Space Efficiency in Contemporary Supertall Residential Buildings
Round 1
Reviewer 1 Report
It is an interesting article, about an increasingly relevant issue in the field of height architecture, and the efficiency of space in this type of construction.
However, although this study specifically analyzes the efficiency of space in supertall residential buildings from 2000 onwards, it would be convenient to establish a minimum and brief “state of the art” about the historical trajectory of this type of buildings.
On the other hand, the Introduction could also raise, although it was only in a generic way, the environmental consequences of continuing to build this type of construction. Something should also be said about the circular economy, and how unsustainable these supertalls are.
In this sense, citations to publications such as:
- Milagrosa Borrallo-Jiménez, María LopezdeAsiain, Rafael Herrera-Limones and María Lumbreras Arcos. Towards a Circular Economy for the City of Seville: The Method for Developing a Guide for a More Sustainable Architecture and Urbanism (GAUS). Sustainability 2020, 12.
… And some more specifically referred to specific sustainability issues.
Regarding the Conclusions, these topics suggested in the Introduction should also appear. Regarding the figures, it is considered that their level could be improved in the article, providing some of greater interest, allowing a contextual fit of the buildings analyzed in their immediate urban environment.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this paper the author investigates the space efficiency of 16 super-tall buildings employed for residential purposes. Specifically, the author separates the buildings depending on the core type, building form, structural system and material. Then, it analyzes the space efficiency and core to gross floor area ratio, with emphasis on the influence of the building height.
The manuscript is interesting, fits well with the aim of the “Architecture” Journal, but in my opinion it can be accepted for publication only after major revisions.
(1) Very importantly, at lines 228-229, the author writes: “As the building gets higher, space efficiency decreases as indicated by the red trendline in Figure 5”. However, the red trendline reported in Figure 5 shows that the average space efficiency gets somewhat higher for taller buildings. Similarly, at lines 236-238, it is written: “Additionally, Figure 6 illustrates the ratio of core over gross floor area as another indicator of the fact above, the taller the building, the more service core space needed as shown by the red trendline in the figure below”. In this case, the red line shows a slight decrease for increasing building height. So, I don’t quite understand how the author is drawing the conclusions based on these graphs. These do not seem to support the fact (stated by the author) that taller buildings lead to lower space efficiencies as well as higher core over gross floor area ratios.
(2) In relation to Figures 5 and 6, the statistical details related to the red trendlines should be reported, e.g. equation of the fitted line (y = ax + b) and the R2 fitting parameter. Also, from the graphs, it seems that two points can be considered as outliers (buildings with heights of 330/340 m, with a space efficiency of 55% and a core ratio of 35%). A discussion about these points should at least be provided. Also, how does the trendline get affected if those points are removed from the fitting procedure?
(3) Two oversights should be corrected in Table 1. For the 432 Park Avenue building, the “United States” label is not completely visible. For the Torch, “86” should be “86 stories” to keep consistency with the other buildings.
(4) Finally, the author considers different features for the 16 buildings, such as their core type, building form, structural system and material. However, these properties are only reported in Table 2 and not used for any analysis. I was expecting (while reading the paper) that the author would correlate the space efficiency to some of these features. Except for the case of the core type and material, where there is a strong prevalence of a single type (central core and RC), there is in fact some variability in the other two features, i.e. building form (prismatic, free, tapered and twisted) and structural system (framed tube, outriggered tube, diagrid-framed-tube). In my opinion, the authors should try and correlate the obtained space efficiency values with these features in order to answer these important questions: how do the building form and adopted structural system influence the space efficiency? If not possible to find a statistically relevant correlation (maybe because of the lack of a high number of investigated buildings), the author should at least mention how the space efficiency might depend on these features, which play a huge role in every tall building design.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
After the review, the author has taken into account the points raised by this reviewer. However, in my opinion, the major concerns emerged during the review process have not been tackled successfully.
In particular:
- The major concern which still remains in the current version of the manuscript is that it is not still clear whether taller buildings lead to higher or lower space efficiency values (which is supposed to be the main result of this analysis). From Figures 1 and 2, it seems that taller buildings lead to slightly higher space efficiencies and lower core areas. However, the correlation of the regression lines with the data is very poor (R2 around 1%), so from the data one couldn’t really say whether from the selected dataset taller buildings lead to higher or lower space efficiency values. It follows that there is no conclusion for the selected dataset of supertall buildings.
- Moreover, the presence of the outliers in those figures has not been explained thoroughly. I would have expected two graphs, one with the outliers and another without the outliers in order to see how these affect quantitatively the regression lines (maybe those graphs might be provided in the author’s responses, if the author does not want to put both in the manuscript).
- Finally, although the author provides some general comments about the possible relationship between the building features (structural system, floor shape, etc.) on space efficiency (lines 247-253), no detailed connections between these features and the space efficiency has been provided. Why showing these data if no detailed correlation can be provided with the space efficiency (which is the focus of the paper)?
According to what said above, the reviewer’s opinion is that the manuscript cannot be accepted for publication in its present form. I might recommend the author to revise it (one suggestion is to enlarge the dataset of supertall buildings, or including tall buildings below 300 meters as well) and submit it again when the conclusions are quantitatively supported by the results.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 3
Reviewer 2 Report
After reading the new version of the paper, I can confirm that the author has now successfully addressed all my previous points. As a matter of fact, the dataset of super tall buildings has been enlarged, separate graphs related to the presence or absence of the outliers have been included in the manuscript and a specific description of the influence of the building form or structural system on the space efficiency has been included. For this reason, my opinion is that the paper can now accepted for publication.
Just as a final suggestion, regarding Figures 2 and 3, I would like to suggest the author to put the equation of a regression line and not that of an exponential. So, the line can be described by an equation like “y=ax+b”.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
