Integrated BIM-Based LCA for the Entire Building Process Using an Existing Structure for Cost Estimation in the Swiss Context

Round 1

Reviewer 1 Report

As a reviewer I declare that I am very knowledgeable in the area of integrating BIM, LCA and cost estimating for building projects.

The manuscript title “Integrated BIM-based LCA for the entire building process using existing structure for cost estimation” is a very interesting research topic, however that title is completely mis-leading the manuscript’s content, which is mainly focusing on the Swiss construction industry, therefore the title needs to be modified to include toward the end of the title “in the Swiss industry”.

The list of references of that manuscript is not comprehensive, it is evident that the authors did not look at all the research studies done in that area, by not doing so they made their manuscript very weak.

The objectives are not clear as well as the adopted methodology, which is another indication about the weakness of this study.

After reading this manuscript, the reviewer concluded that the authors are not distinguishing between BIM as a concept and its tools. Page 7 line 241, the authors wrote: “…and incorporated in the BIM.” What is this? Wat does this mean?

Page 7, line 248, they wrote: “…to the calculation of LCA values”, LCA is a method used to calculate specific values, how can a method has values?

The figures and tables do not have any additional value to the manuscript since they are not clear, are not placed in their correct place and are not explained in detail.

The manuscript has some typos that need to be fixed.

Author Response

Response to Reviewer 1 Comments

Point 1: The manuscript title “Integrated BIM-based LCA for the entire building process using existing structure for cost estimation” is a very interesting research topic, however that title is completely mis-leading the manuscript’s content, which is mainly focusing on the Swiss construction industry, therefore the title needs to be modified to include toward the end of the title “in the Swiss industry”.

Response 1:

Manuscript’s title

Thank you for the comment. The manuscript’s title has been changed accordingly to „Integrated BIM-based LCA for the entire building process using an existing structure for cost estimation in the Swiss context“, in order for the relationship of the manuscript’s context to the Swiss building construction environment be highlighted.

Point 2: The list of references of that manuscript is not comprehensive, it is evident that the authors did not look at all the research studies done in that area, by not doing so they made their manuscript very weak.

Response 2:

Manuscript’s references

Thank you for the comment! We rechecked our references and added:

1. Abanda, F.H., Oti, A.H., Tah, J.H.M., Integrating BIM and new rules of measurement for embodied energy and CO2 assessment, Journal of Building Engineering, 2017, 12, 288–305, doi: 10.1016/j.jobe.2017.06.017;
2. Chang, Y. Qi, S., Ji, Y., Qi, K., BIM-based incremental cost analysis method of prefabricated buildings in China, Sustainability, 2018, 10(11), 4293, doi: 10.3390/su10114293;
3. Eleftheriadis, S., Mumovic, D., Greening, P., Life cycle energy efficiency in building structures: A review of current developments and future outlooks based on BIM capabilities, Renewable and Sustainable Energy Reviews, 2017, 67, 811–825, doi: 10.1016/j.rser.2016.09.028;
4. Hollberg, A., Genova, G., Habert, G., Evaluation of BIM-Based LCA Results for Building Design, Automation in Construction, 2020, 109, 102972, doi: 10.1016/j.autcon.2019.102972;
5. Lasvaux, S., Gantner, J., Towards a new generation of building LCA tools adapted to the building design process and to the user needs, Sustainable Building, 2013, 406–417;
6. Lee, S., Tae, S., Roh, S., Kim, T., Green Template for Life Cycle Assessment of Buildings Based on Building Information Modeling: Focus on Embodied Environmental Impact, Sustainability, 2015, 7-12, 16498–16512, doi: 10.3390/su71215830;
7. Najjar, M., Figueiredo, K., Palumbo, M., Haddad, A., Integration of BIM and LCA: Evaluating the environmental impacts of building materials at an early stage of designing a typical office building, Journal of Building Engineering, 2017, 14, 115–126, doi: 10.1016/j.jobe.2017.10.005;
8. Röck, M., Hollberg, A., Habert, G., Passer, A., LCA and BIM: Integrated Assessment and Visualization of Building Elements’ Embodied Impacts for Design Guidance in Early Stages, Procedia CIRP, 2018, 69, 218-223, doi: 10.1016/j.procir.2017.11.087;
9. Russell-Smith, S., Lepech, M. D., Fruchter, R., Meyer, Y., Sustainable Target Value Design: Integrating Life Cycle Assessment and Target Value Design to Improve Building Energy and Environmental Performance, Journal of Cleaner Production, 2015, 88, 43-51, doi: 10.1016/j.jclepro.2014.03.025;
10. Seyis, S., Mixed method review for integrating building information modelling and life cycle assessments, Building and Environment, 2020, 173, 106-703, doi: 10.1016/j.buildenv.2020.106703;
11. Wong, J.K.W., Zhou, J., Enhancing environmental sustainability over building life cycles through green BIM: A review, Automation in Construction, 2015, 57, 156–165, doi: 10.1016/j.autcon.2015.06.003.

