Energy Cost for Effective Ventilation and Air Quality for Healthy Buildings: Plant Proposals for a Historic Building School Reopening in the Covid-19 Era

Round 1

Reviewer 1 Report

In general, the English style should be reviewed. Especially, authors should watch out for excessive sentence size and abusive use of commas. It is difficult to follow the reading. They should use each sentence to convey a single idea, and the paragraph for a single message.

I recommend to rephrase the second part of the title.

The recommended structure of the abstract by the editorial of the journal should be followed. For this, authors should place the question addressed in a broad context and highlight the purpose of the study. Then, they should describe briefly the main methods or treatments applied. Next, they should summarize the article's main findings. Finally they should indicate the main conclusions or interpretations.

The concepts of sustainable and environment should be better presented. Besides, it is not clear whether there is a flow (energy sustainability → health (people and environment) → sustainability (energy and environment). Efficiency is not mentioned. Energy consumption neither.

First it would be necessary to demonstrate the technical feasibility of intervening a use in a building. Then, if there is more than one possibility, evaluate which is the best proposal attending a series of criteria (for example, the economic one).

The introduction should briefly place the study in a broad context and highlight why it is important. It should define the purpose of the work and its significance. The current state of the research field should be reviewed carefully and key publications cited, highlighting controversial and diverging hypotheses when necessary.

For that, the problem to be solved in the article should be more clearly stated.

When authors hold "effective ventilation, hygiene, safety and health", they should stress the renovation and decontamination.

Superintendency for Cultural Property is an Italian Public Administration (organization). The Italian context is not properly introduced. 

A series of constructive and thermal characteristics are defined for Italian Historic Buildings but no reference is included. This generalization should be put into context.

Totalitarian phrases such as "is never enough" should be avoided. Never is too ambitious by detracting from the rigour of the rest of the discourse.

If a useful prediction model is provided by authors, this must be relevant in order to be included in abstract or even the title, but those one do not mention it.

Are the authors sure that sustainable, non-invasive, reversible and conservative measures are compatible? Are they equally important?

The concept of "transition phases" should be explained.

The main objective should be better defined (S.M.A.R.T.) in order to check the degree of alignment of the processes developed.

A lot of sanitary alerts are introduced but only aire renovation (ACH), indoor air temperature, relative humidity and velocity are considered at the end. Most of them are related to confort (which was sacrificed previously if required).

Nothing about filters (such as HEPA filters) is mentioned.

When energy efficient, effective and sustainable operations are considered nothing about health is highlighted (healthcare operations for example).

The parameters and previous conditions that are not valid in this pandemic context are not well defined. How to change them? 

Climatic data should be better explained. The station is close to the building and their climatic data are assumed.

But, only one year has been chosen? Which one? Shouldn't it have been taken, at least the last available TMY contemplating at least 10 years? TRY? Real Data?

If decisions are taken from these data this question should be enlightened.

The case study (the building) should be better explained in order to follow authors when are explaining climatized and non climatized zones.

"Most literature on the subject, indicates that in the post-Covid era, people density must be cut at least by 50%, in comparison to pre-Covid management"...ok but which ones? Is this situation temporary or permanent? Idem with the opening time. In order to simulate, conclusions can be aligned with this provisional situation or for next years in order to be prepared for the same or other singular (and future) situations.

Opaque components: facade, roof, groudfloor...2.0 W/m2K? All these elements? A bit poor...All the transparent components 5 W/m2K? Terrible

With these data, the envelope should be rehabilitated, right?

How is natural ventilation modelled (simulated) by manual infiltration and opening?

8 settings of HVAC management should mean 16 study cases, right?

8 settings with the original envelope, and other 8 with the new envelope.

Which European countries are considered? Firenze should be compared with other analogue cimates.

...

The article should be rewritten in its entirety, in order to lose confusion and gain clarity and even rigor.

This paper and begins referring to covid-19 pandemic but the process is aligned with the improvement of the energy saving and not considering as the first factor (perhaps it could be made by a multicriteria decision AHP) the wellbeing and health of people.

A minimum healthy requirements should be planned. And only to consider those scenarios that fulfill them. Among them, to compare saving could be interesting. But the first problem is to adapt an historic building to the pandemic context.

Author Response

Answers to Reviewer 1

The authors thank the Reviewer for the revision and for the time devoted to it. The authors took into account all the Reviewer’s comments and suggestions. The corrected parts of the revised manuscript are highlighted in yellow. The specific answers to Reviewer 1, follow:

1. The lengthy sentences have been checked and shortened. The whole text of the manuscript has been checked again for grammar and style by a native English speaker a professor, at our University who has considerable experience in revising technical English texts.

1. The second part of the title has been rephrased as suggested by the reviewer.

1. Referring to the reviewer’s comment, the abstract has been rewritten and improved, highlighting the aim of the research, materials and method used and main results obtained.

1. Taking into account the reviewer’s comment, the concepts of sustainability and environmental quality have been better explained, referring to the fundamental concepts of efficiency/energy saving as well as indoor air quality/environmental, quality/healthy environment and considering their technical/practical feasibility. Both in the abstract and introduction section the written text concerning this issue has been modified and improved (all these changes have been highlighted in yellow).

1. Taking into account the reviewer’s comment, the introduction section has been improved and extended. As a consequence, the background on the research field has been carefully reviewed and the key publications have been cited. Then, the main objective of the research has been more clearly stated.

1. Considering the reviewer’s comment, the main objectives of the proposed and investigated plant solutions i.e. effective ventilation, hygiene, safety and health have been better explained, considering the renovation and decontamination issues.

