Sustainable Construction: The Embodied Carbon Impact of Infrastructures and Landscaping

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1.        Detailed Case Analysis:

This paper mentions that the impact of different cases on carbon emissions is studied through specific cases, and it is suggested that the specific calculation methods and data sources should be clarified in the case analysis to increase the transparency and credibility of the research.

2.        Graphs and Visualization:

Incorporate more charts and visualizations to present the data and analysis results, for example, using a bar or pie chart to illustrate the proportion of carbon emissions from the different materials of a building, or employing a flowchart to describe the study methodology.

3.        Mitigation Strategies and Recommendations:

The paper only points out the increasing trend of the proportion of the construction site in the total carbon emissions of the building, and does not put forward specific emission reduction countermeasures and suggestions.

4.        Practical Significance and Application:

The paper highlights the increasing share of infrastructure and landscaping in EC emissions, and suggests further research on the implications of this finding for actual architectural design and urban planning. For example, it is possible to discuss how the layout of infrastructure should be considered in the urban planning and design phase to reduce EC emissions, or to provide some successful case analyses.

Comments on the Quality of English Language

Minor editing of English language required

Author Response

Reviewer #1:

 

1. Detailed Case Analysis:

This paper mentions that the impact of different cases on carbon emissions is studied through specific cases, and it is suggested that the specific calculation methods and data sources should be clarified in the case analysis to increase the transparency and credibility of the research.

• Reply: Thank you for your comment. We have further described in section 4 the methods and calculation tools employed in our case studies. We have also added a note that the data in case 3 was only calculated and studied for comparative purposes, to verify/solidify the findings of our major case 2 and is therefore not presented in detail; page 5 lines 182 – 187.

 

2. Graphs and Visualization:

Incorporate more charts and visualizations to present the data and analysis results, for example, using a bar or pie chart to illustrate the proportion of carbon emissions from the different materials of a building, or employing a flowchart to describe the study methodology.

• Reply: Thank you for your comment. We have added pie charts at the end of section 6.2 (Fig. 4), visualizing the role of the site works in the low and high scenarios for our major case 2; page 11 lines 405 – 410.

 

3. Mitigation Strategies and Recommendations:

The paper only points out the increasing trend of the proportion of the construction site in the total carbon emissions of the building, and does not put forward specific emission reduction countermeasures and suggestions.

• Reply: Thank you for your suggestion. Although our focus here is to draw attention to a little researched “problem”, not solutions, we are very engaged in design solutions too, and have added a new section 8 outlining some key pointers towards solutions – connecting this to the paper by relating them to our four specified areas of urban design, materials, life cycle and climatic context. This helps to “tie the pieces together”, adding brief pointers to follow up these four areas noted; page 15 lines 542 to page 16 line 607.

 

4. Practical Significance and Application:

The paper highlights the increasing share of infrastructure and landscaping in EC emissions, and suggests further research on the implications of this finding for actual architectural design and urban planning. For example, it is possible to discuss how the layout of infrastructure should be considered in the urban planning and design phase to reduce EC emissions, or to provide some successful case analyses.

• Reply: Thank you for your comment. As above – we have added a little in this regard; page 5 lines 182 – 187.

 

 

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This work is interesting, and the work is completed and valuable. But it still needs the following improvement before publication.

1. The last section of the introduction section is not completed. It lacks to simply describe the how to carry out the current study and the further implication.

2. Please avoid to use the first name in the content.

3. It needs to state some values in the abstract and conclusion sections, which can directly display the essential findings from this study.

4. For the three cases in this study, it can not find the direct comparison results between each other. There is only some description to each one, some values/findings by comparing these three with different sites environment are lacking.

Author Response

Review #2:

This work is interesting, and the work is completed and valuable. But it still needs the following improvement before publication.

• The last section of the introduction section is not completed. It lacks to simply describe the how to carry out the current study and the further implication.
• Reply: Thank you for your comment. We have added lines to the introduction, with a brief description; page 3 lines 82 – 85.

 

• Please avoid to use the first name in the content.
• Reply: Thank you for your comment. The paper has been reviewed and edited; we have changed to “this study” or similar.

 

• It needs to state some values in the abstract and conclusion sections, which can directly display the essential findings from this study.
• Reply: Thank you for your comment. Our findings do contain specific figures, but we feel that since they are only indicative of orders of magnitude, we did not wish to place too much emphasis on concrete figures; page 1 lines 14 – 30.