We did not refer to all papers related to BIM and LCA, because we do not think this is necessary for the objective of the paper. We, therefore, instead referred to recent review papers that looked at all the publications in detail. 

Point 3: The objectives are not clear as well as the adopted methodology, which is another indication about the weakness of this study.

Response 3:

Page 1, lines 31-41

Page 3, lines 100-114

Page 4, lines 178-182

Page 5, lines 183-188

Thank you for the comment. We reworked the phrasing of the objective in the subtract and the introduction. We think the objective is clearly stated in Page 3, lines 100-114 as „The main objective of this paper is to develop an integrated BIM-LCA workflow for the entire building process using an existing structure for cost estimation in Switzerland. By using this established and widely adopted structure, the novel approach aims at minimising the need for re-entering data and the usage of many different software tools. It should provide a methodology for Swiss companies to perform LCA continuously over the whole building process without additional effort.“ The methodology is further elaborated on as on page 4, line 178: „The method for developing an integrated BIM-LCA workflow for the whole building process consists of four main steps. First, the relationship between the building phases in Switzerland (SIA) and the Level of Development (LOD) is identified. Second, the relationship between LCA databases in Switzerland and the Swiss cost-planning structure (eBKP-H) is determined. Third, based on the relation between the building phases, the LOD, the LCA databases and the cost-planning structure, a new, process-structured LCA database for building components is developed. Fourth, the newly developed LCA database is connected to a BIModel employing a dynamic tool. The tool is applied in a case study building to validate the applicability throughout the building process. The methodology is used for the evaluation of the structural elements part of the BIModel of the case study. The general concept behind the methodology is to connect the workflow for BIM-LCA integration to the one used for cost estimation by adopting the same BIM elements code-structure.“

Point 4: After reading this manuscript, the reviewer concluded that the authors are not distinguishing between BIM as a concept and its tools. Page 7 line 241, the authors wrote: “…and incorporated in the BIM.” What is this? Wat does this mean?

Response 4:

Page 2, lines 66-72

Throughout the text

Thank you for the comment. We now differentiate between the method Building Information Modelling (BIM) and the Building Information Models (BIModels) in the text. Furthermore, the following terms are now highlighted in the text:

Building Information Modelling (BIM): Building Information Modelling (BIM) is a set of technologies, processes and policies enabling multiple stakeholders to collaboratively design, construct and operate a facility in virtual space.

Building Information Modelling techniques (BIModelling techniques): The techniques used as a concept to establish the BIM structure incorporated in the BIModel.

Building Information Model (BIModel): Building Information Model (BIModel) is the object-based, data-rich, 3D digital model generated by a project participant using a BIM Software Tool.

BIM structure: The structure used to create the geometry and the information associated with it in the BIModel.

BIM software tool: The software applications which can author an object-based, data-rich, 3D model.

Point 5: Page 7, line 248, they wrote: “…to the calculation of LCA values”, LCA is a method used to calculate specific values, how can a method has values?

Response 5:

Page 3, lines 133-143

Page 4, lines 144-145

Thank you for the comment. We added further information on the pre-calculated values that are used in Switzerland in section 2.2 LCA databases for buildings in Switzerland starting in Page 3, lines 133-143: „In contrast to conventional LCA, most LCA studies for buildings use predefined data such as Environmental Product Declarations (EPD) or values from building material LCA databases. As such, the Life Cycle Inventory (LCI) and Life Cycle Impact Assessment (LCIA) as defined in ISO 14040 are merged into one stage (Lasvaux et al., 2013). The quantities of different materials can be directly multiplied with the values from an LCA database. The Swiss LCA databases contain different environmental indicators, including grey energy (SIA, 2019), GHG emissions (World Green Building Council, 2020) and a single-score indicator called Umweltbelastungspunkte/ Environmental impact points (UBP). This indicator is calculated explicitly for Switzerland based on the method of ecological scarcity (Frischknecht et al., 2013). In this study, the LCA calculation is evaluated with LCA values and LCA benchmarks. The LCA values provide information for environmental indicators of a specific material or component, whereas LCA benchmarks suggest a recommended estimation.

Different Swiss LCA databases for buildings use different reference units for the LCA values. All these databases use LCA data from Ecoinvent Version 2.2 (ecoinvent, 2020).“

Point 6: The figures and tables do not have any additional value to the manuscript since they are not clear, are not placed in their correct place and are not explained in detail.

Response 6:

Throughout the text

We removed Figure 1 and checked the placing of the figures.

