A Proposal for Measuring In-Use Buildings’ Impact through the Ecological Footprint Approach
Round 1
Reviewer 1 Report
The authors approach critical issues, such as the ecological footprint, for the urban sustainability, and state that not only the construction phase could add damages to the environment, but also the usage phase. They also discuss the variety of green standards and methodological issue in establishing buildings’ eco-efficiency.
The proposed new sustainability assessment tool is original, starting from previous ecological footprint studies. The model includes a variety of variables and seems to take everything into account. However, there is something I am not quite sure about, because there different opinions. That is the number of occupants of a building. According to the proposed model and the explanations of it (lines 271-280) the increasing number of the occupants decreases the building’s ecological footprint (which seems right) and consequently supports the sustainability. Regarding the last part, I am not sure about, as there are studies reflecting on the urban agglomerations and their environmental impact in terms of carbon emissions and generated waste. As I see it more people generates more carbon emission and more waste, even if they are living overcrowded in a building. If this is the case is there valid to subtract the number of occupants (O)? Some clarifying remarks on this matter are welcome.
The conclusions of the paper add value to it by further explaining the approach and its novelty but also identifying the limitations and possible developments.
Author Response
Dear Reviewer,
thank you for your comment, which makes us think a lot about some important aspects of our research.
To answer your question:
The presented model considers all the consumptions and waste generated by the building's users (Energy EF, Waste Generation EF, Food and Drink EF, etc.). In these estimations, the IEFA looks at the amount of land consumed to cover the demand. And, one of the six lands is the CO2 sinks, which calculates the carbon emissions. While Occupant EF shows how the simultaneous use of some resources is shared among users. Think about the light on in a room. If more people are present at the same time, electricity consumption must be divided between them and, therefore, globally it will have a lower weight.
Reviewer 2 Report
Thank you for the opportunity to review this interesting look at EF and its application to the built environment. I believe that the paper points to an interesting idea that is worth of additional research. I cannot comment on whether the paper advances substantially beyond prior case study applications of EF, but the case study here appears to be appropriate and useful. I am also unable to provide much comment on the validity of the methodology and assumptions. With those caveats, here are more specific reactions and suggestions: Line 44-45: “Among technical problems, each rating system is the result of building standards that vary from 45 country to country.” I’d note that there is also a problem of inconsistent sub-national standards – perhaps even more difficult from an implementation standpoint than varying national standards. 81: “The EF concept is supported as a solution-oriented approach by the science of sustainability [27]” It is not clear that the cited reference supports this assertion. While the cited paper by Sala et al. indeed discusses the characteristics of a solution-oriented approach in sustainability science, it’s less clear (absent further explanation or analysis) that EF is consistent with Sala et al.’s framework. I think I see the tie-in to biocapacity as outlined in the subsequent paragraph, but not yet convinced (because the biocapacity discussion seems to support more the idea that EF is a reasonable measure for evaluating the built environment’s contribution to sustainable development, rather than supporting the assertion that it is a “solutions-oriented” approach as described by Sala et al.). 300-301 (and related section): I am unable to provide much constructive comment on the methodologies outlined in this section of the paper. However, two questions jump out at me. 1. With respect to electricity consumption, does the use of Italy’s national emission factor hide important differences in the way the built environment’s electricity consumption can vary with time? For example, on a solar-rich grid, the EF of a building whose demand peak is in the middle of the day would be substantially different than one whose demand is relatively flat (or peaks at nighttime). This appears to be an issue of growing importance, and for EF to work as a building metric it probably needs to account for more granular energy consumption characteristics? Note that this also seems relevant to the conclusion that building users contribute substantially to EF – building users could, through either conscious, unconscious, or automated demand shifting/management, alter a building’s emission factor. Since the conclusion focuses on this role of users, the idea that it is omitted from the energy metric seems inconsistent and problematic. 2. Overall, does utilizing the EF methodology create room for significant uncertainties or errors, created by utilization of a variety of assumptions in the underlying calculations. I am reminded of the work by Garvin Heath et al. on harmonizing life cycle emissions assessments. Can EF work without similar harmonization of assumptions? (noted on line 448 of the conclusion). Perhaps harmonization approach should be recommended as a future line of inquiry in lines 446-461? Table 8. With respect to supporting the conclusions about EF’s applicability to building standards, it would seem most useful to find instances where EF has been applied simultaneously with another standard – and then to evaluate differences to understand where EF over- or under-performs. 464-466: “A crucial question yet to be answered is: do gha, number of 465 Earths or football fields induce people to implement sustainable policies and adopt sustainable 466 behaviors more effectively than other carbon metrics or energy consumption measures?” There is substantial work on these issues of how sustainability metrics impact, or not, human behavior. I’d be surprised to learn that this hasn’t been considered with respect to how users interact with the built environment. At the very least, I’d expect there to be theoretical frameworks for evaluating how we might expect the EF metric to over- or under-perform other metrics. E.g. the work of Daniel Kahneman et al. One might also review whether presenters at the various Behavior, Energy, and Climate Change conferences have written on this issue. https://peec.stanford.edu/events/becc Minor awkward uses of English language in: 23-24: “This highlights the need for integrating a sustainable culture in building’s users.” In “a building’s users”? Or “in building users”? 76-77: “Green certifications miss to express the concept of inefficiency.” I believe the word “fail” is intended rather than “miss.”
Author Response
Dear Reviewer,
thank you for you comment, which makes us think a lot about some important aspects of our research.
We have reviewed some parts and deepened the sources you mentioned.
To answer your questions:
1) Yes, we believe it is very important to consider the peak of use. EF can show the excessive and/or bad use of the built environment. While, building managers are responsable for taking actions to improve the use of buildings.
2) The research of Garvin Heath et al. is very interesting. We have read it and we think it will be useful for future implementation of our model. IEFA is built on many assumptions and it depends on the inventory done for the analysed building. Therefore, applying the model to multiple case studies will improve the model and harmonize the calcultions and the data collecting.
Reviewer 3 Report
This research topic is very important and crucial in today's world, where we have overpopulation and global warming. Many people are not aware of the consequences that are coming as the byproduct of global warming, thus it is on the scientists and publications like this to educate the public on the current and future issues related to global warming of the Earth. The paper is very well written, with plenty of support material, on topic that is necessary in today's world. Minor grammars mistakes are present, where sentences could be rephrased, but in general great job on the paper.
Author Response
Dear reviewer,
thank you for your positive comment.
We spent some time reviewing the text and correcting some mistakes.
