Natural Ventilation Strategies to Prevent Airborne Disease Transmission in Public Buildings

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This is interesting work but very poorly written and referenced. The attached file has many comments. 

Comments for author File: Comments.pdf

Author Response

Reviewer 1

The authors are grateful to reviewers for the valuable comments and time expended to do the revision. We attempted to respond to the reviewer’s comments correctly and clearly in this response letter. Items corrected are already incorporated in the paper and highlighted in yellow.

Comments on grammar and spelling for Authors” (the changes have been marked in bold and new paragraphs have been highlighted in yellow):

The following aspects indicated by the reviewer have been modified in the paper:

• In the Abstract section:

…based on carbon dioxide…

…suggested to reduce disease spread.

• In the Introduction section:

…it is necessary to regulate indoor pollutants presence [11, 12].

…design represents a promising method of removing indoor pollutants [14-16], as well as…

…of windows is a suitable methodology for…

…are small, in addition to depending on dimensionless discharge coefficient that considers turbulence and air viscosity that are somewhat ambiguous in nature [33]. 

The word ‘uncomplicated’ is removed, as its presence is due to a review error.

Furthermore, numerical approaches are based on concentration of environmental pollutants, whereas the role of buildings configuration and occupants’ behaviour is only considered in specific studies [2], such as…

Carbon dioxide (CO₂) is commonly used as a chemical compound…

It has been shown as bioeffluent indicator to be effective in reducing the risk of aerosol-borne respiratory diseases such as the SARS-CoV-2 infection…

…flow rate that is necessary per occupant. There are different ventilation rate standards with a combination of 2.5 l/s per person plus 0.3 l/s per m² of floor space being accepted [41], 12.5 l/s for office premises [42], and 13.9 l/s in work environments, which can be reduced to 8.3 l/s for sedentary work in unpolluted environments [43]. It should be noted, however…

…it has been considered that 14 litres per second per person…

The following sentence has been removed from the document: This is contingent upon the specific conditions of the room in question.  

As previously stated, many standards for indoor air quality are determined by assessing the carbon dioxide concentration…

…flow rates exceeding five air changes per hour have been…

…is a maximum of three air changes per hour [11].

…in order to guarantee optimal ventilation, carbon dioxide…

…based on these indicators [2], including…

…based on the monitoring of carbon dioxide (CO₂) gauges is devised…

• In the Background section:

…upon the evaluation of external wind pressure between the windward and leeward sides of the structure.

The following is deleted from the text: of the disparity in

In all the cases analysed, the possibility of natural ventilation is limited to the available casement windows. Due to the vertical distance between the upper and lower openings is minimal in comparison to their horizontal distance. In such circumstances, the effect of buoyancy-induced ventilation is diminished and no longer a significant factor.

The authors agree with the reviewer that it is appropriate to change the location of the indicated paragraph, removing it from the background section and moving it to the materials and methods section.

The authors thank the reviewer for their comment regarding ‘You probably don't need so many significant figures in these dimensions.’ However, to facilitate reading of the text, an image of the main municipal building, the town hall, is provided to allow the reader to understand the scale of the buildings under study and to see an image of the building that houses the facility used as an example of application: the plenary hall.

Thanks to the reviewer's comments, temperature and wind speed units have been included in Table 1. The abbreviation for the month of August has also been modified.

• In the Materials and Methods section:

The theoretical occupation is determined…  

…reference value based on Category IDA2 [47], 172 with…

In the event of infectious disease, four supplementary safety 174 levels…

The generation rate depends on sex, body mass and age [52], however, an average person, considered as such a 70 kg weight and 1,7 m height man [53], engaged in light activity generates…

Therefore, the ventilation flow rate required per person to achieve IDA2 air quality implies that the concentration of carbon dioxide (CO₂) between the interior and exterior must be less than 500 ppm.

