An LCA Study of Various Office Building Shapes Focusing on Operational Energy—A Case of Hamburg

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. The introduction. Summary of existing studies should be more concise and clear. You don't need to explain each of them using 2-3 paragraphs. This is not the way of writing a journal paper. It reads like a student report.

2. The energy demand was calculated by equations. This way is outdated and not scientific. It is a norm nowadays to use energy simulation software like Energy Plus or others to calculate the energy demand. I suggest you conduct energy simulations, which is more acceptable, and then you will need to list in detail all the settings you used for the simulations, but you don't need to list those equations in the paper.

3. How did you get the environmental impacts? Which software did you use? It is not clear in the manuscript.

4. This is NOT a life-cycle assessment. You didn't involve embodied carbon and you didn't calculate the operation energy either. You should change the title.

5. Overall, the study is too simple and many of the methodology details are not clear or scientific. The writing style is too casual - e.g., one single sentence was a paragraph. 

 

Comments on the Quality of English Language

Use academic style English

Author Response

Dear Reviewer 1,
Thank you for your comments.

Comment 1: The introduction. Summary of existing studies should be more concise and clear. You don't need to explain each of them using 2-3 paragraphs. This is not the way of writing a journal paper. It reads like a student report.

Response 1: The introduction has been reworked and condensed to align with academic writing standards. New content and references have also been incorporated to enhance the discussion.You can review the revised version in lines 29 to 114 of the updated manuscript.

Comment 2: The energy demand was calculated by equations. This way is outdated and not scientific. It is a norm nowadays to use energy simulation software like Energy Plus or others to calculate the energy demand. I suggest you conduct energy simulations, which is more acceptable, and then you will need to list in detail all the settings you used for the simulations, but you don't need to list those equations in the paper.

Response 2: The use of a software is no guarantee for scientific accuracy. The equations used in this study are transparent, adhere to German standards, and represent the current state of the art. While simulation software can be useful, it may lack transparency, and its algorithms or procedures can also be outdated. By using equations, we ensure the reliability and reproducibility of the results.

Comment 3: How did you get the environmental impacts? Which software did you use? It is not clear in the manuscript.

Response 3: The tool used for environmental impact calculations, 'eLCA,' is clearly mentioned in Section 2, Methodology. Additionally, a more detailed explanation of the software has been included in the revised manuscript, which can be found in lines 190 to 211.

Comment 4: This is NOT a life-cycle assessment. You didn't involve embodied carbon and you didn't calculate the operation energy either. You should change the title.

Response 4: LCA outcomes are always dependant on the chosen boundary conditions. In this study, the impact of materials was excluded due to high variability, which would compromise comparability. Additional impact indicators were calculated but were also excluded from the manuscript to maintain a clear focus on the principle of 'form follows energy.' This approach is consistent with several studies cited in the introduction, which also prioritize specific aspects for analysis.

Comment 5: Overall, the study is too simple and many of the methodology details are not clear or scientific. The writing style is too casual - e.g., one single sentence was a paragraph.

Response 5: We intentionally kept the methodology simple to provide a clear understanding of the energy impacts of building shapes, as simplicity can be a strength in conveying the topic and results. The methodology was visualised in the grafical abstract. Additional details on how the databases were used have been included (Line 190 to 211, line 591 to 606, line 721 to 736), and the language has been revised for clarity and formality (refer also to paragraph 1).

 

Reviewer 2 Report

Comments and Suggestions for Authors

The research work developed by the authors focuses on the comparison of different plan forms of office buildings located in Hamburg, relating building morphology, energy consumption and life cycle. The study focuses on different configurations, identifying a first set of aggregations resulting from the juxtaposition of six modular units, followed by other configurations of 8 modules, 10 modules and 12 modules with a courtyard. A second set is instead identified by other geometric shapes. For the different geometric shapes, a comparison is also made in terms of height, focusing on buildings with heights of 3, 6 and 12 m. Energy demand was calculated through the analysis of heat, lighting, hot water and total energy demand; an analysis of the environmental impacts in the various building forms completes the study.
The work carried out by the authors is interesting because it deals with a building type, the office building, that has been little investigated. The study is clear in its objectives and is also well argued in terms of the limitations of the research.
Some suggestions may help to improve the work carried out by the authors:
-please specify in the abstract what kind of calculations are performed: the expression ‘Through calculations and comparisons of the LCA results ’ is too general.

