Low Carbon Emissions and Energy Consumption: A Targeted Approach Based on the Life Cycle Assessment of a District

1.       Title: Maybe LCA can be included in the title to highlight the method applied in the paper.

Response1.

 The title of the manuscript has been updated:

“Low Carbon Emissions and Energy Consumption, a Targeted Approach Based on the Life Cycle Assessment of a District”

2.       Abstract: Too many unclear statements. Abstract should be stand-alone; all terms or sentences should be clear. E.g., ‘It is strongly preferable to densify the neighbourhood vertically rather than horizontally and rainwater harvesting systems were more effective than permeable soils’. What does it mean by vertically or horizontally? Readers would not know without reading the paper first. And ‘more effective’ in what aspect? Why rainwater harvesting system and permeable soils were compared? Is there any other systems considered? Please revise the abstract.

Response2.

The Abstract has been improved

“Nowadays, the methodology aiming to achieve carbon neutrality and net zero energy on a large scale is known. Despite this, few specialists are mastering this technology in the world, so, how should be proposed a common method for all the nations at the district scale? In addition, a lack of massive, regular, and consistent data on carbon emissions and energy consumption has made it significantly difficult to understand the origins of climate change at the building and neighbourhood scales. This work has as its main goal to assess the different strategies that allow for to reduction of the concentration of CO₂ and energy demand at the district level. The life cycle assessment of a new district has been carried out over 100 years during the four stages of the life cycle of the neighbourhood (construction, operational, demolition and end of life). The results showed that up to 93% of greenhouse gas (GHG) was produced during the operational stage. The energy demand due to transport and waste management during the use phase is 60% of the total energy demand of the district over its entire life cycle. “

3.  HVAC abbreviation on Page 2 has not been defined. DHW is defined only on Page 20+ even though it starts to appear in the paper on Page 10. Please make sure all abbreviations are defined at their first mention/appearance in the paper.

Response3.

HVAC abbreviation has been defined. DHW is defined at the first time used.

All abbreviations are defined at their first mention/appearance in the paper.

4.       Literature review should be extended mainly to review existing studies that have used LCA at building and neighbourhood scale to show the research gap from these studies that you want to address in this paper. After that you should connect the gap with the novelty of the paper.

Response4

A literature review has been added

Stephan et al. [27] demonstrated that energy consumption during the operational phase is the main contributor to environmental impacts over the complete life cycle of a district. Indeed, it accounts for nearly 40% of primary energy consumption (PEC) or for more than 42% of greenhouse gas emissions (GHG). However, at the neighbourhood scale, the dominance of the use phase appears less predominant compared to the other phases. In addition, the study of Nichols and Kockelman [28] relating to the analysis of four districts, reveals a score of 53% of the PECs coming from construction, 45.5% of the PECs coming from mobility (operational consumption and embodied energy of infrastructures) and only 1% from other public infrastructure (water, wastewater and lighting). By comparing several urban developments of different densities, Norman et al. [29] conclude that mobility contributes much more significantly to the total energy consumed and to GHG emissions in the case of low-density urban development than in the case of dense development. Thus, the share of impacts due to buildings is relatively greater in the case of high density. On the other hand, comparing four scenarios, based on different types of residential buildings, Trigaux et al. [30], showed that the contribution of road infrastructures accounts for 1% to 6% of the total impacts. When looking at studies of neighbourhoods with low energy consumption, without taking mobility into account, Herfray et al. [31], show respectively that in terms of primary energy consumption, the construction phase matters for 7% and 13.5%, the operational phase for 92% and 85% and the deconstruction phase for 1% and 1.5%. Once again, we note the predominance of the operational phase and the weak contribution of the construction and deconstruction phases. Peuportier et al. [32], emphasize the fact that architecture also strongly influences performance. With identical technical characteristics, the consumption simulated by the EQUER software varies from simple to triple between two buildings from the same district but in different blocks.

Thus, even if the heterogeneity of the studies does not allow to draw general conclusions, trends can be noticed.