The authors thank the reviewer for detecting the error in the equation (), which has been modified according to their instructions. To this end, the following legend has been added:

Where:

Q_{required RITE} = Volumetric flow rate of air required for achieving RITE's quality level IDA2 (m³/s)

q_co2 = CO₂ emissions generated by one person during a light activity (l/s)

The authors agree with the reviewer on the need to include an explanation of the origin of the reference values used. As a result, the following paragraph has been added:

Value similar to the 45 m³/h per person required by regulations to consider air quality IDA2 (RITE).

Considering this value as a reference threshold, the classic action levels are established, as a methodology in Industrial Hygiene, at 75%, 50% and 25% of this limit, i.e. 15.62 l/s, 18.75 l/s and 21.87 l/s. Consequently, the reference values for ΔCO2 are, respectively, 230 ppm, 270 ppm and 320 ppm. Assuming an outdoor concentration of between 400 ppm and 500 ppm, the reference values indoors will be 730 ppm, 770 ppm and 820 ppm.

The safe concentrations of carbon dioxide (CO₂) for infectious disease are 730 ppm…

…of the theoretical occupancy of the enclosure at the various levels of air quality, as indicated by…

The outdoor air velocity is closely related to the available ventilation. By comparing the observed value of outdoor air velocity with the reference value (Q_required), the occupancy can be determined. The outdoor air velocity is an extremely fluctuating value that requires the adoption of the most unfavourable conditions of the values provided in the scientific literature [40].

Following the reviewer's instructions, the sentence is rewritten to make it easier to understand.

In order to circumvent the utilisation of statistical values, standardised air velocities are employed, which are routinely employed in the determination of dangerous areas due to fire and explosion risk and entail a high level of security. The air velocity

The following sentence is deleted: In the city of Mostoles, the lowest mean wind speed at a height of two metres during the year 2023 was between 0.84 and 1.33 metres per second. In order to circumvent the  

The authors would like to share with the reviewer the fact that the wind speed shown was based on the analysis of the AEMET climate values. However, standardised values are used in the article, and we therefore consider that it is not appropriate to include a table with climate values that were not subsequently used in the study, as this would make it difficult for the reader to follow the thread of the text.

Due to its density, 1.5 times heavier than air, carbon dioxide is prone to accumulating in low-lying areas, where ventilation is typically reduced.

The authors would like to share with the reviewer that we do not consider CO₂ to accumulate in low-lying areas, but rather that standard UNE 60079-10-1 establishes different effective dilution rates depending on the relative density of the gas under study: whether it is denser or less dense than air.

Table 4 indicates the effective velocities that should be considered for a gas denser than air emitted from different heights above ground level.

The ventilation of an enclosure can be expressed as the vector sum of the airflow induced by wind speed and buoyancy [60-62].

A variety of empirical and theoretical procedures is available for establishing the natural ventilation of an enclosure. These include the British Standard [62], as well as the Building Research Establishment [64], and AIDA [65, 66].

The authors agree with the reviewer on the need to remove the ASHRAE method [60] and Lawrence Berkeley Laboratory methodologies from the text.

The dilution is determined based on the speed of the air passing through the section perpendicular to the location of the windows in the enclosure under study. It is obtained by the following equation:

The word ‘airflow’ has been modified throughout the document.

Q_w = Outdoor airflow through the considered space

The volume of polluted indoor air is calculated by dividing the calculated value of the outdoor airflow rate (Q_w) by the actual ventilation flow rate in the space under consideration (V_o), in the vicinity of the emitting person [59].

The calculations are based on the wind induced by the pressure difference between the windward and leeward sides of the building, in the absence of an air conditioning system.

The Plenary Hall is situated within a naturally wind-ventilated edifice. It is situated

Furthermore, the effect of buoyancy-induced ventilation is negligible, due to the vertical distance between the upper and lower apertures [71,72].