-specify the period within which the literature review was carried out
-explain the relationship between window area and wall area by comparing two examples (with different plan form) with the same surface area.
- indicate, before Figure 3, that an LCA study also includes an analysis of materials, and therefore this represents a limitation (as will be mentioned in the conclusion).

Author Response

Dear reviewer 2,

Thank you for your comments.

Comment 1: please specify in the abstract what kind of calculations are performed: the expression ‘Through calculations and comparisons of the LCA results ’ is too general.

Response 1: Details about the used tool and the LCA indicators have been added to the abstract for clarity. Additional information on this is provided in the revised manuscript, Methodology section, lines 190 to 211.

Comment 2: specify the period within which the literature review was carried out

Response 2: The period for the studies on building shape and LCA mentioned in the introduction is specified in line 124. The new studies added to the revised manuscript, lines 29 to 75, span from 2011 to 2024.

Comment 3: explain the relationship between window area and wall area by comparing two examples (with different plan form) with the same surface area.

Response 3: The relationship is explained in section 2.2.2 and the results reflect on that. Further examples would expand the scope of this study further that intended. 

Comment 4: indicate, before Figure 3, that an LCA study also includes an analysis of materials, and therefore this represents a limitation (as will be mentioned in the conclusion).

Response 4: A new section (Section 2.3: LCA Calculation) has been added to the Methodology in the revised manuscript, where we address this limitation. Please refer to lines 602 to 605 for further details.

Reviewer 3 Report

Comments and Suggestions for Authors

This is one paper with a more interesting research topic, but it still needs to be further revised, and the relevant comments are as follows:

1. The first part of the article has a lot of "introduction", which can be divided into two parts: introduction and research background.

2. There are problems with the format of some papers: for example, L135 should be on the upper side of the table, and L668 and L671 also have the same problem;

3. The case of Hamburg should be discussed in a separate section, and the targeted analysis of energy demand and other aspects should be carried out, and the idea from theory to practice should be used to illustrate the correctness of the thesis's views;

4. What is the logical relationship between part 2.2.1 of the paper, which is unclear and messy, and the basis for determining the indicators is further explained? What are the weights?

5. There are few references in the paper, especially in the past 3 years;

6. What is the current situation or status of the research on the topic of the paper in other countries or cities? Do they have commonalities with the city of Hamburg? Similar comparisons are missing;

7. The LCA method is the keyword, but only the operational energy phase (L821) is analyzed, and the analysis of the environmental impact of other stages on the building is missing, and the LCA framework (L11) mentioned in the paper is not found;

8. What is the basis for the data in Figures 3 to 5 in the calculation of GWP? The same problem exists in the calculation of PENRT. What is the relationship with the city of Hamburg? The text is not clear.

 

Author Response

Dear reviewer 3,

Thank you for your comments.

Comment 1: The first part of the article has a lot of "introduction", which can be divided into two parts: introduction and research background.

Response 1:  The introduction has been reworked and condensed to align with academic writing standards. New content and references have also been incorporated to enhance the discussion.

Comment 2: There are problems with the format of some papers: for example, L135 should be on the upper side of the table, and L668 and L671 also have the same problem;

Response 2:  These formatting issues have been corrected.

Comment 3: The case of Hamburg should be discussed in a separate section, and the targeted analysis of energy demand and other aspects should be carried out, and the idea from theory to practice should be used to illustrate the correctness of the thesis's views;

Response 3:  Hamburg is referenced solely for its climate conditions, which are necessary for calculating heating demand, as well as for other information specific to Hamburg required for lighting calculations based on German standards. These standards have been incorporated into the LCA calculations and the considered in inventory database used. Additionally, assumptions regarding energy production and the energy mix, outlined in Section 2.3 (lines 595 to 601), are specific to Germany and applicable to cities like Hamburg.

Comment 4:  What is the logical relationship between part 2.2.1 of the paper, which is unclear and messy, and the basis for determining the indicators is further explained? What are the weights?

