An Integrated Multi-Objective Optimization Framework for Environmental Performance: Sunlight, View, and Privacy in a High-Density Residential Complex in Seoul

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this study, a multi-objective optimization framework targeting three key aspects of residential environment —daylight access, visual openness, and ground-level privacy — was established and applied to practical cases. The research is interesting, and my main comments are as follows:

• The abstract is too long, and there is no need to introduce the specific details of the research in the abstract. It should be further condensed.
• Why choose the third phase of Helio City complex as a case study, and does it have representative components.
• The three parts of Chapter 5 should be written separately, as they are not all conclusions of the research. Section 5.1 is more like Results and Discussion, while Section 5.3 should be included as a separate chapter.

Author Response

 

Comment 1: The abstract is too long and should be condensed

Response: We have significantly condensed the abstract from over 400 words to approximately 180 words, focusing on key findings rather than methodological details. The revised abstract now clearly presents the research objectives, main methodology, key results, and implications without excessive detail.

Comment 2: Why choose the third phase of Helio City complex as a case study?

Response: We have added a clear explanation in Section 1.2 (marked in red) stating three critical reasons for selecting Helio City Phase 3:

• First, it represents a typical high-density reconstruction project common in Seoul's urban redevelopment
• Second, its location at the complex's northern edge, surrounded by other phases, creates the most challenging environmental conditions, making it an ideal test case
• Third, with 2,026 units across 18 buildings of varying heights (13-35 floors), it provides sufficient complexity for comprehensive performance evaluation

Comment 3: Chapter 5 structure should be reorganized

Response: We have restructured the chapters as suggested. Section 5.1 (comparison results) has been moved to Chapter 4.4 as "Results and Discussion." Chapter 5 now focuses on conclusions and broader implications, while limitations have been separated into Chapter 6.

Additional Improvements Made

Beyond the specific reviewer comments, we have also:

• Added comparative analysis with previous studies (Table 18)
• Improved the logical flow between sections
• Enhanced technical clarity throughout
• Ensured consistency in terminology
• Updated all references to maintain proper numbering sequence

We believe these comprehensive revisions have significantly strengthened the manuscript and addressed all reviewer concerns. We are grateful for the reviewers' insightful comments that have helped improve the quality and clarity of our research.

Thank you for considering our revised manuscript.

 

Reviewer 2 Report

Comments and Suggestions for Authors

This is an interesting and well-executed research work. The sequential multi-objective optimization framework is well-structured and innovative, integrating three crucial aspects of the residential environment. The quantitative approach through computational tools (Ladybug, Galapagos) and precise metrics provides objective and replicable results. Helio City represents a significant case study example for high-density urban planning.
The current study should better discuss the scalability and applicability to other contexts. While the Seoul case study demonstrates effectiveness in a specific high-density Asian urban context, several questions remain regarding broader implementation. Consider comparison with other optimized projects such as those in these papers:

https://doi.org/10.3390/aerospace12030229

https://doi.org/10.1016/j.scs.2025.106179

Author Response

Comment: Discuss scalability and applicability to other contexts

Response: We have added a comprehensive new section (5.2 "Generalizability and Broader Applications") that discusses:

• International applications with regional adaptations (tropical, European, North American contexts)
• Scalability from building clusters to district-level planning
• Integration with emerging technologies (ML, BIM, IoT)
• Applications for urban regeneration projects
• Evidence-based policy development support

We have also incorporated comparisons with recent optimization studies (Zhang et al., 2025; Di Loreto et al., 2025) as recommended, demonstrating how our modular approach differs from and complements existing methodologies.

Additional Improvements Made

Beyond the specific reviewer comments, we have also:

• Added comparative analysis with previous studies (Table 18)
• Improved the logical flow between sections
• Enhanced technical clarity throughout
• Ensured consistency in terminology
• Updated all references to maintain proper numbering sequence

We believe these comprehensive revisions have significantly strengthened the manuscript and addressed all reviewer concerns. We are grateful for the reviewers' insightful comments that have helped improve the quality and clarity of our research.

Thank you for considering our revised manuscript.

 

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Team,

The presented manuscript is thoroughly reviewed, and here are my comments targeting some aspects of the research to improve its quality before it can be published. 

It is suggested to add a clear statement of the study's objective and guiding research questions. 

Provide more support from literature, justifying the reasons for selecting some key decisions, such as selecting visual opening metrics, privacy thresholds, and core movement constraints. 