Where:  

Q_a = Volumetric airflow rate (m³/s)

C_d = Dimensionless discharge coefficient, characteristic of large ventilation openings and considering turbulence and viscosity, typically between 0.5 and 0.7

C_w = Coefficient due to wind direction 0,07 -0,14

A_r = Upper ventilation area (m²)

ΔT = Difference between outdoor and indoor temperature (K)

T_out = Outdoor temperature (K)

g = Acceleration due to gravity (9,81 m/s²)

H = Vertical distance between the lower and upper opening points (m)

u_w = Wind speed at referenced height (m/s)

• In the Results section:

The data pertaining to the characteristics of the buildings, the Town Hall, the Citizen Participation Centre or Junta I, the Junta 4 West building, Rodolfo Halffter Conservatory, the Kaleidoscope Sociocultural Centre, the El Soto Sociocultural Centre, the Villa de Mostoles Sociocultural Centre, the Ramón Rubial Social Centre, the Ribera Youth Space, the General Services and the Almudena Grandes Central Library, as well as the capacity and the maximum opening area of the windows, were provided by the Mostoles City Council.

Following the reviewer's instructions, the unit of measurement for Tables 10 to 18 regarding occupancy is added, which is defined as follows: (dimensionaless).

To this end, clarification has been provided by adding an example showing that these are dimensionless units, as they are the result of applying:

The Plenary Hall is located on the third floor of the Town Hall building. The occupancy that allows IDA2 air quality with all windows open on both sashes is 20 people (Table 8). The room is designed for 77 people. The IDA2 occupancy relative to the design occupancy is:

 

• In the Discussion section:

The scientific literature has highlighted the importance of natural ventilation as a potentially useful strategy for reducing airborne disease transmission in the case of COVID-19. The first accepted model suggests the need for five air changes per hour in enclosures to control transmission [44, 45], while more…

On the other hand, natural ventilation has been shown to be a key ally in reducing the transmission of diseases caused by both viruses and the concentrations of harmful chemical compounds in indoor environments.

• In the Conclusions section:

This study demonstrates the effectiveness of natural ventilation as a fundamental mechanism for improving air quality in public buildings, showing that cross ventilation is the only way to achieve recommended air quality standards [44, 47], especially in high occupancy environments. This is critical in high-capacity spaces, where the risk of transmission of respiratory diseases is high and five air changes per hour are required to maintain IDA2 air quality [44, 45].

 

 

 

 

Reviewer 2 Report

Comments and Suggestions for Authors

1. Engineering Drawings: Please include a schematic engineering drawing of the buildings studied to clearly illustrate the details of the ventilation systems.
2. Table 1 Correction: In Table 1, please change the abbreviation "Ago." to "Aug." for clarity.
3. Unit Consistency: On line 262, please change "Kg" to "kg" to adhere to standard scientific notation.
4. Flowchart for Clarity: To enhance the clarity of your analysis, please add a flowchart summarizing the calculation steps.
5. Discussion of Results: The results section contains several tables that lack accompanying discussion. Please ensure all tables are thoroughly discussed and interpreted within the text.
6. Table Presentation: In the results section, consider merging some tables where appropriate and presenting them in landscape orientation to improve readability, especially for larger datasets.
7. Figure 5 Labeling: For Figure 5, please add the parameter name and its unit to the y-axis for proper interpretation.
8. Software Details & Simulation Setup: It is currently unclear which software was used for this analysis. Please provide full details about the simulation setup, including the software name, version, and any relevant parameters.
9. Results Validation: Please explain how the results of this analysis can be validated. What methods or comparisons were used, or could be used, to confirm the accuracy of your findings?

 

 

Author Response

Reviewer 2

The authors are grateful to reviewers for the valuable comments and time expended to do the revision. We attempted to respond to the reviewer’s comments correctly and clearly in this response letter. Items corrected are already incorporated in the paper and highlighted with yellow underline.

Comments 1: Engineering Drawings: Please include a schematic engineering drawing of the buildings studied to clearly illustrate the details of the ventilation systems.