 

• For the three cases in this study, it can not find the direct comparison results between each other. There is only some description to each one, some values/findings by comparing these three with different sites environment are lacking.
• Reply: Thank you for your comment. Please see our reply to point 3 above. However, we have added pie charts to better visualise the findings; page 11 lines 404 – 410.

 

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The paper discussed the embodied carbon impacts for buildings and the surrounding infrastructures. However, the whole paper is more like a review without clear methodology and results for the case study. Here are some suggestions for further improvements of the paper.

1.     Add one sentence stating the method used in the paper to the Abstract.

2.     The method part is unclear. What specific method did you use for calculating the embodied carbon? If you use LCA, then what’s your goal and scope for the LCA analysis? And what about the development of the inventory?

3.     How did you get the embodied carbon data in the case study?

4.     How to calculate the embodied carbon for site works and landscaping? What’s the difference between embodied carbon impact for buildings and the surroundings?

5.     What’s the major goal and contribution of the paper?

6.     The results are not supported with sufficient method and materials.

 

7.     Any logic or clue for the discussion? Is the discussion based on the findings of the study?

Comments on the Quality of English Language

Minor editing of English language required

Author Response

Review #3:

The paper discussed the embodied carbon impacts for buildings and the surrounding infrastructures. However, the whole paper is more like a review without clear methodology and results for the case study. Here are some suggestions for further improvements of the paper.

1. Add one sentence stating the method used in the paper to the Abstract.

• Reply: We appreciate your recommendation. The whole abstract has been revised now; page 1 lines 4 – 30.

 

2. The method part is unclear. What specific method did you use for calculating the embodied carbon? If you use LCA, then what’s your goal and scope for the LCA analysis? And what about the development of the inventory?

• Reply: Thank you for your comment. We have further described in section 4 the methods and calculation tools employed in our case studies. However, we have also added a note that the data in case 3 was only studied for comparative purposes, to verify/solidify the findings of our major case 2, and is therefore not presented in detail. The LCA scope – in our case broadly cradle to cradle – is now briefly noted. The development of the construction data is also described a little more however with the same underlined point that we have intentionally put together a simplified data picture corresponding to the major EC factors. Quantities are from design documents and drawings (cases 1 and 3) and in addition BoQs and site visits (case 2). Please see page 5 lines 182 – 187.

 

3. How did you get the embodied carbon data in the case study?

• Reply: Thank you for your question. Data: sources are principally ICE and OneClick and we also cross-check their figures with other EC figures we have become familiar with. Calculations are in all cases our own.

 

4. How to calculate the embodied carbon for site works and landscaping? What’s the difference between embodied carbon impact for buildings and the surroundings?

• Reply: Thank you for your comment. We have now in section 4, discussed more about the methods and calculation tools employed in our case studies; page 5 lines 182 – 187.

 

5. What’s the major goal and contribution of the paper?

• Reply: Thank you for your comment. We have added sentences to better express that the major goal has been to identify and illustrate, with simple case analyses, a relatively new and original perspective in the field of construction related sustainability, namely the often unseen or overlooked topic of site works and landscaping related carbon/climate impacts. The goal is to underline the importance of further research, and thereby to contribute towards improved design solutions. Although our focus here is to draw attention to a little researched “problem”, not solutions, we are very engaged in design solutions too. At the suggestion of another reviewer who feels this is lacking, we have added a new section 8 outlining some key pointers towards solutions – connecting this to the paper by relating them to our four specified areas of urban design, materials, life cycle and climatic context. This helps to “tie the pieces together”, adding brief conclusions to follow up these four areas noted. Please see page 16 lines 603 – 608.

 

6. The results are not supported with sufficient method and materials.

• Reply: Thank you for your comment. We consider the methods sufficient but recognise that the case data presented here is limited. However, full LCA and EC analysis of a large urban development (such as the one China source cited) is an extremely large and demanding task, well beyond our scope. It would also require an extremely long paper. Our topic is however original and of considerable importance for sustainable construction and needs to be published. We submit that not least with the corroborating support of the data and experience from the wide research literature base used, the analyses whilst simplified are sufficiently robust.

