Study on Carbon Emissions from the Renovation of Old Residential Areas in Cold Regions of China
Round 1
Reviewer 1 Report
The article proposes a topic of great interest with the aim of analyzing CO2 emissions in the renovation process of old residential areas. It presents the case study of a specific building and focuses the analysis on the stages of materialization and use after renovation, comparing the new emissions with those of the building in its previous state.
In the construction process, sections such as CO2 emissions caused by construction waste (transport, recycling, or disposal), the efficiency of the building's machinery (pumps, boilers, fans, heat pumps if any, radiators, etc.), or the consumption and emissions derived from the time of execution of the renovation are forgotten. This is due to the fact that the chosen building is simple in its volumetric configuration, construction, and installations. It would have been desirable to choose a more complex example, in order to take into account all the elements, actions and consumption involved in the generation of residential CO2. Immediate consequences of this are: the graphical information of the building is scarce because only axonometric and small and anodyne details of the constructive changes included in the building renovation are presented (page 7); the methodology (pages 3-5) is excessively elementary in formulas and the case study (pages 5-10) is simply a tidy and basic data summation exercise.
Applicability is limited to single, isolated residential units only. The conclusions cannot be extended to residential areas, because there are other sources of co2 emissions to be taken into account (presence of vehicles, percentage of trees, porous pavements, type of artificial lighting,) of urban nature.
Although the bibliography and the state of the question presented are interesting and extensive, the depth of the work is more typical of undergraduate research and does not reach the levels of specificity and scientific complexity desirable for the journal.
Comments for author File: 
Comments.pdf
Author Response
Dear reviewer,
We thank the reviewer for your time in providing a review of our manuscript. Because only one attachment can be uploaded, we put the response and manuscript in one file.
Please see the attachment.
If you have any questions, please let me know.
Kind regards,
Mr. He Yi
Author Response File: Author Response.pdf
Reviewer 2 Report
The objective of this study is to quantify the carbon emissions of retrofitting old residential building areas in cold regions of China. Based on a case study building from Ji´nan city, the study estimates carbon emissions from building product manufacturing, through useful life operation and end-of-life disposal. Although the analysis presented suggests that there may be some relevant and useful findings for publishing in this journal important amendments have to be made to improve the communication of the article. The Introduction section requires to be contextualized on a broader perspective to give an idea of the relevance of China´s building sector with regards to the global environmental crisis and discuss later the numerical results of previous work in China or elsewhere in terms of carbon and energy intensity so that comparisons could be made. The Methodology section is too fragmented with too many definitions and equations that make it difficult to read. Given the “emission-factor approach” adopted, priority should be given to describing the main data sources employed (GB/T 51366-2019 standard or other relevant). It is not clear why the chosen building of Ji´nan city is representative or, at least, relevant to the purposes of the study, this should be stated explicitly. A Result section should be included, since as it is now it is not clear at which point the Methodology section ends and starts the description of the actual results of the study. Besides, it is desirable, given the extensive analytical work presented in the article, to include a Discussion section to expand the interpretation of results, remark key findings, and state their implications on a broader perspective such as on old residential building areas in China or elsewhere. |
Title: this must be proofread; it may be better instead of using “of Renovation” to use “from Renovation” and somehow clarify that the analysis was performed on buildings, and, definitively, indicate that was performed for “Cold Regions of China”
Abstract, Line 17: it is not clear what it means here the word renovation, it should be a more specific (renovation of buildings? Shouldn’t be retrofitting of buildings?)
Abstract, Line 18: the term “object of study” should be better referred as “case study” or “case study building.
Introduction, Line 50: a breakdown of all residential energy end uses should be included given those included in the analysis: electricity, heating (does this include cooking?) and cooling.
Introduction, Lines 54-95: this paragraph is way too long, this should be divided into at least two if not three.
Methodology, Lines 128-135: This paragraph should clearly state the stages that were excluded from the lifecycle analysis and why.
Methodology, Line 134: instead of “carbon emissions for buildings” it should be “carbon emissions of buildings”.
Methodology, Line 147: it is not clear the use of numeration (1 to 3), to what does each number refers? it is too fragmented to follow the reading.
Methodology, Line 165: why the carbon source/sink was ignored? This should be clearly stated.
Methodology, Line 166: does heating only refers to space conditioning or also includes hot water?
Case study, Line 197: in this section it should be argued how does the case study building relates to the whole residential building stock (does it have representative features?) and to what extent is it representative, or not, and why was selected for studying
Case study, Line 208-212: further details should be given for the simulation analysis performed: was this performed as single zones? What was the thermostat setting? 24 hours turned on? Why were the stated thermostat values chosen? How was occupation assumed within the buildings? How many dwelling units are comprised in the resulting values?
Case study, Line 220-226: heating and cooling loads should also be given in kWh/m2 per dwelling as reference values for comparisons.
Case study, Table 2: it will be clearer for comparisons to show al results under the same units, that is all in kWh.
Carbon increment static payback period, Line 338: square meters “m2” should be written as a superscript “m2”, this mistake is repeated in other parts of the text.
General suggestion: there are too many tables that could be summarised into graphs which allows a better judgement of the results, and some time the reading gets confusing.
Author Response
Dear reviewer,
We thank the reviewer for your time in providing a review of our manuscript. Because only one attachment can be uploaded, we put the response and manuscript in one file.