Response 1: The authors agree with the reviewer that the inclusion of a floor plan of the building is useful for illustrating the details of the available ventilation systems to the reader. However, due to the number of buildings analysed in the document, many of which have several floors, this is difficult to achieve. In any case, following the instructions, a floor plan of the General Services building has been included to convey to the reader the fundamental idea of the work: the incorporation of natural cross ventilation in building design is feasible, so we present a calculation methodology that allows for its implementation, ensuring a previously established air quality based on the building's design occupancy.

For this reason, the following paragraph and a floor plan of the General Services building have been included in the paper.

The General Services building is a single-storey building with casement windows, but these only allow cross ventilation in the administration area (Figure 3).

 

Figure 3. Ground floor plan of the General Services building.

Comments 2: Table 1 Correction: In Table 1, please change the abbreviation "Ago." to "Aug." for clarity .

Response 2: The authors thank the reviewer for detecting the error and have modified the text: ‘Aug.’ Thanks to the reviewer's comments, temperature and wind speed units have been also included in Table 1.

Comments 3: Unit Consistency: On line 262, please change "Kg" to "kg" to adhere to standard scientific notation.

Response 3: The authors thank the reviewer for detecting the error and have modified the text: ‘(kg/m³)’. The authors are grateful for the reviewer's point of view and incorporate figure 11 into the document and its explanation in the interest of improving firefighting practice.

Comments 4: Flowchart for Clarity: To enhance the clarity of your analysis, please add a flowchart summarizing the calculation steps.

Response 4: The authors agree with the reviewer that the inclusion of a flow chart to facilitate understanding of the proposed calculation method is entirely appropriate and relevant. Therefore, the following diagram has been added to the paper, along with some introductory text:

The calculation process consists of three phases. First, the required air quality is established. Second, the ventilation flow rate per person necessary to achieve the previously established air quality is determined. Finally, the occupancy that allows these conditions to be met based on the available natural ventilation is determined (Figure 4).

Figure 4. Flowchart process diagram.

As an example of an application that facilitates understanding of the results tables (Tables 10 to 18):

The Plenary Hall is located on the third floor of the Town Hall building. The occupancy that allows IDA2 air quality with all windows open on both sashes is 20 people (Table 8). The room is designed for 77 people. The IDA2 occupancy relative to the design occupancy is:

 

Comments 5: Discussion of Results: The results section contains several tables that lack accompanying discussion. Please ensure all tables are thoroughly discussed and interpreted within the text.

 Response 5: The authors agree with the reviewer that it would be beneficial to include a discussion of the results to enable the reader to interpret the tables presented. Therefore, the following text has been added to the paper:

Table 10 shows that 70% of the locations with the possibility of natural ventilation in the Citizen Participation Centre / Junta I building allow for IDA2 air quality to be achieved.

Table 11 shows that 22.2% of locations with natural ventilation potential in Town Hall building allow IDA2 air quality to be achieved.

Table 12 shows that none of the locations with natural ventilation potential in the Junta 4 West building allow IDA2 air quality to be achieved.

Table 13 shows that despite having cross ventilation in the adult room, study room and youth room, which are designed to accommodate a very large number of occupants, it is not possible to maintain adequate air quality by opening the windows alone.

Table 14 shows that it is not possible to maintain adequate air quality at the Rodolfo Halffter Conservatory with the available operable windows.

Table 15 shows that the Kaleidoscope Sociocultural Centre/El Soto/Villa de Mostoles centres only have cross ventilation in the library, and their high occupancy levels prevent adequate air quality from being achieved with natural ventilation alone.

Table 16 shows that the Ramón Rubial Social Centre is located on the ground floor of a residential building and, although it has casement windows, these are small and do not allow for cross ventilation.

Table 17 shows that the first floor of Ribera Youth Space is located on the ground floor of a residential building and has casement windows, but these do not allow for cross ventilation.

As demonstrated in Table 18, the General Services building is a single-storey structure with casement windows. However, these windows permit cross ventilation exclusively within the administration area.

Comments 6: Table Presentation: In the results section, consider merging some tables where appropriate and presenting them in landscape orientation to improve readability, especially for larger datasets.