Response 4:  First, operational energy was chosen as the focus of the study, and the indicators were selected accordingly. A more detailed explanation of this process has been added to the revised manuscript (lines 721 to 736). The final energy demand, calculated based on the equations introduced in Section 2.2.1, along with the energy demand for lighting, are used as inputs for the eLCA to calculate the environmental impacts. No weights are assigned to the environmental impact indicators, as they are analyzed separately in the Results section.

Comment 5:  There are few references in the paper, especially in the past 3 years;

Response 5:  The list of reviewed papers is indeed longer. However, only a few studies provide additional value to our paper. Some less relevant papers have now been added to offer a broader perspective on the related issues. Please refer to lines 29 to 114 for these updates. Among these are papers from recent years. 

Comment 6:  What is the current situation or status of the research on the topic of the paper in other countries or cities? Do they have commonalities with the city of Hamburg? Similar comparisons are missing;

Response 6:  The studies relevant to the impact of building shape and LCA, including cases from Southern Europe, Italy, Melbourne, and Spain, are discussed in the introduction (lines 77 to 114). However, this topic has not been extensively explored in other countries, and there is limited elaboration on similar comparisons in the existing literature.

Comment 7:  The LCA method is the keyword, but only the operational energy phase (L821) is analyzed, and the analysis of the environmental impact of other stages on the building is missing, and the LCA framework (L11) mentioned in the paper is not found;

Response 7:  LCA outcomes are always dependant on the chosen boundary conditions. In this study, the impact of other stages was excluded primarily because they are largely influenced by materials. Materials and their imapct was excluded due to their high variability, which would compromise comparability.

Additional impact indicators were calculated but were also excluded from the manuscript to maintain a clear focus on the principle of 'form follows energy.' This approach is consistent with several studies cited in the introduction, which also prioritize specific aspects for analysis.

The tool used for environmental impact calculations, 'eLCA,' is clearly mentioned in Section 2, Methodology. Additionally, a more detailed explanation of the software has been included in the revised manuscript, which can be found in lines 190 to 211.

Comment 8:  What is the basis for the data in Figures 3 to 5 in the calculation of GWP? The same problem exists in the calculation of PENRT. What is the relationship with the city of Hamburg? The text is not clear.

Response 8: The values are calculated with the software eLCA. See lines 190 to 211, and 591 to 606 for information on used databases and standards as well as our assumptions.  Again Hamburg is giving the climate conditions only.

 

 

Reviewer 4 Report

Comments and Suggestions for Authors

The presentation of an LCA study of different office building forms focusing on operational energy may be of importance to the industry. This study should clearly demonstrate its uniqueness in relation to other studies in the field. To emphasize the added value of the study, it is recommended to refer to the following comments.

1.      General comments

A. Abstract. The abstract consists of several disconnected paragraphs. It is important to connect the paragraphs into a single structure, as is customary.

B.  Section 1. The study repeatedly presents explanations for acronyms, such as GWP, PENRT. Authors are advised to present one explanation in the text for each acronym and to include a table of acronyms, as is customary.

C.  Section 3. Some titles use capital letters for each word and others do not. A uniform format for capital letters should be chosen as is customary.

2.      Specific comments

A.     Section 1. The introductory section is worded in a cumbersome manner, without clearly presenting the gap that needs to be bridged and how the authors seek to bridge it. It is recommended that the authors reword the introductory section, shortening it significantly, moving the literature review to a separate section, and explaining how this study is distinct from, builds on, and adds to studies conducted in the field.

B.     Section 2.

1)  The methodology section consists of insights that were not presented in a reasoned manner and parts that require substantiation and expansion. It is recommended that authors redraft the methodology section while presenting reasoned explanations for the key considerations in their research, including with regard to the choice of the office building, the manner of activity within it, and its data.

2)    The study mentions a significant geographical context without explaining its choice and importance. Since the study is specific to the climatic context of Hamburg, it is recommended that the authors present in a separate subsection the importance of the climatic region and the reason for choosing Hamburg in the context of the research question.

C.  Section 4. The study seeks to provide insights into the relationship between building form, energy performance and environmental impacts, but their integration into architectural design and urban planning processes requires extensive discussion and reference to previous studies. Authors are encouraged to present an extensive discussion of the results in the context of studies in the field, to establish the added value of the study.

D.  Section 5. The presentation of the limitations of the study should come after highlighting its advantages. Authors are advised to draft a summary section, which includes the limitations of the study and suggestions for its expansion, while emphasizing the analyses of heat demand, lighting demand, hot water demand, total energy demand, and environmental impacts across different building forms, to explain its added value relative to other studies.