Point 7: The manuscript has some typos that need to be fixed.

Response 7:

Throughout the text

We did a language check of the whole manuscript.

Reviewer 2 Report

The topic could be interesting, but I think it's need more research activity with many more case studies.
The aim is to have more feedback on the goodness of the results and the processes follow.
It's suitable to outline future developments in a more practical way.

Author Response

Response to Reviewer 2 Comments

Point 1: The topic could be interesting, but I think it's need more research activity with many more case studies. The aim is to have more feedback on the goodness of the results and the processes follow. It's suitable to outline future developments in a more practical way.

Response 1:

Thank you for the comment. We agree that further case studies would support the proving of the validity of the approach and would be needed to evaluate the accuracy of the results. However, the objective of this paper was to develop a method based on the existing cost estimation structure, and the respective workflow applied in BIM. The case study saves the need from exemplifying the application of the method. As such, we believe that it was proved that it could be applied. The topic is further elaborated in Implenia by some of the authors of the manuscript. In the future, a study of assessing multiple real buildings would be valuable to evaluate the accuracy of results.

Reviewer 3 Report

The authors of this manuscript integrated the LCA methodology with BIM tools to demonstrate the feasibility of performing a continuous LCA study throughout the building process. This field is currently a hot topic in the domain of digital tools and sustainable construction. The manuscript is well written, and the methodology is suitable to the study. The discussion of the study results and limitations are also pertinent for future research on this domain. Therefore, I believe the manuscript has potential to be published if some minor improvements are done.

The linkage between BIM-LCA with “an existing structure for cost estimation” is not clear in the initial sections of the manuscript. You discuss the sustainability of construction and the role of BIM and LCA but suddenly a cost estimation structure is mentioned. Why is that? Why is it relevant to this study? Is the focus of the study the environmental impacts (LCA) or LCA + cost estimation? This should be clarified at the beginning of the manuscript.

The methodology and discussion sections are clear and well described. However, the presentation of the results is somehow lacking, in my opinion. You have described the case study and then presented briefly your results (1 page), which did show how useful your method is to the readers. After reading the result section, I am not aware of the environmental impacts of the case study, typology of the case study, if it was an LCA study that focused on the A modules (product + construction stages) or if it also covered other modules, or even the materials that were used in that case study. Summing up, apart from the case study location, area, and type of usage, everything is very vague.

Furthermore, have you compared the results between the impacts calculated using the SIA2040 database (component-based approach) with a more precise analysis (material-based approach)? Figure 7 highlights some discrepancies between different LODs but is not enough so that the readers understand the difference (e.g. percentage) of using an approach or the other.

Which LCA stages are considered in your study? From my understanding, only phase 6 considers the service life of the materials used in the construction. This phase covers the use stage or end-of-life as well? But the results and discussion section does not go into detail about this as well.

The proposed BIM-LCA method focuses on which domains? Architectural and Structural elements? Or is also able to cover MEP elements?

Author Response

Response to Reviewer 3 Comments

Point 1: The linkage between BIM-LCA with “an existing structure for cost estimation” is not clear in the initial sections of the manuscript. You discuss the sustainability of construction and the role of BIM and LCA but suddenly a cost estimation structure is mentioned. Why is that? Why is it relevant to this study? Is the focus of the study the environmental impacts (LCA) or LCA + cost estimation? This should be clarified at the beginning of the manuscript.

Response 1:

Page 1, lines 31-41

Page 2, lines 93-96

Page 3, lines 97-114

Thank you very much for the comment! We now made it more explicit that the approach just makes use of the established and widely adopted cost estimation structure as a means to integrate LCA in the planning process. We added background information about the cost estimation workflow in page 2, line 93: “Therefore, there is a need to use already existing BIM workflows and structures for the application of LCA. Such an established computational workflow is cost estimation. Cost estimation computations are regularly applied, and their workflow precisely developed in each part of the building process. BIM has been used for cost estimation in different LOD before (Chang et al., 2018). Furthermore, researchers have successfully linked Life Cycle Costing (LCC) and LCA (Santos et al., 2019). However, the resulting framework is new and very complex, leading to a reduction of the uptake by practitioners.

There is a potential for BIM-LCA integration by adding LCA specific data to the information required for cost estimation, building upon the existing workflow that companies already use today and as such giving companies the possibility to apply LCA methods without additional effort.”

Furthermore, we clarified the objective on page 3, lines 100-114 as „The main objective of this paper is to develop an integrated BIM-LCA workflow for the entire building process using an existing structure for cost estimation in Switzerland. By using this established and widely adopted structure, the novel approach aims at minimising the need for re-entering data and the usage of many different software tools. It should provide a methodology for Swiss companies to perform LCA continuously over the whole building process without additional effort.“

Point 2: The methodology and discussion sections are clear and well described. However, the presentation of the results is somehow lacking, in my opinion. You have described the case study and then presented briefly your results (1 page), which did show how useful your method is to the readers. After reading the result section, I am not aware of the environmental impacts of the case study, typology of the case study, if it was an LCA study that focused on the A modules (product + construction stages) or if it also covered other modules, or even the materials that were used in that case study. Summing up, apart from the case study location, area, and type of usage, everything is very vague.