Author Response File: Author Response.docx

Reviewer 4 Report

Comments and Suggestions for Authors

The problem of carbon footprint research is acute. There is a debate in the world about the causes and consequences of the carbon footprint, which could be addressed in the article.

Considering the problem of carbon footprint and its reduction from the point of view of construction is a popular solution. The article is devoted to this issue. As a result of reading the article, there was no sense of holistic research. Motivation, tasks, and methods are unclear. In the case of a clear formulation of goals, objectives, approaches to solving, and a better presentation of the results, the article may be interesting. The article provides good reviews of existing solutions.

Recommendations:

1) I recommend changing or removing the first two sentences of the abstract. They do not carry any semantic meaning.

2) Lines 52, 57 – the design of the links does not comply with the recommendations, check here and further

3) "Among these, transport and on-site impacts are normally of the order 56 of a few per cent only"

It is unclear what the authors mean. I recommend correcting the discussion of the scheme and providing statistics for all operations.

4) 12 links to represent the situation in the world on the issue under discussion is very few. The introduction should be reworked. Also, it's not clear from the introduction what the problem is? What is the solution? What is the purpose of the work? I recommend to add all these aspects to the introduction.

5) "In dense cities, even apparently "green" areas between tall buildings often consist only of a thin green layer that covers extensive engineering works such as underground 102 parking and infrastructure..."

I recommend adding illustrations or diagrams.

6)  The abbreviations AE and OE are given on lines 35-36. Why are they listed in section 3 again.

7) Table 2. What does the number 1 in the title mean?

8) From the article incomprehensible methods used in the work. It is difficult to assess the quality of the conducted research. The work is more like a Review article.

9) The conclusions are very stingy and do not follow from the results, since it is unclear what is the result, what is a citation and a review.

Author Response

Review #4:

The problem of carbon footprint research is acute. There is a debate in the world about the causes and consequences of the carbon footprint, which could be addressed in the article.

Considering the problem of carbon footprint and its reduction from the point of view of construction is a popular solution. The article is devoted to this issue. As a result of reading the article, there was no sense of holistic research. Motivation, tasks, and methods are unclear. In the case of a clear formulation of goals, objectives, approaches to solving, and a better presentation of the results, the article may be interesting. The article provides good reviews of existing solutions.

• Reply: We acknowledge this comment and have modified the text in order to better express the goals, objectives, approaches. The major goal has been to identify and illustrate, with simple case analyses, a relatively new and original perspective in the field of construction related sustainability, namely the often unseen or overlooked topic of site works and landscaping related carbon/climate impacts. The goal is to underline the importance of further research, and thereby to contribute towards improved design solutions.

Recommendations:

• I recommend changing or removing the first two sentences of the abstract. They do not carry any semantic meaning.
• Reply: Thank you for your suggestion. We have modified this; page 1 lines 4 – 30.
• Lines 52, 57 – the design of the links does not comply with the recommendations, check here and further
• Reply: Thank you for your comment. All references have been double checked and the errors have been solved.
• "Among these, transport and on-site impacts are normally of the order 56 of a few per cent only"

It is unclear what the authors mean. I recommend correcting the discussion of the scheme and providing statistics for all operations.

• Reply: Thank you for your comment. Apologies, references were named instead of numbered, and two were missing. These two, Peng and Hafez, are the sources for transport and on site EC and like other sources, indicate figures of from 2 to 6% of the total lifecycle EC.
• 12 links to represent the situation in the world on the issue under discussion is very few. The introduction should be reworked. Also, it's not clear from the introduction what the problem is? What is the solution? What is the purpose of the work? I recommend to add all these aspects to the introduction.
• Reply: Thank you for your comment. We recognise that many more links to this knowledge could be given but feel that they are well known and for brevity’s sake not necessary here.
• "In dense cities, even apparently "green" areas between tall buildings often consist only of a thin green layer that covers extensive engineering works such as underground 102 parking and infrastructure..."

I recommend adding illustrations or diagrams.