All these studies are conducted in old buildings and old neighbourhoods. There is little research focused on environmental impact study cases from new neighbourhoods more suited to new climates. A high concentration of research carried out in these types of neighbourhoods would easily make it possible to propose a standard for all countries. Hence the importance of this study.

5.       Page 5: ‘Once these few data have been entered’ entered where? How the model was obtained is not clearly explained. Please also explain why this model is required for the LCA study.

Response 5.

After having written these data into the modeller interface –plead, it is now time to model our neighbourhood in three dimensions.

The model of the district is not invented, the drawing is drawn from a district actually existing in Belgium. With the architectural plan of this district provided by its designers in an AutoCad file, we have represented this district in the pleaides software.

6.       Page 6: All the assumptions in the second paragraph should be justified or the sources of where the values were taken should be cited.

Response 6.

All the sources have been cited in the revised manuscript

7.       Page 6: ‘the environmental data used for the assessment of the two studied environmental impacts were collected’ the two assessed environmental impacts should be specified here, not at the end of the paragraph

Response 7.

Page 6 has been updated

8.       The authors use too many sub sub sections, some of which have only 2 – 3 lines of sentences. If possible combine those related subsections together.

Response 8

The percentage of Sub sub –section has been significantly reduced.

9.       Section 3.5.2: I don’t think this section to explain the Pleiades software is necessary. It should be removed and just cite the source that the readers can refer to know more about the software.

Response 9.

Section 3.5.2. has been significantly reduced

10.   Pages 10, 11, 12: The same comment as point 6, justify or cite the source for all the assumptions.

Response 10

The source has been added for each hypothesis pages 10, 11 and 12

11.   Page 10: What are the abbreviations under Table 3 for? They did not appear in the table and seems out of place there.

Response 11.

This mistake has been corrected, thanks

12.   Page 11: The unit for water capacity is l? should not it be written as L?

Response12.

This mistake has been corrected, thanks

13.   Please check the consistency of the font size. There are some paragraphs with obviously different font size, e.g., on Page 11 and 12.

Response13.

This mistake has been corrected in all the manuscript, thanks.

All the paragraphs have the same size

14.   Page 11: ‘The results for the ten buildings’ what are the 10 buildings? A3 and? They have not been described previously.

Response14.

The neighbourhood studied consists of 10 named buildings (from A1 to A10), as shown in figure 2

15.   What is initial scenario? Needs to be explained together with the different design scenarios considered before you discuss the results of each scenario.

Response15.

The initial scenario makes it possible to describe the current state of the neighbourhood with real and existing information, without fixed assumptions, as described in the methodology section and in this video: https://www.youtube.com/watch?v=V9b0DwzDQS8

Comments

Response

1. In the introduction, it is suggested to further clarify the innovation of this paper in terms of research perspective and research ideas and contents.

Response1

The introduction section has been updated in terms of research perspective and research ideas and contents.

2. In the references, it is suggested to increase the references to the literature of the last five years to at least 50% of the total literature.

Response2

The reference section has been updated with recent sources. Most of the recent references have been added.

3. it is recommended to place the limitations of this paper in the conclusion of Part VI in Part V. In other words, separate the conclusions from the limitations of this paper.

Response3

Limitations section has moved to the conclusion section as recommended

Comments on the Quality of English Language

The paper flows well in general, with some adjustments to the order of words and grammar in some places to make it flow better .

Response4

The english language has been revised in the entire manuscript

Comment 1: The abstract should contain the background to the study, the methodology, the content of the study and the conclusions of the study. However, the research context of this manuscript does not lead well to the research questions, and the research conclusions should focus on innovative findings.