Response 6: The authors agree with the reviewer that the presence of a large number of data and tables can cause the reader to lose track of the text, but on the other hand, we believe that showing the current conditions of a large number of buildings used for different activities allows the reader to have a clear idea of the capabilities that the incorporation of natural ventilation currently offers in terms of air quality in these buildings and the importance of having considered this possibility in their design.

First, the horizontal orientation of the tables in the document was tested, but it was found that this did not improve readability, as the data they contain is better suited to vertical orientation, given that there are no additional columns.

Comments 7: Figure 5 Labeling: For Figure 5, please add the parameter name and its unit to the y-axis for proper interpretation.

Response 7: The authors appreciate the reviewer's comment. However, given that this is a table that only shows percentages, it is considered sufficient to incorporate the units on the X-axis, including: Percentage (%)

Comments 8: Software Details & Simulation Setup: It is currently unclear which software was used for this analysis. Please provide full details about the simulation setup, including the software name, version, and any relevant parameters.

Response 8: The authors did not use specific software to perform simulations but only used Excel tables containing data provided by the Mostoles City Council to subsequently implement the equations shown in the paper. They agree with the reviewer that the incorporation of software such as Computational Fluid Dynamics (CFD) could improve the analysis of the facilities.

Comments 9: Results Validation: Please explain how the results of this analysis can be validated. What methods or comparisons were used, or could be used, to confirm the accuracy of your findings?

Response 9: The authors thank the reviewer for their comments.

Using CO₂ concentration as a parameter, automated detection systems can be integrated to validate the theoretical results. Furthermore, as these have been obtained from restrictive air velocities standardised in regulations for the calculation of explosive atmospheres, the actual occupancy of the building, which will generally be higher than the calculated occupancy, can be dynamically adjusted.

Also, to avoid using such restrictive values for available natural ventilation during the building design process, atmospheric simulation and prediction models can be implemented and adapted to any regulations governing indoor air quality through the required ventilation flow rate per person (Q_required).

 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Historically, the concept of mechanical ventilation in public buildings was not a factor in design considerations. These spaces did not necessitate higher standards of indoor air quality. The only potentially deleterious substances produced by human presence were heat caused by human metabolic processes and carbon dioxide (CO2). The impact of the outdoor environment was not as adverse as it is today (traffic noise, dust, and especially the negative impact of solar radiation during the warm season, with the greatest impact during the summer months).

However, there has been a notable shift in the outdoor climate, with natural ventilation being progressively superseded by forced ventilation. This shift is primarily attributed to the necessity of regulating air quality in real-time, with parameters including purity, temperature, relative humidity, air flow, and air flow velocity.

The primary disadvantage associated with forced ventilation is its spatial requirements. This principle is applicable not only to the designated ventilation machine room, a space allocated for the installation of one or more ventilation units, but also to the extensive pipe network utilised for air supply and exhaust, characterised by substantial pipe dimensions. The aforementioned factors frequently render the implementation of forced ventilation in older or listed historic buildings impractical.

Consequently, a re-examination of the layout of buildings is warranted, with a view to ascertaining whether sufficient ventilation of interior spaces through natural means is facilitated, thus ensuring compliance with the values stipulated by binding legal regulations. This is precisely why the topic of this article is highly relevant.

The article is clearly written, with individual chapters following on logically from one another. However, I consider it necessary to point out certain aspects that need to be corrected in order to improve the quality of the article for both the scientific community and professional practice:

- line 168 / Table 1 – the table lacks units of measurement; these must be specified for both temperature and outdoor air flow velocity. Why are the abbreviations for some months written in italics? Is the abbreviation for August correct?

- line 180 / formula – the formula number (3.1) is missing; explanations of the individual variables in the formula are missing (where: ...)

