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Peer-Review Record

Impact of Water-Repellent Products on the Moisture Transport Properties and Mould Susceptibility of External Thermal Insulation Composite Systems

Coatings 2021, 11(5), 554; https://doi.org/10.3390/coatings11050554
Reviewer 1: Antonella Curulli
Reviewer 2: Anonymous
Reviewer 3: Anonymous
Coatings 2021, 11(5), 554; https://doi.org/10.3390/coatings11050554
Received: 6 April 2021 / Revised: 1 May 2021 / Accepted: 5 May 2021 / Published: 8 May 2021
(This article belongs to the Special Issue Advanced Coatings for Buildings - Challenges and Opportunities)

Round 1

Reviewer 1 Report

The paper is interesting but on my opinion requires a study of the effects coming from other degradation agents such solar radiation, UV exposure, pollutants so obtaining a clearer view on the degradation of ETICS  during time.

In my opinion, I suggest  amore deeper study of the degradation of ETICS non including only the water effects, but also considering the effects of pollutants, solar radiation, freeze-thaw cycle. All these info can be obtatined using methods and devices for aging tests, it is a normal procedure and protocol to investigate the building materials behaviour during time. 

Author Response

1. The paper is interesting but on my opinion requires a study of the effects coming from other degradation agents such solar radiation, UV exposure, pollutants so obtaining a clearer view on the degradation of ETICS during time.

I suggest a more deep study of the degradation of ETICS non including only the water effects, but also considering the effects of pollutants, solar radiation, freeze-thaw cycle. All these info can be obtained using methods and devices for aging tests, it is a normal procedure and protocol to investigate the building materials behaviour during time.

This paper intends to compare the moisture transport properties and mould susceptibility of three commercial hydrophobic products. It is worth noting that a proper analysis of the moisture transport properties can indirectly provide useful data also on other physical properties of the aged/unaged treated/untreated specimens, as reported also in the manuscript.

This paper focuses also on the hygrothermal aging of ETICS specimens with hydrophobic products. A more complete aging protocol, which includes artificial aging with UV lamps and climatic chambers with pollutants (SO2, NOx), has been already considered and partially developed by the authors. Preliminary results confirmed that ETICS are mostly affected by hygrothermal cycles, whereas a rather lower impact was identified with UV and pollutants. These considerations reinforce the importance of this study, i.e. the hygric and physical durability of the systems to the combined effect of water and thermal gradients.
It is worth noting that authors are also verifying the durability to natural aging of the ETICS specimens. However, those results are out of the scope of this paper and will be presented in future publications.

Reviewer 2 Report

  1. It is not advisable to have a shortened form in the title (abbrevation)
  2. Water absorption in materials create internal stresses. A small cracks produced by these stresses will propagate over time and result in failure. This is not mentioned at all in the introduction; while other factors have been mentioned.
  3. Anyone following the article should be able to reproduce the work. With this in mind - material section should be elaborated (2.1.1 and 2.1.2)
  4. Page 3, line 110 - error
  5. 2.2.1 and 2.2.6 section several errors for reference
  6. Refererence errors in result section - Authors are advised to check the reference before submission - there are reference errors throughout the document
  7. When the water repellent was the main aim of the work - why authors did not aim for higher contact angle
  8. Hard to see the difference in micrographs between before aging and after aging

It is important that the authors go through the entire manuscript for references

Author Response

1. It is not advisable to have a shortened form in the title (abbrevation)

As suggested, the acronym (ETICS) was deleted, using the extended word. Additionally, the title was slightly modifie.

2. Water absorption in materials create internal stresses. A small cracks produced by these stresses will propagate over time and result in failure. This is not mentioned at all in the introduction; while other factors have been mentioned.

This further comment on internal stresses created by Water absorption was added in sections 3.1, as suggested; a reference on this topic [20] was also added in the text.

 3. Anyone following the article should be able to reproduce the work. With this in mind - material section should be elaborated (2.1.1 and 2.1.2)

If the reviewer intends that sections 2.1.1 and 2.1.2 should mention the commercial names of the used ETICS and hydrophobic products, it should be said that it is out of the scope of this paper the promotion or rejection of specific products. On the other hand, these two sections provide specific informations (physical-chemical composition and properties) that can help other authors to understand and study the effectiveness and durability of products with similar characteristics, which represent a large part of the commercially available hydrophobic products.

On the other hand, a short sentence was added in section 2.2.2, in order to describe more in detail the preparation of the specimens.

 4. Page 3, line 110 – error

It was corrected, accordingly

 5. 2.2.1 and 2.2.6 section several errors for reference

Errors related to references//figures/tables were corrected, as suggested.

6. Reference errors in result section - Authors are advised to check the reference before submission - there are reference errors throughout the document

Errors related to references was corrected, as suggested.

7. When the water repellent was the main aim of the work - why authors did not aim for higher contact angle

As specified in section 3.3, the application of hydrophobic products was expected to provide a considerable improve of the contact angle. However, even a reduction was observed in the case of H1, and only a slight improvement in the case of H3. Only product H2 provided a significant θ increase, when compared to the untreated-reference specimen. It was explained that this behavior can be related to the composition of the products, i.e. the inclusion of hygroscopic non-polymeric additives (e.g. carbonates), as well as TiO2, which have typically hydrophilic properties. It is worth noting that these products are not only hydrophobic products, but rather multifunctional paints, which can also exhibit biocide and self-cleaning properties (as specified in section 3.3).

8. Hard to see the difference in micrographs between before aging and after aging

 The figure was modified in order to improve the comprehension and differences among the different images.

9. It is important that the authors go through the entire manuscript for references

Errors related to references were corrected, as suggested.

Reviewer 3 Report

The authors should correct the manuscript in order for the references to be valid and resubmit.

Author Response

1. The authors should correct the manuscript in order for the references to be valid and resubmit.

References were controlled and corrected, as suggested.

Round 2

Reviewer 1 Report

1. Considering the autors comment, I suggest to accept the paper in the present form

The authors acknowledge the review for the suggestions/corrections.

Reviewer 2 Report

1. All the comments are addressed

The authors acknowledge the review for the suggestions/corrections.

Reviewer 3 Report

1. The manuscipt entitled " Influence of water-repellent products on the moisture transport properties and mould susceptibility of ETICS" present the findings of the effect of  commercial hydrophobic products on ETICS. After reviewing the document I do not recommend it's publication in the present form. My main objection is that the results are not supported/explained in a  solid scientific manner. The manuscript will benefit if the authors correlate their findings with determined material properties (e.g. pore size distribution) instead of speculating.  

This paper intends to compare the moisture transport properties and bio-susceptability of the three commercial products. It is worth noting that a proper analysis of the moisture transport properties can indirectly provide useful data also on other physical properties of the aged/unaged treated/untreated specimens, as reported also in the
manuscript.
Although further analyses (e.g. pore size distribution, BET) will be interesting to further correlate the interaction of the hydrophobic products with the treated substrates, no porosimetric analysis was finalized at this point of the research. These analyses are partially ongoing, within the framework of a wider national project. This latter aspect was further specified in the conclusions.
It is worth noting that the porosimetry analysis (mercury intrusion porosimetry and/or Brunauer-Emmett-Teller surface area analysis) of a composite, multi-layer system is a complex task that required also several weeks, in order to be planned, finalized and analysed.

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