different building shapes (rectangular, H-, U-, l-, T- and cross-shaped) based on two sets of EEMs were investigated and compared. The first set of EEMs consisted of EEMs that can be implemented or modified during the early design phase, such as the building's shape, orientation, Window to Wall Ratio (WWR), and constituent materials. The second set comprised EEMs that can be implemented later in the design phase (i.e. EEMs relating to the constituent materials). The LCE reductions achieved by finding optimal solutions for EEMs in the first set (ranged from 2175.2 to 3803.8 GJ) were significantly (over 5 times) higher than those achieved for the second set (ranged from 418.6 to 625.6 GJ) for all building shapes. Moreover, LCE use for pre-optimization building designs varied significantly with building shape. However, after optimization, the differences in LCE use between the optimal solutions of different building shapes were modest. This means that designers and construction companies can select building shapes based on customer requirements, but also highlights the importance of using multi-objective optimization during early design process to identify optimal combinations of EEMs that minimize LCE use.

Virtual design tools and methods can aid in creating decision bases, but it is a challenge to balance all the trade-offs between different disciplines in building design. Optimization methods are at hand, but the question is how to connect and coordinate the updating of the domain models of each discipline and centralize the product definition into one source instead of having several unconnected product definitions. Building information modelling (BIM) features the idea of centralizing the product definition to a BIM-model and creating interoperability between models from different domains and previous research reports on different applications in a number of fields within construction. Recent research features BIM-based optimization, but there is still a question of knowing how to design a BIM-based process using neutral file formats to enable multidisciplinary optimization of life-cycle energy and cost. This paper proposes a framework for neutral BIM-based multidisciplinary optimization. The framework consists of (1) a centralized master model, from which different discipline-specific domain models are generated and evaluated; and (2) an optimization algorithm controlling the optimization loop. Based on the proposed framework, a prototype was developed and used in a case study of a Swedish multifamily residential building to test the framework’s applicability in generating and optimizing multiple models based on the BIM-model. The prototype was developed to enhance the building’s sustainability performance by optimizing the trade-off between the building’s life-cycle energy (LCE) and life-cycle cost (LCC) when choosing material for the envelope. The results of the case study demonstrated the applicability of the framework and prototype in optimizing the trade-off between conflicting objectives, such as LCE and LCC, during the design process.

Design choices with a unilateral focus on the reduction of operational energy for developing energy-efficient and near-zero energy building practices can increase the impact of the embodied energy, as there is a trade-off between embodied and operational energy. Multi-objective optimization approaches enable exploration of the trade-off problems to find sustainable design strategies, but there has been limited research in applying it to find optimal design solution(s) considering the embodied versus operational energy trade-off. Additionally, integration of this approach into a Building Information Modeling (BIM) for facilitating set up of the building model toward optimization and utilizing the benefits of BIM for sharing information in an interoperable and reusable manner, has been mostly overlooked. To address these issues, this paper presents a framework that supports the making of appropriate design decisions by solving the trade-off problem between embodied and operational energy through the integration of a multi-objective optimization approach with a BIM-driven design process. The applicability of the framework was tested by developing a prototype and using it in a case study of a low energy dwelling in Sweden, which showed the potential for reducing the building’s Life Cycle Energy (LCE) use by accounting for the embodied versus operational energy trade-off to find optimal design solution(s). In general, the results of the case study demonstrated that in a low energy dwelling, depending on the site location, small reductions in operational energy (i.e. 140 GJ) could result in larger increases in embodied energy (i.e. 340 GJ) and the optimization process could yield up to 108 GJ of LCE savings relative to the initial design. This energy saving was equivalent to up to 8 years of the initial design’s operational energy use for the dwelling, excluding household electricity use.

Buildings account for 40% of all energy use in European countries. The European Union (EU) therefore encourages member states to adopt Energy Efficiency Measures (EEMs) and implement energy-efficient practices during building design to minimize the energy use of buildings. However, recent studies have shown that energy-efficient buildings may not always outperform conventional buildings in terms of Life Cycle Energy (LCE) use. This is mainly due to the trade-off between embodied and operational energy, and a reliance on EEMs that reduce operational energy while sometimes increasing embodied energy and LCE use. To improve buildings’ environmental performance, the impact of different EEMs on buildings’ energy use needs to be assessed from a lifecycle perspective, and methods for identifying optimal combinations of EEMs that minimize LCE use should be developed. Ideally, these methods should be integrated with building information modelling (BIM) to enable seamless data exchange and to help Architecture, Engineering and Construction (AEC) practitioners make optimal design decisions relating to EEMs. The work presented in this thesis had two overall objectives: (1) to explore the scope for developing BIM-supported method(s) for assessing and optimizing the impact of EEMs on buildings’ LCE use during the design process, and (2) use the BIM-supported method(s) for exploring the impact of various EEMs that are implemented and modified during the building design process on the buildings’ LCE use.