 

Author Response

1. General comments

A. Abstract. The abstract consists of several disconnected paragraphs. It is important to connect the paragraphs into a single structure, as is customary.

Response: The format has been adapted.

B. Section 1. The study repeatedly presents explanations for acronyms, such as GWP, PENRT. Authors are advised to present one explanation in the text for each acronym and to include a table of acronyms, as is customary.

Response: The format of the journal requires the repetition of acronyms in abstract, text and first image/table. Anything additional to this has been fixed.  

C. Section 3. Some titles use capital letters for each word and others do not. A uniform format for capital letters should be chosen as is customary.

Response: The suggested changes have been accepted. Note: It would be better to refer to the formal requirements of the journal than to what is customary.

 

2. Specific comments

A. Section 1. The introductory section is worded in a cumbersome manner, without clearly presenting the gap that needs to be bridged and how the authors seek to bridge it. It is recommended that the authors reword the introductory section, shortening it significantly, moving the literature review to a separate section, and explaining how this study is distinct from, builds on, and adds to studies conducted in the field.

Response: The introduction has been slightly revised in line with the commentary. As the present form already contains the comments of other reviewers, a complete reformulation is not carried out here.

Please refer to lines 132 to 170 for addied details on how we are addressing the gaps.

 

B. Section 2.

1)  The methodology section consists of insights that were not presented in a reasoned manner and parts that require substantiation and expansion. It is recommended that authors redraft the methodology section while presenting reasoned explanations for the key considerations in their research, including with regard to the choice of the office building, the manner of activity within it, and its data.

Response: Hamburg is an industrial region, which is why office buildings play an important role. A corresponding explanation was added. By specifying “office buildings”, the activity in them and the associated impact on the test results is sufficiently defined within the framework of the standards used. Details on this can be found in the common standards mentioned.

Further details on the choice of office building shapes is now added. Refer to lines 246 to 302. 

2)    The study mentions a significant geographical context without explaining its choice and importance. Since the study is specific to the climatic context of Hamburg, it is recommended that the authors present in a separate subsection the importance of the climatic region and the reason for choosing Hamburg in the context of the research question.

Response: Hamburg is an industrial region, which is why office buildings play an important role. A corresponding explanation was added. The selection of a climate region is predetermined by the standard applied and partially influences the results. Without the selection of a climate region, the standard cannot be applied, which is why Hamburg was chosen as the location. A variation of the climate region is not the subject of the study. Rather, exemplary results for the energetic effect of different office building shapes are to be obtained.

Please refer to the added text in lines 160 to 166 an the existing section "Geographical context" line 420. 

C.  Section 4. The study seeks to provide insights into the relationship between building form, energy performance and environmental impacts, but their integration into architectural design and urban planning processes requires extensive discussion and reference to previous studies. Authors are encouraged to present an extensive discussion of the results in the context of studies in the field, to establish the added value of the study.

Response: Integration into architectural designs and urban planning processes is not the subject of this article. As architectural designs and urban planning processes have to consider many other aspects in addition to environmental impacts, this cannot be answered within the scope of this study.

However, an additional interpretation of our results from an architectural perspective is now added. Lines 894 to 916. 

 

D.  Section 5. The presentation of the limitations of the study should come after highlighting its advantages. Authors are advised to draft a summary section, which includes the limitations of the study and suggestions for its expansion, while emphasizing the analyses of heat demand, lighting demand, hot water demand, total energy demand, and environmental impacts across different building forms, to explain its added value relative to other studies.

Response: The study was carried out under the boundary conditions of a typical LCA with a focus on office buildings in Hamburg. The limitations of the study result from the continued focus of the work on energy performance. Other indicators of a full LCA, such as acidification potential or water consumption, were not included in the study. The evaluation of further indicators is planned in the next steps. This was already mentioned in the text.

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The methods have been detailed and explained better, and the writing has improved. However, I still think this study is not an LCA but an energy-related calculation. You can hold your opinion, but I think the title does not correctly reflect what you are doing.

Author Response

Dear Reviewer,

In response to your comment, we have revised the title to more accurately reflect the focus of our study and better indicate its energy-related analysis.