The research is heavily based on simulation without incorporating any form of post-occupancy data, user feedback, or stakeholder validation to confirm the practical implications of the proposed optimisations. 

It would be good to add some lines of critical analysis, discuss the impacts of your solution, like covering 20 ground floors on social, economic or functional impacts of such changes in public spaces. 

It is also suggested to benefit from a more balanced literature review, from recent international computational design and residential satisfaction analysis. 

In summary, this paper presented with high potential contribution to the field of performance-based urban housing design. 

Comments on the Quality of English Language

The manuscript would benefit from a careful language edit to improve clarity of explanation and flow of information. There are some parts with repetitive sentence structures that can distract from the main arguments. Some sentences are very long, which need attention, for example, lines 627 to 629. There are some parts which use awkward phrasing, like lines 158-159. 

Author Response

Comment 1: Add clear statement of study objectives and research questions

Response: We have added three explicit research questions and a primary objective statement at the end of Section 1.1 (marked in red):

1. How can multiple environmental performance criteria be systematically integrated into a unified optimization framework?
2. What are the trade-offs between sunlight access, visual openness, and privacy?
3. To what extent can algorithmic optimization improve environmental performance while maintaining development density?

Comment 2: Provide more literature support for key decisions

Response: We have strengthened literature support throughout:

• Added comprehensive explanation of Visual Openness Ratio methodology with Tables 5-6 and Figures 4-5
• Included privacy evaluation criteria based on Zheng et al. (2021) PVEI study with Table 8
• Added comparative analysis with Ahn et al. (2024) facade occlusion studies (Table 18)

Comment 3: Address lack of post-occupancy evaluation data

Response: We have added a dedicated paragraph in Chapter 6 (Limitations) acknowledging this critical limitation and proposing longitudinal POE studies for future research validation.

Comment 4: Discuss socio-economic impacts of converting ground floors to public spaces

Response: We have added a comprehensive discussion in Section 4.4 addressing:

• Creation of approximately 600m² of community spaces
• Potential for senior centers, childcare facilities, or retail spaces
• Possible increase in property values for remaining units
• Need for cost-benefit analysis considering lost residential revenue versus commercial income

Comment 5: Language improvements needed

Response: We have improved sentence clarity throughout the manuscript:

• Split long sentences (e.g., lines 627-629) into shorter, clearer statements
• Converted passive voice to active voice where appropriate
• Removed redundant adjectives and simplified complex phrases
  
  

  Additional Improvements Made

  Beyond the specific reviewer comments, we have also:

  • Added comparative analysis with previous studies (Table 18)
  • Improved the logical flow between sections
  • Enhanced technical clarity throughout
  • Ensured consistency in terminology
  • Updated all references to maintain proper numbering sequence

  We believe these comprehensive revisions have significantly strengthened the manuscript and addressed all reviewer concerns. We are grateful for the reviewers' insightful comments that have helped improve the quality and clarity of our research.

  Thank you for considering our revised manuscript.

Reviewer 4 Report

Comments and Suggestions for Authors

Thank you for the opportunity to review your interesting study identifying and then creating a methodology to optimise sunlight access, view quality and ground level privacy in a complex of apartment buildings. The paper is for the most part clear, well structured and easy to follow and makes interesting and well supported findings. In some places two reference systems have been used and the author date citations do not currently appear in the reference list which is in the square bracket format, this just requires checking throughout the article.

I have four main comments and a number of minor suggestions to improve the clarity of the article and to make its contribution to knowledge more explicit.

Main comments 

1. Lines 385-390: it would be helpful to provide some (possibly visual) examples of the visual openness ratio that is being proposed, perhaps when it is initially introduced higher up in section 2.4.2. For example, what would 100% view openness look like, and what is considered an appropriate or acceptable level of for this ratio 30%? 40%? 50%? This would help frame and support the statement that these levels require improvement.

2. Section 3.3: It is not entirely clear what is being proposed in this section and the link between shifting the core and view openness is not very explicit. Is the idea that middle and higher floors should be slightly offset from the ones below/above? If so how would this affect the structural integrity of the building, compliance with any building regulations and additional maintenance/weatherproofing/cost and material implications? If not please describe what is proposed more clearly.

3. Section 5.2: Please consider adding some consideration of how the process/framework that you have created could be applied in other scenarios and context to increase the impact of the research. For example how easy would it be for other researchers/developers to apply this at the design stage of other apartment complexes either in South Korea or internationally. This is especially important as the complex that has been studied is already extant so your optimisation is unlikely to be applied to this specific case study. 

