The authors present an interesting and relevant study on the interrelation of urban structure types and heat stress in the city of Berlin, more precisely, the difference between objectively measurable heat stress and the individually perceived heat stress. They base their analysis on spatial data processing, and statistics on population and to the different neighborhoods and districts from authorities and questionnaires. The results are novel and the quality is high, but partially explained not well enough for readers without previous knowledge on the city or the topic. Most of my comments address clarification of points which raised questions during the reading. I encourage the authors to invest time in making this an excellent paper. 

Abstract

• I recommend removing the urbisphere project from the abstract as it is not relevant in this context
• The abstract does not equally adresss problem statement, methods, results, and outlook, and largely focuses on the overall idea. Furthermore, it does not give much numeric results of which many were generated in the study. I recommend using the detailled summary from lines 352-360 in the abstract to present concise results for readers already and select some of the most relevant numbers.
• The aims of the study remain unclear in the abstract: is it to quantify perception, is it the difference between vulnerability and exposure? It becomes clearer in the study itself, but I would welcome a clear statement what is your highest aim with the presented study.

1. Introduction

• As you mention the increase of global air temperatures, you might add the proportionally larger increase within cities from selected references to put your study into this context
• The first part largely is based on IPCC references which are already a collection of research. It is suitable to mention the importance of the topic, but you could guide the reader to the original studies a several points to acknowledge their contribution
• I'm not clear about what you mean by "heat adaptation plans with marginalized people" and how this could look like. As you refer to this in the conclusion, it should be clearer how this could be achieved and by whom.
• It looks strange that the source is reduced to (Nature, 2021). I see that it is an editorial article but I personally think it should either include an author of the editorial team or refer to a study in this issue (595).
• The structure of the introduction seems a bit odd, the first paragraphs follow after 1. and give background information but at this length (1 page) it could also benefit from its own sub-heading (1.1). Also, the other sub-chapters (1.1 and 1.2) have indifferent roles in the article, but both address the state of reserarch. Would it make sense to separate the literature part from the problem statement, definition of the research gap and the aims of the study?
• You carefully list questions but do not mention the methods on how you plan to answer them. It is clear that they follow later, but you could as well give a one-sentence outlook on what is to expect.
• Again, highlighting the name of your research project in the last paragraph is rather uncommon and does not add relevant information. I'd say this belongs to the acknowledgments.

2. Methods

• The quotes of authorities in the text are partially very long (Deutscher Wetterdienst and Senatsverwaltung für Stadtentwicklung, 2010). Can you identify authords of the works and quote them accordingly? As an alternative, you could use abbreviations to make the citations in the text more compact.
• Again, you mention the urbisphere campaign, please stick to the references to existing papers.
• It is not logic to me that you present the city as a polycentric phenomenon but use (concentric) rings to describe it. This sounds contradictive to someone who is not involved in urban studies. Please clarify.
• Can you briefly mention how the reduction of 13 USTs to 7 classes was performed (e.g., "based on xy") or refer to a source where it is described? The table in Appendix A1 is not clear to me.
• The source to Senatsverwaltung (2021) does not explain how the USTs were delineated (data source, criteria, methods…) for Berlin, is there any information available?
• What do the labeled names in the map of Figure 1a represent? Maybe you can add this in the caption. Are these the Buroughs? Someone who is not from Berlin might get confused about what is a PLR and what is a Burough.
• You mention 39 residential addressses in line 152 but 38 in chapter 3.1 which is confusing
• Can you briefly explain the stratification process mentioned in line 153 that led to the sampling visible in Figure 2? If this is the case, please add a reference to Figure 2.
• If the survey was accessible by QR codes I suspect a bias towards the participation of elderly which are a focus group of your analysis. (How) can you be sure that the less technically affine population is included? I refer to this at a later point again with a constructive suggestion.
• I would welcome a flowchart which explains how different data sources, methods and information flow togehter in your analysis
• Table 2: Colum Q# indicates that the actual questionnaire was significantly larger. Please shortly explain the total size and topics and why you chose the 7 in your study.
• Lines 170-176: As you are describing how the results of your analysis will look like, please refer to each of the following sub-chapters where the correlations and plots are to be expected.
• Table 3: The table mentions 16 UST but in your paper 13 are mentioned as well, this is confusing
• Table 3: Parts of the captions “Analysis includes […] in Iqbal et al, 2024” this could be put I the text to make the caption more compact
• Table 3: I am not clear about the term indigenous residents (TDI)
• Table 3: “Copernicus Sentinel-2” seems redundant as a source if the quoted reference contains the actual data source and method, I’d prefer an either citation-based source or the consistent use of the underlying geospatial dataset (probably more complicated to add for all parameters).
• Figure 2: The boroughs, PLRs and blocks are not clear, why not showing the USTs for the entire city as this is your main unit of analysis?