The work presented in this thesis is based on an exploratory research design involving iterative cycles of (1) problem identification, (2) method development, (3) method examination, and (4) theory suggestion. In step 1, problems were identified by conducting literature studies and workshops with AEC practitioners, and analyzing archival data. In step 2, prototyping was used to develop methods to overcome the identified problems. In step 3, the applicability of these methods (or prototypes) was tested in case studies on actual and hypothetical building projects. Three case studies were conducted – one dealing with a low energy dwelling located in Kiruna, Sweden; another dealing with a multifamily residential building in Uppsala, Sweden; and a third dealing with a hypothetical multifamily residential building in Stockholm, Sweden. In step 4, the results were compared to existing theories to strengthen existing knowledge and identify previously unrecognized findings.

In relation to the first objective, the results obtained show that the factors and activities required to develop BIM-supported method(s) for assessing and optimizing the impact of EEMs on a building’s LCE use during the design phase are:

• A database that stores external and building project data (e.g. BIM data) and links it to be used for assessment and optimization, providing access to the data whenever needed.

• The development of interfaces using middleware applications to ensure interoperability and seamless automated exchange of information between BIM and other systems.

• Predefined objects (i.e. building part and component recipes) that are stored in a database and linked to inventories and Environmental Product Declarations (EPDs) for the relevant materials, enabling assessment of the buildings’ embodied energy and LCE use.

• The application of multi-objective optimization techniques (e.g. Pareto-based genetic algorithms) to identify optimal solution(s) for EEMs that minimize (optimize) the building’s LCE use.

In relation to the second objective of the thesis, the results obtained indicate that:

• EEMs that are implemented and modified during the detailed design phase have much less influence on the building’s LCE use than those implemented in the early design phase. Highly influential EEMs related to the early design phase which were tested herein were the building’s shape, orientation, Window to Wall Ratio (WWR), and the selection of materials used in the building envelope.

• Generally, thickening roof insulation has a strong beneficial effect on LCE use for buildings in Sweden.

• For buildings using energy sources with high primary energy factors, the most effective way to reduce LCE use may be to implement many EEMs that reduce operational energy use. However, this approach may be less helpful for buildings using greener energy sources because in such cases the embodied energy may have a greater effect on the final LCE use.

• The embodied energies of materials in the same class can vary significantly between suppliers. Such differences in embodied energy can be identified by considering the suppliers’ EPDs, the energetic contributions due to their mode of transportation from the site of production, and the distance between the site of production and the construction site.

• If the developed optimization approach is used to identify optimal combinations of EEMs in the early design phase, designers can freely choose from a wide range of building shapes without greatly affecting LCE use. However, without early phase optimization, designs that use different building shapes may exhibit significantly different LCE use values.

The results provide both theoretical and practical contributions that may be useful to researchers and AEC practitioners seeking to develop BIM-supported design processes and to reduce buildings’ LCE use by adopting appropriate EEMs. The results also show that embodied energy can be a major component of a building’s LCE use if the building’s design relies heavily on EEMs designed solely to reduce operational energy use. Policy makers and governmental bodies are thus advised to update regulations and building codes to reflect the importance of embodied energy so as to minimize the LCE use of new and retrofitting building projects.

The building sector contributes significantly to the energy use and related greenhouse gas (GHG) emissions. Prior research has mainly focused on the impacts associated with material selection and building operation, thereby the embodied impact of the construction phase has got limited attention. The construction phase usually suffers from an inherent uncertainty in which construction operations, activities, and resources interact with each other in a complex manner. The discrete event simulation (DES) has been recognized to be a consistent simulation approach to capture these uncertainties and interactions. DES can also complement conventional life cycle assessment (LCA) tools, used for sustainable design and environmental strategies. However, the major challenge has been the implementation of the DES into practice which needs significant effort and work in order to create a realistic model of the construction process. To overcome this obstacle, this paper proposes a framework that integrates building information modeling (BIM), DES, and LCA in order to support the environmental evaluation and also facilitate implementation of the DES model by utilizing the data-rich BIM. Finally, the practical application of the proposed BIM-DES-LCA framework is demonstrated in a preliminary prototype and the areas where further development is required have been highlighted to address in future research

Assessment of the embodied energy associated with the production and transportation of materials during the design phase of building provides great potential to profoundly affect the building’s energy use and sustainability performance. While Building Information Modeling (BIM) gives opportunities to incorporate sustainability performance indicators in the building design process, it lacks interoperability with the conventional Life Cycle Assessment (LCA) tools used to analyse the environmental footprints of materials in building design. Additionally, many LCA tools use databases based on industry-average values and thus cannot account for differences in the embodied impacts of specific materials from individual suppliers. To address these issues, this paper presents a framework that supports design decisions and enables assessment of the embodied energy associated with building materials supply chain based on suppliers’ Environmental Product Declarations (EPDs). The framework also integrates Extract Transform Load (ETL) technology into the BIM to ensure BIM-LCA interoperability, enabling an automated or semi-automated assessment process. The applicability of the framework is tested by developing a prototype and using it in a case study, which shows that a building’s energy use and carbon footprint can be significantly reduced during the design phase by accounting the impact of individual material in the supply chain.