1. The reference to Superintendency for Cultural Property, i.e. Italian Public Administration (organization), has been checked and written only in the part of the manuscript to which it refers.

1. Considering the reviewer’s suggestion, the constructive and thermal characteristics defined for Italian historic buildings have been put in a general context referring to the added literature references.

1. All the hyperbolic phrases such as “never enough” have been deleted and new improved and clearer statements have taken their place.

1. No prediction model has been considered or suggested by the authors. The written parts of the manuscript that could create this misunderstanding have been corrected and verified.

1. Referring to the reviewer’s comment, the concepts of sustainable, non-invasive, reversible and conservative measures, have been clarified. So that the main research object has also been clarified.

1. As suggested by the reviewer, the concept of “transition phases” has been better explained and the sentences it refers to have been modified.

1. Taking into account the reviewer’s comment, the main aim of the proposed design solutions concerning indoor air quality and healthy environment for occupants has been better explained in comparison to building-plant system energy renovation (i.e. retrofitting/refurbishment).

1. Controlled mechanical ventilation solutions have been better explained referring to the absolute air filtration system used (i.e. considering HEPA filters). Then all the questions relating to health have been closely connected to the efficiency and effectiveness of the various plant solutions assessed.

1. All the parameters and previous conditions referring to the existing building and its plant system (i.e. the reference case) and the possible/feasible changes have been clarified.

1. Taking into account the reviewer’s comment, climatic data used have better explained. The TRY has been better explained and its utilization for transient simulations has been clarified. Furthermore, the use of real climatic data provided by LAMMA, to  make the corresponding real Heating Degree Days (HDDs) used for simulation model validation, has been defined and better explained.

1. Taking into account the reviewer’s comment, the building case study has been better defined, explaining the standard method used to identify the climate-controlled and no climate-controlled zones.

1. Considering the reviewer’s comment, current indications and guidelines on people density reduction and the social distance issue have been included in the corrected sentence. In particular, the word “post-Covid era” was a typing error and it has been corrected checking all the written text of the manuscript.

1. Taking into account the reviewer’s questions, all the thermo-physical properties of building materials of the existing/reference case have been better identified and the possible rehabilitation measures better explained.

1. Considering the reviewer’s question, the simulation of natural ventilation conditions have been better and clearly explained. Also the different settings of HVAC management have been better explained.

1. Taking into account the reviewer’s comment, on page 8 lines 333-336, the sentence has been corrected and the concepts discussed better explained and argued, referring to the main literature on the matter.

1. For the most part the manuscript has been completely rewritten, improved and extended.

1. Taking into account the reviewer’s comment, the fundamental findings of our research that is a plant project aimed at efficiency and effectiveness, based on the compromise solution between energy saving and IAQ, health and safety of people, has been better clarified and highlighted.

1. Referring to the reviewer’s comment, further development of our study, concerning the assessment of different scenarios of combined operations oriented to health requirements in relation to connected energy consumption, has been provided and discussed.

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper presented by Carla and Lorenzo examined the effectiveness of plant retrofit on controlling indoor air quality in a historic school building. The topic is of great interest under the current situation of reopening during the Covid-19 era. The paper is overall easy to follow. A few comments for the authors to consider as follows:

1. Too many lengthy sentences in the paper. Please polish the English writing of the paper.
2. Do the authors have any cases or references to support the accuracy of the transient simulation?
3. A high air change rate without air recirculation means that the ventilation can also potentially introduce more air pollutants from outdoor into the classroom. Outdoor air is not always clean. What is the authors’ consideration of this issue?
4. Energy retrofitting of houses could increase occupants’ exposure level to certain air pollutants, if not compensated with adequate ventilation. It is worth mentioning in the Introduction or Discussion section. Some examples:

Yang, S., Pernot, J. G., Jörin, C. H., Niculita-Hirzel, H., Perret, V., & Licina, D. (2020). Energy, indoor air quality, occupant behavior, self-reported symptoms and satisfaction in energy-efficient dwellings in Switzerland. Building and Environment, 171, 106618.

Niculita-Hirzel, H., Yang, S., Hager Jörin, C., Perret, V., Licina, D., & Goyette Pernot, J. (2020). Fungal Contaminants in Energy Efficient Dwellings: Impact of Ventilation Type and Level of Urbanization. International Journal of Environmental Research and Public Health, 17(14), 4936.

Yang, S., Perret, V., Hager Jörin, C., Niculita‐Hirzel, H., Goyette Pernot, J., & Licina, D. (2020). Volatile organic compounds in 169 energy‐efficient dwellings in Switzerland. Indoor air, 30(3), 481-491.

Author Response

Answers to Reviewer 2

The authors thank the Reviewer for the very careful revision and for the time devoted to it. The authors took into account all the Reviewer’s comments and suggestions. The corrected parts of the revised manuscript are highlighted in yellow. The specific answers to Reviewer 2, follow:

1. The lengthy sentences have been checked and shortened. The whole text of the manuscript has been checked again for grammar and style by a native English speaker, a professor at our University, who has considerable experience in revising technical English texts.

1. Taking into account the reviewer’s comment, the validation method applied to check the simulation model accuracy has become more explicit.

1. Considering the reviewer’s suggestion, the issue concerning the plant retrofit solutions based on a controlled mechanical ventilation system with high air change rate, but without air recirculation, is now clearer foregrounding the basic choice for absolute air filtration (i.e. considering the HEPA filters use).

1. Taking into account the reviewer’s comment, the introduction section has been improved and extended. As a consequence, the background on the research field has been carefully reviewed and the suggested key publications cited.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Well done.

The paper has been deeply improved.

My comments and suggestions have been attended.

Now I believe can be published.