Response 2:

Page 8, lines 296-310

Thank you for the comment. The description of the case study is further elaborated on as follows: „The case study itself is a mixed-use timber building called Krokodil (Figure 5). The building is located in the Lokstadt district, in Winterthur, Switzerland. The project uses a three-dimensional data model throughout the whole process, from the architectural competition to execution planning. It has started in 2016 and is expected to be completed in 2020. The gross floor area of the building is 31 559 m2. The building is composed of eight floors above ground level and two floors below. The timber construction of the building is composed of prefabricated elements and entitles for most of the structures used in the building, leading to a reduction of the embodied environmental impacts.

One of the main strategic goals of the project design is the achievement of the sustainability targets set by the 2000-Watt Society. 2000-Watt Society is a program created by The City of Zurich that defines target values for the 2050 year of 3500 Watts and 2 tonnes of CO2-eq per person. The program sets goals related to consumption, settlement, buildings, energy supply and mobility for reaching these target values. Regarding embodied environmental impacts, the program refers to the Swiss Minergie-ECO standard (City of Zurich, 2011). Minergie-ECO accounts for embodied energy used in buildings through the identification of grey energy (MJ), GHG (kg CO2-eq) and UBP (Pt.) (MINERGIE, 2014).“

Point 3: Furthermore, have you compared the results between the impacts calculated using the SIA2040 database (component-based approach) with a more precise analysis (material-based approach)? Figure 7 highlights some discrepancies between different LODs but is not enough so that the readers understand the difference (e.g. percentage) of using an approach or the other.

Response 3:

Page 9, lines 328-333

Page 10, lines 344-351

The newly created LCA database and the digital tool related to it account only for the simplified component-based approach, building phases 1 to 3. We further elaborated in the paper: „On Figure 6 (previous Figure 7), results derived after running the Dynamo scripts on BIModels from building sub-phases 22 (2 Preliminary Studies - 22 Selection Procedures), 31, and 32 (3 Project – 31 Schematic Design, 32 – Design Development) with different LOD regarding grey energy (MJ/a) are shown. The results account for the simplified component-based approach for LCA (Figure 2) by evaluating the different LOI in terms of embodied environmental impacts based on the different building phases. The results follow the evolution of the BIModel, providing more precise information in each further phase. The detailed material-based approach has not been included in the new process-structured LCA database, and thereforе is not part of the results.“

Point 4: Which LCA stages are considered in your study? From my understanding, only phase 6 considers the service life of the materials used in the construction. This phase covers the use stage or end-of-life as well? But the results and discussion section does not go into detail about this as well.

Response 4:

Page 5, lines 196-204

Thank you for this comment. We added the life cycle modules in the description on page 5, lines 196-204:  „The LCA databases used for the evaluation of the building process are the Bauteilkatalog and the KBOB database. The Bauteilkatalog provides information regarding the simplified component-based approach, while the KBOB database serves for the evaluation of the detailed material-based one. The information in both the Bauteilkatalog and the KBOB database is derived according to Ecoinvent data Version 2.2 (ecoinvent, 2020) and covers life cycle modules A1-A3 (production), B4 (replacement) and C3-C4 (disposal) (EN 15804:2012, 2012; ISO 14025:2006, 2006). This information is then used and evaluated per year of building life cycle for building phases 1-5. For building phase 6, information regarding the Reference Service Life (RSL) is used to identify when should the materials part of the building be changed.“

Point 5: The proposed BIM-LCA method focuses on which domains? Architectural and Structural elements? Or is also able to cover MEP elements?

Response 5:

Page 4, lines 178-182

Page 5, lines 183-188

Page 11, lines 375-377

Page 13, lines 484-485

Page 13, lines 501-503

The methodology is used for the evaluation of structural elements part of BIModels. The limitations regarding the incompleteness of BIModels concerning the lack of information about MEP elements are discussed on page 11, lines 375-377. Future potential about the provision of data in LCA databases (page 13, lines 484-485) and the dynamic tool for LCA (page 14, lines 501-503) are further elaborated on.

Round 2

Reviewer 2 Report

I think the review has achieved the objectives necessary to be published.

Reviewer 3 Report

After carefully reading the reviewed manuscript, I've verified that all my concerns were addressed by the authors. 

Therefore, I believe that the manuscript has enough quality to be published in the Sustainability journal.