Response 1

Abstract has been revised under the basis of this recommendation

Nowadays, the methodology aiming to achieve carbon neutrality and net zero energy on a large scale is known. Despite this, few specialists are mastering this technology in the world. What new scenarios applied at the neighbourhood scale generate a significant reduction in the rate of CO₂ emissions and energy demand? In addition, a lack of massive, regular, and consistent data on carbon emissions and energy consumption has made it significantly difficult to understand the origins of climate change at the building and neighbourhood scales. This work has as its main goal to assess the different strategies that allow for to reduction of the concentration of CO₂ and energy demand at the district level. The life cycle assessment of a new district has been carried out over 100 years during the four stages of the life cycle of the neighbourhood (construction, operational, demolition and end of life). The results showed that up to 93% of greenhouse gas (GHG) was produced during the operational stage. The energy demand due to transport and waste management during the use phase is 60% of the total energy demand of the district over its entire life cycle. There is still a possibility to maintain air temperature growth around 1.5°C in the next decade by combining: (Global warming + 100% of heavy renovation of all buildings + 100% of electric car – renewable energy). This strategy allows to reduce over 92% of CO₂ produced at the district level.

Comment 2: Keywords are words that summarise the main content of an article, but the key words in this manuscript do not summarise the research content very well. For example, '2050'.

Response 2.

The list of Keywords has been improved

Low carbon; energy demand; neighbourhood; climate change; Life Cycle Assessment

Comment 3: The quotation introduces the context of the study and many of the statements do not indicate their source. For example, "This objective is also defined in the Paris agreement signed by 195 countries, including the European Union."

Response 3

The Introduction has been adjusted by  numerous sources

Comment 4: sections of Introduction. The background of carbon emissions seems too simple. There has already been a large amount of literatures discussing this topic. There is a need to better elaborate the background. Please consider citing following papers:enttiled "Revisiting the environmental kuznets curve hypothesis in 208 counties: The roles of trade openness, human capital, renewable energy and natural resource rent", and entitlted "Does urbanization redefine the environmental Kuznets curve? An empirical analysis of 134 Countries"

Response 4

We improved the introduction by adding some studies related to Life Cycle Assessment. And also, we added these new research recommendations.

An example of reference added

 Achieving carbon neutrality requires a comprehensive understanding of the effect of various key factors on carbon emissions to this end, Qiang Wang et al. [52] conducted a study to examine the effect of trade openness, capital human, renewable energy and natural resource rent on carbon emissions under the environmental Kuznets curve (EKC) hypothesis. They found that the natural resource rents increase carbon emissions in most countries.

Comment 5: Section 3.1 describes the research sample chosen for this manuscript, but does not elaborate on the typicality of the research sample. It is recommended that the authors make changes and improvements to this.

Response 5

The typicality of the research sample are described in section 3 reserved to the methodology.

Comment 6: What is the specific meaning that Figure 1 is trying to convey? It is recommended that this be removed if it is not necessary. Also, for the source of the image, it is necessary to make a note of the source of the data below the image.

Response 6

Figure 1 shows a 3D view of the neighbourhood studied.

The source has been added

Comment 7: The format of this manuscript needs to be further standardised. For example, the format of the title in 4.6 is clearly different from the format of the other titles.

Response 7

The format has been standardized in all the manuscript

Comment 8: The formatting of the fonts in Figures 7 - 11 does not show the content of the images very clearly and it is recommended that the authors make adjustments to the formatting of all the images in the manuscript.

Response 8

All the figures have been improved

Comments on the Quality of English Language

Response 9

English style has been revised in this manuscript

Questions

Responses

1.   Please replace the comma in the title with a colon (:).

1. Has been done

 2.       All ambiguities have been removed from the abstract, but please revise the second last sentence ‘There is still a possibility to maintain air temperature growth around 1.5°C in the next decade by combining: (Global warming + 100% of heavy renovation of all buildings + 100% of electric car – renewable energy)’, to remove the colon and bracket by describing the proposed solution in a full sentence.

2. There is still a possibility to maintain air temperature growth around 1.5°C in the next decade by combining: Global warming + 100% of heavy renovation of all buildings + 100% of electric car – renewable energy. This strategy allows to reduce over 92% of CO₂ produced at the district level.

3.       Refer to my comment #15: The link for the video is not necessary, just mention where the description of the initial scenario can be found (from which section of the methodology in the paper or cite the source appropriately, please check the citation format for video if any). 

3. The initial scenario is describe in section 3.7