Please see the attachment.
If you have any questions, please let me know.
Kind regards,
Mr. He Yi
Author Response File: Author Response.pdf
Reviewer 3 Report
There are certainly technical issues that need to be resolved. Here are listed only some of them:
no space between the number and the unit in physical quantities. For example,
Lines 145 and 146 have no space between kg and CO2.
Lines 194 and 195 are too small fonts.
Lines 220 etc. and Table 2 there is again no space t and CO2.
Lines 248-250 there are missing interpunctions.
From line 283 the same comment regarding space as above: tCO2, kgCO2 and at many other places.
Figure 3 has no weight (it is irrelevant) for this kind of paper, please, remove it as important numbers are already written in the text above.
It would be good to see the properties of the current building considering all building elements as you have done after renovation. I would suggest the table so one can see what was before (where from come the U/values you mention), and then what has been improved with the renovations.
Also, you do not mention where from you get reference values U/vaules that you aim to achieve after renovation.
How about the ventilation system? ventilation and infiltration are not mentioned at all nor is the impact on the CO2 emissions. It is well known that this kind of heat loss might mi significant. Have you taken it into account but haven't mentioned it???
What is with the alternative energy sources? What are they not considered and mentioned only as the possibility for improvement?
Author Response
Dear reviewer,
We thank the reviewer for your time in providing a review of our manuscript. Because only one attachment can be uploaded, we put the response and manuscript in one file.
Please see the attachment.
If you have any questions, please let me know.
Kind regards,
Mr. He Yi
Author Response File: Author Response.pdf
Reviewer 4 Report
The authors quantify the carbon emission or carbon increment of various renovation measures for a single building in an old residential area. The results are significant if taken as an examination methodology, but assume little relevance due to the difficulty of generalizing them to different contexts or to buildings of the same climatic and constructive context. A single building does not represent a significant sample.
There are some corrections to be made in the text and a careful rereading of the text should be done to give greater readability.
1) For better clarity, in equation (7) a parenthesis should be used and "y" should be put outside it
2) There is something wrong in equation (8): DE should be just the part in parenthesis Eop-E’op
3) After equation (9) should be pointed out: <<…Cre is the carbon emission intensity of building renovation per unit area “spread over the expected years of use remaining”;…>>
4) In eq (10) Ein (is clear but) is not defined anywhere in the paper
5) What did the authors mean for “5-story residential building” at line 200?
6) Please in table 3 use always the same unit kgCO2/xx and not kgCO2e/xx
7) At line 68/69: "There are many approaches to calculating carbon emissions in carbon emission calculations,...." could be improved in "There are many approaches to calculate carbon emissions,..."
Author Response
Dear reviewer,
We thank the reviewer for your time in providing a review of our manuscript. Because only one attachment can be uploaded, we put the response and manuscript in one file.
Please see the attachment.
If you have any questions, please let me know.
Kind regards,
Mr. He Yi
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The article proposes a topic of great interest with the aim of analyzing CO2 emissions
in the renovation process of old residential areas. It presents the case study of a
specific building and focuses the analysis on the stages of materialization and use after
renovation, comparing the new emissions with those of the building in its previous
state.
The review proposed by the authors, after the first report on the article received, is acknowledged and appreciated. In relation to their responses, the following can be said:
Response 1:
The authors refer to the influence of the Khrushchyovka model on the type of block chosen for their study. It would be desirable to elaborate on this point, and to describe in more depth the urbanistic, typological, form and volume, interior layout and material characteristics of this model of residential building. In parallel, they could include examples of rehabilitation of the same nature carried out in other countries, such as Russia, Slovakia, Belarus and the Czech Republic, where the Khrushchyovka block and later ones such as the Brezhnevkas are undergoing the same operations proposed by the study.
Response 2:
Again, the importance of the quality of the graphics that should accompany the article is stressed, being essential data such as a better description of the constructive sections of walls and roofs, technical characteristics of joinery and doors, floor slabs, foundations, thermal bridges.
Response 3:
Although the authors explain that they follow the Standard for Building Carbon Emission Calculation. 2019, GB/T 51366-2019, this does not mean that they can propose improvements in the procedure, as Yingjie Chen , Yunfeng Wu, Ning Chen, Chaofeng Kang, Jiabin Du and Cheng Luo do in the article `Calculation of Energy Consumption and Carbon Emissions in the Construction Stage of Large Public Buildings and an Analysis of Influencing Factors Based on an Improved STIRPAT Model'. This involves, for example, introducing new CO2 consumptions not taken into account in the renovation process by the Standard, such as those produced by demolition, waste and transport to landfill originating during construction, energy consumed by small machinery,...
Response 4:
The reply to point 4 is considered appropriate.
Comments for author File: Comments.pdf
Author Response
Dear reviewer,
We thank the reviewer for your time in providing a review of our manuscript. We are glad of the reviewer’s generally positive assessment of our manuscript and will provide responses to each individual point below. For clarity, we put the responses and the manuscript into one PDF, and the content is modified in RED in the manuscript.
Best wishes
Yi He
Author Response File: Author Response.pdf
Reviewer 2 Report
The authors have adressed all the raised issues satisfactorily.
Author Response
Thank you for your comments.
Round 3
Reviewer 1 Report
The reviewer accepts the paper in this form