Recent studies indicate that the embodied energy originating from the buildingmaterial supply chain (i.e. off-site production of materials and components andassociated transportation to the construction site) contributes significantly tothe total life-cycle energy use. Therefore, considering its impact during thebuilding design and pre-construction stage provides an opportunity to affect thebuilding energy use and sustainability performance. However, there are twomajor shortcomings with the life cycle assessment (LCA) tools used forassessment and reduction of the embodied energy use during the buildingdesign and pre-construction stage. (1) Many of the LCA tools use databasesbased on industry-average values which hinders the possibility to account forthe differences in the embodied impact of specific materials sourced fromindividual suppliers. (2) Lack of interoperability between the LCA tools andthe Building Information Modeling (BIM) software which has become an assetfor supporting decisions during building design and pre-construction. Thisinteroperability issue increases the amount of time and effort required forassessment of the embodied energy and also increases the risks for mistakes,misunderstandings and errors due to the manual re-entry of BIM data into the LCA tools.

Therefore, the overall purpose of the research is to investigate the possibility tomitigate the aforementioned shortcomings by integrating the analyses of theembodied energy into a BIM-driven design process. Two research questionshave been defined: (1) What is a suitable data source for assessment of theembodied energy? (2) How can the embodied energy assessment be integratedinto a BIM-driven design process?

To address the first research question in identifying a suitable data source forassessing the embodied energy, literature studies were conducted to provideinsights into the existing Life-Cycle Inventory (LCI) data used for assessmentof the embodied energy. To address the second research question, several caseswere studied using a prototyping approach which enabled the identification ofrequired processes and functions for supporting assessment of the embodiedenergy in a BIM-driven design process.

The result of the literature studies and answer to the first research questionindicate that Environmental Product Declaration (EPD) of materials andcomponents can be recognized as a suitable data source for assessment of theembodied energy. EPDs provide a detailed LCA data for a specific productwhich is implemented according to Product Category Rules (PCR) and verifiedby an independent third party. PCRs provide pre-established guidelines andrequirements for the LCA of a certain product category and by this meanensure the principle for comparability of the LCA data. The main outcome ofthe second research question is a framework which highlights the requiredprocesses for facilitating and supporting assessment of the embodied energy ina BIM-driven design process. The framework uses the suppliers’ EPDs tosupport the design decisions and enable assessment of the embodied impactcaused by the building material supply chain. The framework also ensuresBIM-LCA interoperability by integrating the Extract, Transform Load (ETL)technology with BIM, enabling an automated or semi-automated assessmentprocess, to reduce the amount of time, efforts and risks for mistakes that wasreported to be the major obstacles within the embodied energy assessment.

Construction and operation of buildings and infrastructure is a main contributor to emissions of greenhouse gases (GHG) in Sweden. The embodied energy of construction, meaning all the energy that is used until the completion of the construction project (see Figure 1), cause roughly 10 million tones of CO2 equivalent emissions each year which equals to the emissions from all cars in Sweden (IVA 2014). About 6 million tones of CO2 equivalent emissions are attributed to the embodied energy of roads, railroads and other civil works while the remaining 4 million tones are attributed to the embodied energy of buildings (IVA 2014). Although reducing energy use and associated GHG-emissions in road and railroad construction is prioritized by the Swedish Transport Administration (Trafikverket 2012), the GHG-emissions from such construction projects have increased in recent years (Boverket 2014). Many of the existing efforts to reduce energy use and associated GHG-emissions focus on individual phases of the life cycle and don’t take into consideration the effects at other stages during the whole life cycle of a project (Boverket 2011). A crucial step in the assessment of energy use and associated GHG-emissions is to clarify and categorize the different phases of a life cycle. Figure 1 shows a proposed categorization of life cycles phases and use of energy based on previous research (Davies et al. 2014). Buildings’ main use of energy happens during its operational phase from e.g. heating, lighting and use of electrical appliances (Sartori and Hestnes 2007). In infrastructure projects such as road construction the embodied energy is roughly equal to the operational energy for roads with lighting, or in fact considerably higher if the road lacks lighting (Stripple 2001).