• Reply: Thank you for your comment. The figure 3 illustrates this. The whole surface area seen is in fact covering underground parking. So, we have added this information to the text for clarity.
• The abbreviations AE and OE are given on lines 35-36. Why are they listed in section 3 again.
• Reply: Thank you for your suggestion. It has been removed from section 3.
• Table 2. What does the number 1 in the title mean?
• Reply: Thank you for your comment. The table has been revised; page 9 lines 349 – 350.
• From the article incomprehensible methods used in the work. It is difficult to assess the quality of the conducted research. The work is more like a Review article.
• Reply: Thank you for your comment. We have now in section 4, discussed more about the methods and calculation tools employed in our case studies. We have also added a note that the data in case 3 was only studied for comparative purposes, to verify/solidify the findings of our major case 2, and is therefore not presented in detail. The LCA scope – in our case broadly cradle to cradle – is now briefly noted. The development of the construction data is also described a little more however with the same underlined point that we have intentionally put together a simplified data picture corresponding to the major EC factors. Quantities are from design documents and drawings (cases 1 and 3) and in addition BoQs and site visits (case 2) on the methods and databases used. Please see page 5 lines 182 – 187.
• The conclusions are very stingy and do not follow from the results, since it is unclear what is the result, what is a citation and a review.
• Reply: We acknowledge this comment and have modified the text in order to better express the conclusions. Although our focus here is to draw attention to a little researched “problem”, not solutions, we are very engaged in design solutions too, and on the suggestion of reviewer, have therefore added a new brief section 8 outlining some key pointers towards solutions – connecting this to the paper by relating them to our four specified areas of urban design, materials, life cycle and climatic context. This helps to “tie the pieces together”, adding brief pointers (hardly conclusions) to follow up the four areas noted. Please see page 15 line 542 to page 16 line 607.

Author Response File: Author Response.docx

Reviewer 5 Report

Comments and Suggestions for Authors

The article introduces a comparative study of the embodied carbon (EC) impact of site works and infrastructures (surface and underground) related to three building developments, as a percentage of the total EC of the whole interventions. The topic is very intriguing, since it investigates an issue widely overlooked in research works on the carbon impacts in the building sector, generally focusing only on the embodied carbon of buildings. Due to its implications on the urban context, the topic is relevant for the journal’s scope.

Although the work does not formally feature all the sections that are typical of a research article (‘Literature review’, ‘Materials and Methods’, ‘Results’), the text is well organized and addresses several substantial and contextual aspects. Nevertheless, some points can be found that should be improved.

One first point is the engagement with bibliographic sources. Many of the bibliographic references are quite dated; my suggestion is that more works from the last 5 years should be included.

As for the contents, some ambiguity should be addressed; in particular, the foundations for the statements about the future trend of the impacts’ relative weight should be strengthened. In Section 7.2 the Authors state that cements and steel prominently account for significant EC shares, and that they are often used for both buildings and underground or site works, then the proportion of EC in site works may change little as both buildings and the site works employ similar materials and technical advances (Lines 434-438). It would be then appropriate to further describe those features that, on the contrary, make relative weights different and can thus allow a decrease of the EC portion linked to infrastructures and site works, which the article mainly aims to promote.

As for data used, in Table 1 the “Building Type” column is heterogeneous, as it alternatively indicates the building’s use (‘Residential’, ‘Office’, ‘Commercial’), the energy performance level (‘low energy’, ‘NZEB’), or height (‘low-rise’); this should be made homogeneous.

With respect to the EC calculations in the case studies, the article only mentions the source (NCMA-TEK), that is not appropriately referenced in the bibliographic base nor described in the text. More deepening and details should be given in the text, in particular the basic assumptions or approximations and validity boundaries of the database (if any) used to determine the EC values.

Still more important is to consider that in a comparative study, the cases should be processed and described on a homogeneous basis. In the proposed article, the three case studies present, instead, quantitative descriptions with different detail levels (the third one even gives only the final percentage -28%- without further information: how was it obtained?). Such points should be adequately addressed and better reported, in order to improve the scientific rigorousness of the work.

One last issue relates to the discussion of results; for the article to be fully relevant for the journal’s scope, planning implications should represent the most relevant and thorough part of the section, whilst they are too briefly addressed; my suggestion is to delve more into that in the analysis of results, summarizing the main outcomes in the Conclusions section, together with the limitations of the study.

Comments on the Quality of English Language

The English language is adequate and understandable overall; a final English proofreading could anyway improve the general fluidity of the text.