3. Results

• As mentioned earlier, the 38/39 mismatch of PLRs must be resolved
• How were PLRs which range between several kilometers assigned to one interval?
• Figure 3: The order of a-d seems odd to me because b is at the bottom
• Figure 3c/d, Figure 4, Figure 5a: I don’t think violin plots are a legitimate choice here because the y-axis is of ordinal scale and the violin plots suggest a continuous variable. Stacked columns as in Figure 5c.
• Figure 3b and 3d: I suggest to name it “thermal discomfort index (TDI)” to make it clearer that this is the measure retrieved from other data then the perceived heat from the questionnaire.
• Line 234: “Statistically, more >65 year olds live in semi-detached and terraced houses” → please rephrase because it indicates an absolute dominance while it is just a proportional statement. For example, “a higher share of >65 year olds lives in semi-detached and terraced houses”
• Chapter 3.3.1: As you are correctly addressing statistical significance, it would be good to briefly mention the sample size of these calculations again in the beginning. If these calculations are only based on the 565 responses, I would suspect that the age bias of the survey methods (as indicated above) distorts the actual conditions. Would it help to display a histogram of the age groups of the questionnaire and a histogram of total Berlin’s population to proof that each group is equally represented? You could place this in the appendix to give your results more validity.
• Figure 4 b: Elderly people is missing a unit: “Share of elderly people (>65 years) [%]”
• Chapter 3.3.3.: I suspect that vegetation played already a role in in the delineation of the 13 USTs. If this is the case, Figure 7 just replicates the process of their generation and have no additional analytical value.

4. Discussion

• Lines 315-325 and 320-321: How should processes of urban planning and development address this call for action? Why does it matter if elderly live in B1 or B2? I agree that vulnerable people must be protected, but your plea for action is not very concrete here. Also in line 334-335: Which options do city planners have to include the aging process in cities? Doesn’t this mean that, in the end, all parts of the city are subject to demographic shifts and urbanization processes and have to be equally prepared for heat? In other words, how can knowledge about spatial patterns of thermal discomfort and heat stress actually help planning? As this is already the part of the outlook where you have to sell your study at the highest price (it does contain many new insights), who will be later using this information?
• Line 349: Consider removing “Role of the”

5. Conclusion

• As stated above, the first paragraph would make a good abstract already.
• Line 363: “Combined this” does not sound like a grammatically correct phrase.
• Line 367-368: I wonder how such a prioritization could look like. I think in the end all parts of the city have to be heat resilient and any attempt for local adaptation at the architectural level will be obsolete within years, as the city and its work force, elderly, etc. constantly change. But maybe I am just missing the point.
• Acknowledgments
• There is a fullstop in the list of authors where there should be a comma (“JB. SG”).

This paper examines how the perception of heat stress in Berlin differs depending on urban forms and human vulnerability profiles. The motivation behind this work - to understand drivers and perceptions of heat stress in order to inform adaptation plans - is important, and the work being done by these authors has the potential to contribute to improving heat adaptation planning.

Unfortunately, the use of rings to define perfectly circular zones radiating from the city center for analysis is arbitrary and likely masks geographic correlations that may be stronger than those found. The paper states that there are two city centers, yet the zones radiate from a single city center. Additionally, while cities tend to grow out from centers, they generally do not do so symmetrically due to geographic and historical influences. Defining zones within the city based on time of development, building types, population density, building density, development function (e.g. industrial, residential), and/or demographics would provide more logical geographic divisions to study.

A second methodological problem is the manner in which respondents were recruited for the study. Age of respondents is an important factor, but the use of a QR-code and an online survey would likely lead to a lower response rate from older people who are generally less accustomed to technology.

The final issue with the paper is the writing. Grammar and sentence structure are problematic in many places. The organization and development of ideas is also weak in some places. For example the second and third sentences of the introduction talk about the problem of heat in urban areas, but it is not until the second paragraph that the paper establishes that heat in urban areas is a separate problem from heat in general. A thorough edit for clarity is needed.

All that said, I think the data and the analyses are on the right track. With a better geographic analysis, this paper would have great potential for publication.