- line 260 / where: - the units of measurement for the individual physical quantities are missing

- line 349 / Table 8 – it is not clear from the table in which units of measurement the numbers are given

- for individual buildings, a floor plan of a typical floor would be very helpful for the reader's better understanding. It is important to point out whether cross ventilation can be ensured on a given floor

- overview of the literature dealing with this issue should not be part of the introduction; it should be given a separate chapter.

 

 

Author Response

Reviewer 3

The authors are grateful to reviewers for the valuable comments and time expended to do the revision. We attempted to respond to the reviewer’s comments correctly and clearly in this response letter. Items corrected are already incorporated in the paper and highlighted with yellow underline.

Comments “Comments and Suggestions for Authors”: Historically, the concept of mechanical ventilation in public buildings was not a factor in design considerations. These spaces did not necessitate higher standards of indoor air quality. The only potentially deleterious substances produced by human presence were heat caused by human metabolic processes and carbon dioxide (CO2). The impact of the outdoor environment was not as adverse as it is today (traffic noise, dust, and especially the negative impact of solar radiation during the warm season, with the greatest impact during the summer months).

However, there has been a notable shift in the outdoor climate, with natural ventilation being progressively superseded by forced ventilation. This shift is primarily attributed to the necessity of regulating air quality in real-time, with parameters including purity, temperature, relative humidity, air flow, and air flow velocity.

The primary disadvantage associated with forced ventilation is its spatial requirements. This principle is applicable not only to the designated ventilation machine room, a space allocated for the installation of one or more ventilation units, but also to the extensive pipe network utilised for air supply and exhaust, characterised by substantial pipe dimensions. The aforementioned factors frequently render the implementation of forced ventilation in older or listed historic buildings impractical.

Consequently, a re-examination of the layout of buildings is warranted, with a view to ascertaining whether sufficient ventilation of interior spaces through natural means is facilitated, thus ensuring compliance with the values stipulated by binding legal regulations. This is precisely why the topic of this article is highly relevant.

Response “Comments and Suggestions for Authors”: The authors thank the reviewer for their kind words and share their point of view, agreeing on the importance of incorporating natural cross ventilation in buildings to ensure the quality of the air breathed by occupants inside the building. Consequently, this idea has been incorporated into both the abstract and the conclusions, clearly establishing the novelty in this field of research:

• In the abstract section:

…and limit airborne disease transmission. Natural ventilation can be incorporated into building design as the primary mechanism for achieving the required indoor air quality, equipping buildings with operable windows based on their intended occupancy. Using eleven public…

• In the conclusions section:

…to maintain IDA2 air quality [44, 45].

To this end, a methodology is presented that allows the design of more sustainable buildings, incorporating the possibility of establishing natural ventilation as the main mechanism for obtaining the desired indoor air quality, by providing an openable surface in the building's windows, depending on the expected occupancy.

It was also observed that the model developed…

Comments 1: The article is clearly written, with individual chapters following on logically from one another. However, I consider it necessary to point out certain aspects that need to be corrected in order to improve the quality of the article for both the scientific community and professional practice: line 168 / Table 1 – the table lacks units of measurement; these must be specified for both temperature and outdoor air flow velocity. Why are the abbreviations for some months written in italics? Is the abbreviation for August correct?

Response 1: The authors thank the reviewer for detecting the error and have modified the text: ‘Aug.’ The italicised text in the table is replaced. Thanks to the reviewer's comments, temperature and wind speed units have been also included in Table 1: Temperature (°C), Wind speed (m/s).

Comments 2: Line 180 / formula – the formula number (3.1) is missing; explanations of the individual variables in the formula are missing (where: ...).

Response 2: The authors thank the reviewer for detecting the error and have incorporated the following text into the paper:

Where:

Q_{required RITE} = Volumetric flow rate of air required for achieving RITE's quality level IDA2 (m³/s)

q_co2 = CO₂ emissions generated by one person during a light activity (l/s)

Comments 3: Line 260 / where: - the units of measurement for the individual physical quantities are missing.