Author Response

Review #5          

The article introduces a comparative study of the embodied carbon (EC) impact of site works and infrastructures (surface and underground) related to three building developments, as a percentage of the total EC of the whole interventions. The topic is very intriguing, since it investigates an issue widely overlooked in research works on the carbon impacts in the building sector, generally focusing only on the embodied carbon of buildings. Due to its implications on the urban context, the topic is relevant for the journal’s scope.

Although the work does not formally feature all the sections that are typical of a research article (‘Literature review’, ‘Materials and Methods’, ‘Results’), the text is well organized and addresses several substantial and contextual aspects. Nevertheless, some points can be found that should be improved.

One first point is the engagement with bibliographic sources. Many of the bibliographic references are quite dated; my suggestion is that more works from the last 5 years should be included.

As for the contents, some ambiguity should be addressed; in particular, the foundations for the statements about the future trend of the impacts’ relative weight should be strengthened. In Section 7.2 the Authors state that cements and steel prominently account for significant EC shares, and that they are often used for both buildings and underground or site works, then the proportion of EC in site works may change little as both buildings and the site works employ similar materials and technical advances (Lines 434-438). It would be then appropriate to further describe those features that, on the contrary, make relative weights different and can thus allow a decrease of the EC portion linked to infrastructures and site works, which the article mainly aims to promote.

As for data used, in Table 1 the “Building Type” column is heterogeneous, as it alternatively indicates the building’s use (‘Residential’, ‘Office’, ‘Commercial’), the energy performance level (‘low energy’, ‘NZEB’), or height (‘low-rise’); this should be made homogeneous.

With respect to the EC calculations in the case studies, the article only mentions the source (NCMA-TEK), that is not appropriately referenced in the bibliographic base nor described in the text. More deepening and details should be given in the text, in particular the basic assumptions or approximations and validity boundaries of the database (if any) used to determine the EC values.

Still more important is to consider that in a comparative study, the cases should be processed and described on a homogeneous basis. In the proposed article, the three case studies present, instead, quantitative descriptions with different detail levels (the third one even gives only the final percentage -28%- without further information: how was it obtained?). Such points should be adequately addressed and better reported, in order to improve the scientific rigorousness of the work.

One last issue relates to the discussion of results; for the article to be fully relevant for the journal’s scope, planning implications should represent the most relevant and thorough part of the section, whilst they are too briefly addressed; my suggestion is to delve more into that in the analysis of results, summarizing the main outcomes in the Conclusions section, together with the limitations of the study.

 

• Reply:

1. Thank you for your comment. We have added some updated sources, although it has been a point by also referring to older ones that the overall thrust of these figures has been quite well established for some time, back to the early 2000s.
2. Although our focus here is to draw attention to a little researched “problem”, not solutions, we are very engaged in design solutions too, and on the suggestion reviewers, have therefore added a new brief section 8 outlining some key pointers towards solutions – connecting this to the paper by relating them to our four specified areas of urban design, materials, life cycle and climatic context. This helps to “tie the pieces together”, adding brief pointers (hardly conclusions) to follow up the four areas noted. This takes up your comment about what other materials and approaches can reduce the EC. However please accept that a fuller discussion of design and construction strategies lies well beyond the scope of this paper. A follow-up paper with that focus might be useful. Please see page 15 line 542 to page 16 line 602.
3. NCMA-Text has been edited and correctly referenced now; Please see page 8 lines 341 – 342. In addition, databases employed are principally ICE and OneClick and the figures are also cross checked with various other EC figures as indicated in our tables. Calculations are in all cases our own.
4. As you note the tables include a heterogeneous sample of buildings. This is intentional, to illustrate how the figures involved largely fall into the same areas, then broadly summarized as basis for our case study discussions. There would naturally be much use in (a different task!) analysing where the differences lie in, say, “heavy” buildings which range from around 500 to well over the double. When one gets down to very low figures, then indeed some apparently quite minor building components can make a big difference – rather as the case of energy in passivhaus type buildings, where even small thermal bridges become significant.
5. Regarding your correct comment about case study 3, we have added a note that the data in case 3 was only calculated and studied for comparative purposes, in particular to verify/solidify the findings of our major case 2, and is therefore not presented in detail. Please see page 11 lines 421 – 422.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have revised the paper according to the comments. No further comments are needed.

Author Response

There is no more comment from this reviewer

Reviewer 4 Report

Comments and Suggestions for Authors

It is fine now, thank You

Author Response

There is no new comments from this reviewer