4. Limitations section: Please add some discussion of the limitations of the work around the parameters selected and how in reality this optimisation would have to balanced with multiple other factors would also need to be taken into account such as cost, collaboration with residents associations in the design, overheating considerations etc. 

Minor points

Introduction: Maybe include an explanation of what floor area ratio is for readers who may not be familiar with this term.

Lines 114-125: This was a little confusing as I was reading it as a summary of how the article is structured and it actually seems to be how the research was structured. It might be worth adding a short paragraph on article structure below this to orient the reader. E.G. ‘In the rest of this article the literature is examined in section 2, the method is detailed in section 3, section 4 describes the results and the conclusions and implications are presented in section 5.’ or similar. 

Lines 138-15: It appears that two reference systems are being used here? There are numbers in square brackets and then name and date citations. The name and date citations probably need their own square bracket references after them to be consistent as is done the paragraph below. 

Figure 3: It might be helpful to increase the colour contrast between flat type and tower type buildings as the differentiation is not currently very clear. 

Lines 229-230: Please include a citation to Article 53 and Article 86. 

Lines 262-263: ‘Definition and calculation of the visual openness ratio.’ Please clarify if this is a sentence or a subheading. If a sentence please rephrase. 

Table 6: It is not entirely clear what the vertical vision grades relate to or measure. Please add a sentence to clarify this. 

Line 345: The reference Robinson and Stone, 2004) needs to be in the square brackets format to be consistent with the rest of the paper as does the reference to McNeil, 2019 in line 347. 

Lines 357-359: It is not clear why ‘1-2 hours’ and ‘2-3 hours’ and ‘3-4 hours’ and ‘more than four hours’ are on the same lines. Would it not make more sense for each category to have its own line? Especially as the difference between 1-2 hours and 2-3 hours is part of the study's cut off criteria. 

Figure 10: two of the eight images in this figure do not have subtitles, please add these in.

Lines 526-528: please revise the sentences to clarify as there is some confusing repletion: ‘it recorded the highest sunlight access rate at 98.05% with a FAR of 299.46%’ ‘Alternative four (Alt 4) applies pattern.02 ver.03, consisting of 15 buildings that achieve the highest sunlight access rate at 99.03%,’

Figure 16: Consider changing the colour of public green space in the figure to increase contrast with road space as this is currently hard to differentiate.

I hope that these comments help to make the article even better. 

 

Author Response

Main Comment 1: Provide visual examples of Visual Openness Ratio

Response: We have added a detailed explanation in Section 2.5.2 contextualizing VOR values:

• 100% VOR represents unobstructed 180-degree view
• Above 60% is considered satisfactory
• 40-60% is acceptable
• Below 40% needs improvement
• The existing complex's 39.48% average falls in the "poor" category

Visual diagrams showing different VOR levels (20%, 40%, 60%, 80%) are being finalized and will be included in the final submission.

Main Comment 2: Clarify structural implications of core modulation

Response: We have added a detailed explanation in Section 3.3.1 addressing:

• Need for structural engineering validation
• Potential 15-20% increase in construction costs
• Technical feasibility demonstrated by contemporary towers like Lotte World Tower
• Requirements for additional shear walls and moment frames

Main Comment 3: Discuss framework applicability to other scenarios

Response: This has been comprehensively addressed in the new Section 5.2 on generalizability and broader applications.

Main Comment 4: Add discussion of practical limitations

Response: We have expanded Chapter 6 to include:

• Construction cost implications (15-20% increase for core modulation)
• Regulatory challenges with current building codes
• Stakeholder negotiation complexities
• Construction phasing and temporary relocation considerations
• Market condition impacts

Minor Comments:

• FAR definition: Added in Section 1.1 (marked in red)
• Article citations: Added proper citations for Building Act Article 53 and Article 86
• Table 7 clarification: Added explanation of vertical vision grades
• Reference format: Unified all citations to [number] format
• Paper structure: Added outline at end of Section 1.2
• Figure improvements: Color contrast improvements are in progress
  
  

• Additional Improvements Made

  Beyond the specific reviewer comments, we have also:

  • Added comparative analysis with previous studies (Table 18)
  • Improved the logical flow between sections
  • Enhanced technical clarity throughout
  • Ensured consistency in terminology
  • Updated all references to maintain proper numbering sequence

  We believe these comprehensive revisions have significantly strengthened the manuscript and addressed all reviewer concerns. We are grateful for the reviewers' insightful comments that have helped improve the quality and clarity of our research.

  Thank you for considering our revised manuscript.