Reviewer 3 Report

Comments and Suggestions for Authors

I think the author has done their best to revise the paper. if possible,the content of the discourse could be further refined.

Author Response

Dear Reviewer,

We have reviewed the methodology and results sections and have further refined the content to ensure it better reflects the objectives and findings of our study. 

You can find either minor or major changes in the following pages: P.1, P.5, P.6, P.9, P.10, P.11, P.14, P.15, P.16, P.17, P.18, P.19, P.20, P.21, P.22, P.24

Reviewer 4 Report

Comments and Suggestions for Authors

For the purpose of presenting an LCA study of various shapes of office building that focuses on operational energy while emphasizing its added value, it is recommended to refer again to the following notes.

A.  Section 1. The introductory chapter is worded in a cumbersome manner and includes a literature review and a table that consist of offices and areas similar to the research topic without a clear distinction. It is recommended, again, that the authors rephrase the introductory chapter, shorten it significantly, move the literature review to a separate section, as is customary, present the research question, its importance, and how they intend to answer it.

B.   Section 4. In the short discussion section, the research presents a summary, stating that “the study provides insights into the relationship between building shape, energy performance, and environmental impacts” and adds that “by integrating these findings into architectural and urban planning processes, we can prepare for more efficient, environmentally conscious built environments”. However, these insights were not compared for validation with the literature in the field and the integration of the findings was not discussed at all. It is again recommended that the authors present an extensive discussion of the findings that places them in the relevant literature in the field.

C.  Section 5. The presentation of the limitations of the study should come after highlighting its advantages. It is recommended, again, that the authors draft a summary section, including the limitations of the study and suggestions for its expansion, emphasizing the analyses of heat demand, lighting demand, hot water demand, total energy demand, and environmental impacts across different building shapes, to explain its added value in relation to other studies.

Author Response

Dear Reviewer 4,

Your comments have been taken into consideration. 

Comment: A.  Section 1. The introductory chapter is worded in a cumbersome manner and includes a literature review and a table that consist of offices and areas similar to the research topic without a clear distinction. It is recommended, again, that the authors rephrase the introductory chapter, shorten it significantly, move the literature review to a separate section, as is customary, present the research question, its importance, and how they intend to answer it.

Response: The wording of the introduction section has been edited and significantly shortened. The introduction is now structured into three subcategories, with the literature review placed in a separate section, as recommended. (Lines 28 to 95). For further clarity, our research question is added and can be found in line 115. The importance of our study is elaborated in section 1.3. (lines 117 to 142) with lines 127 to 136 explaining how the previous two studies on office buildings lack comparability element and attention to specific office attributes. Our approach to addressing the research question is outlined in Lines 143–149.

 

Comment: B.   Section 4. In the short discussion section, the research presents a summary, stating that “the study provides insights into the relationship between building shape, energy performance, and environmental impacts” and adds that “by integrating these findings into architectural and urban planning processes, we can prepare for more efficient, environmentally conscious built environments”. However, these insights were not compared for validation with the literature in the field and the integration of the findings was not discussed at all. It is again recommended that the authors present an extensive discussion of the findings that places them in the relevant literature in the field.

Response: The integration of our study’s findings into the broader architectural and urban planning context was addressed in our previous revision, following your initial comments, though it is not the primary focus of this study. We refer you to lines 881 to 889 that is now located in the discussion section.  Additionally, we have now included a comparison of our results with existing literature for validation, which can be found in lines 893–926. This expanded discussion further contextualizes our findings within architectural and urban considerations.

 

Comment: C.  Section 5. The presentation of the limitations of the study should come after highlighting its advantages. It is recommended, again, that the authors draft a summary section, including the limitations of the study and suggestions for its expansion, emphasizing the analyses of heat demand, lighting demand, hot water demand, total energy demand, and environmental impacts across different building shapes, to explain its added value in relation to other studies.

Response: Thank you for your suggestion. We have restructured the discussion section to first highlight the advantages of our work and key findings, followed by the study’s limitations and directions for future research (Lines 867 to 943). Additionally, we have introduced a concluding section to summarize our findings.

Round 3

Reviewer 4 Report

Comments and Suggestions for Authors

It appears that in the additional version being examined, the authors made necessary corrections to parts of the study, which improve its presentation.