Response 3: The authors thank the reviewer for detecting the error and have incorporated the following text into the paper: 

Where:

P_w = Pressure due to wind (Pa)

C_p = Pressure Coefficient (Dimensionless)

 = Density of air at the desired temperature (kg/m³)

u_w = Wind speed at referenced height (m/s)

 Comments 4: Line 349 / Table 8 – it is not clear from the table in which units of measurement the numbers are given.

Response 4: The authors agree with the reviewer on the need to clarify the origin of the units used in Table 8, and this has been incorporated into the paper.

Table 8. Occupation of the Plenary Hall.

Conformation of openings	IDA2 (persons)	Safety level I (persons)	Safety level II (persons)	Safety level III (persons)	Safety level IV (persons)
All windows open both sashes	20	9	10	13	15
All windows open to a single sash	10	4	5	6	7
All windows open single sash except the casement (tilt and turn position)	16	7	8	10	12
One open window, both sashes, on each wall	11	5	6	7	8
One open window, one sash, on each wall	5	2	3	3	4

 

 

Comments 5: For individual buildings, a floor plan of a typical floor would be very helpful for the reader's better understanding. It is important to point out whether cross ventilation can be ensured on a given floor.

 Response 5: The authors agree with the reviewer that the inclusion of a floor plan of the building is useful for illustrating the details of the available ventilation systems to the reader. However, due to the number of buildings analysed in the document, many of which have several floors, this is difficult to achieve. In any case, following the instructions, a floor plan of the General Services building has been included to convey to the reader the fundamental idea of the work: the incorporation of natural cross ventilation in building design is feasible, so we present a calculation methodology that allows for its implementation, ensuring a previously established air quality based on the building's design occupancy.

For this reason, the following paragraph and a floor plan of the General Services building have been included in the paper.

The General Services building is a single-storey building with casement windows, but these only allow cross ventilation in the administration area (Figure 3).

 

Figure 3. Ground floor plan of the General Services building.

Comments 6: Overview of the literature dealing with this issue should not be part of the introduction; it should be given a separate chapter.

Response 6: We thank the reviewer for their comment. We agree that, in many cases, an extensive literature review can benefit from being developed in a separate chapter. However, in this specific case, we believe that its inclusion in the introduction helps to maintain the coherence of the argument and promotes a logical progression of the text, by immediately placing the reader in the conceptual and empirical framework that underpins the research problem. For this reason, we propose maintaining the current structure, unless the journal explicitly requires a formal separation of this section.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

Dear Authors,

too many data and tables, please re-organize article in order to explain cleary what is important and what it is'nt. A research aims paragraph and a workflow flowchart should be useful. Please explain your novelty of research field, article cannot be just a enginnering report.

Author Response

Reviewer 4

The authors are grateful to reviewers for the valuable comments and time expended to do the revision. We attempted to respond to the reviewer’s comments correctly and clearly in this response letter. Items corrected are already incorporated in the paper and highlighted with yellow underline.

Comments “Comments and Suggestions for Authors”: Dear Authors, too many data and tables, please re-organize article in order to explain cleary what is important and what it is'nt. A research aims paragraph and a workflow flowchart should be useful. Please explain your novelty of research field, article cannot be just a enginnering report.

Response “Comments and Suggestions for Authors”: The authors agree with the reviewer that the presence of a large number of data and tables can cause the reader to lose track of the text, but, on the other hand, we believe that showing the current conditions of a large number of buildings used for different activities allows the reader to have a clearer idea of the capabilities that the incorporation of natural ventilation currently offers in terms of air quality in these buildings and the importance of having considered this possibility in their design.

The reviewer's consideration of the need to clearly incorporate the objective of the study and its novelty in its field of research is entirely correct. Consequently, this idea has been incorporated into both the abstract and the conclusions, clearly establishing the novelty in this field of research:

• In the abstract section:

…and limit airborne disease transmission. Natural ventilation can be incorporated into building design as the primary mechanism for achieving the required indoor air quality, equipping buildings with operable windows based on their intended occupancy. Using eleven public…

• In the conclusions section:

…to maintain IDA2 air quality [44, 45].

To this end, a methodology is presented that allows the design of more sustainable buildings, incorporating the possibility of establishing natural ventilation as the main mechanism for obtaining the desired indoor air quality, by providing an openable surface in the building's windows, depending on the expected occupancy.

It was also observed that the model developed…

Similarly, the ventilation parameters considered for this research are set out more clearly. As a result, the following paragraph has been added:

Value similar to the 45 m³/h per person required by regulations to consider air quality IDA2 (RITE).

Considering this value as a reference threshold, the classic action levels are established, as a methodology in Industrial Hygiene, at 75%, 50% and 25% of this limit, i.e. 15.62 l/s, 18.75 l/s and 21.87 l/s. Consequently, the reference values for ΔCO2 are, respectively, 230 ppm, 270 ppm and 320 ppm. Assuming an outdoor concentration of between 400 ppm and 500 ppm, the reference values indoors will be 730 ppm, 770 ppm and 820 ppm.

The authors agree with the reviewer that the inclusion of a flow chart to facilitate understanding of the proposed calculation method is entirely appropriate and relevant. Therefore, the following diagram has been added to the paper, along with some introductory text:

The calculation process consists of three phases. First, the required air quality is established. Second, the ventilation flow rate per person necessary to achieve the previously established air quality is determined. Finally, the occupancy that allows these conditions to be met based on the available natural ventilation is determined (Figure 4).

Figure 4. Flowchart process diagram.

As an example of an application that facilitates understanding of the results tables (Tables 10 to 18):

The Plenary Hall is located on the third floor of the Town Hall building. The occupancy that allows IDA2 air quality with all windows open on both sashes is 20 people (Table 8). The room is designed for 77 people. The IDA2 occupancy relative to the design occupancy is:

 

The authors agree with the reviewer that it would be beneficial to include a discussion of the results to enable the reader to interpret the data and tables presented. Therefore, the following text has been added to the paper:

Table 10 shows that 70% of the locations with the possibility of natural ventilation in the Citizen Participation Centre / Junta I building allow for IDA2 air quality to be achieved.

Table 11 shows that 22.2% of locations with natural ventilation potential in Town Hall building allow IDA2 air quality to be achieved.

Table 12 shows that none of the locations with natural ventilation potential in the Junta 4 West building allow IDA2 air quality to be achieved.

Table 13 shows that despite having cross ventilation in the adult room, study room and youth room, which are designed to accommodate a very large number of occupants, it is not possible to maintain adequate air quality by opening the windows alone.

Table 14 shows that it is not possible to maintain adequate air quality at the Rodolfo Halffter Conservatory with the available operable windows.

Table 15 shows that the Kaleidoscope Sociocultural Centre/El Soto/Villa de Mostoles centres only have cross ventilation in the library, and their high occupancy levels prevent adequate air quality from being achieved with natural ventilation alone.

Table 16 shows that the Ramón Rubial Social Centre is located on the ground floor of a residential building and, although it has casement windows, these are small and do not allow for cross ventilation.

Table 17 shows that the first floor of Ribera Youth Space is located on the ground floor of a residential building and has casement windows, but these do not allow for cross ventilation.

As demonstrated in Table 18, the General Services building is a single-storey structure with casement windows. However, these windows permit cross ventilation exclusively within the administration area.

For this reason, the following paragraph and a floor plan of the General Services building have also been included in the paper, as author(s) believe it will be useful for de reader's understanding.

The General Services building is a single-storey building with casement windows, but these only allow cross ventilation in the administration area (Figure 3).

 

Figure 3. Ground floor plan of the General Services building.

 

 

 

 

 

 

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

While the paper is somewhat improved, the writing is still in need of heavy editing and revision. 

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript can be ACCEPTED and can be published.

Reviewer 4 Report

Comments and Suggestions for Authors

Dear Authors,

please modify editing following journal guideline.