Characteristics of Mould Growth in Pine and Spruce Sapwood and Heartwood under Fluctuating Humidity

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript delves into the nuances of mold proliferation on the sapwood and heartwood of pine and spruce, subjected to varying conditions of humidity and temperature. This investigation is pertinent to the realms of indoor environmental health and the enduring integrity of construction materials. 

1.The universality of the research results needs further verification. It is suggested that the author consider the growth of wood fungi in different regions and under different climatic conditions to enhance the applicability of the research results.

2.The experiment spanned a duration of five months; however, there is no explicit discussion on the contemplation of long-term stability. It is recommended that the author elaborate on how the chosen experimental timeframe influenced the findings and to deliberate on the necessity of extending the observational period for a more comprehensive assessment.

3.The manuscript would benefit from clarification on the inclusion of a control group. Specifically, it would be advantageous to know if there was a comparative setup under stable humidity and temperature conditions, which could serve to accentuate and quantify the distinctive impacts of fluctuating environmental parameters on mold proliferation.

4.While the paper furnishes a wealth of detailed observational data, it falls short of incorporating statistical analysis to substantiate the significance of the findings. It is recommended that the author employs pertinent statistical methods to affirm the robustness and validity of the results.

5.The discussion section could benefit from an in-depth exploration of the underlying mechanisms that contribute to the experimental outcomes, as well as an integration of these results within the context of existing literature and prevailing theories. Furthermore, while the paper does include some illustrative images, the addition of comprehensive charts would enhance the visual representation of mold growth trajectories over time and across varying experimental conditions.

 

Comments on the Quality of English Language

This paper is a study on the growth characteristics of fungi on the sapwood and heartwood of pine and spruce trees under different humidity and temperature fluctuations. From the provided content, it can be seen that the paper uses professional terminology and follows the format and style of academic writing. However, there are also some areas that may need improvement:

1. In some cases, there may be minor grammar and spelling errors in the text, such as "revised" being "verified", "Indoor" "Indoor", and possible improper use of punctuation.

2. Consistency of terminology * *: It is important to ensure consistency of professional terminologies, such as "mold" and "mold", which should be used uniformly in the text.

Author Response

Comments 1 [1.The universality of the research results needs further verification. It is suggested that the author consider the growth of wood fungi in different regions and under different climatic conditions to enhance the applicability of the research results.]

Answer:

Yes you are right, we want to include wood decaying fungi and the effect of conditions on their growth as further research. Unfortunately, all of these experiments are long-term and our funding only allows us to do research in small parts

Comments 2. The experiment spanned a duration of five months; however, there is no explicit discussion on the contemplation of long-term stability. It is recommended that the author elaborate on how the chosen experimental timeframe influenced the findings and to deliberate on the necessity of extending the observational period for a more comprehensive assessment.

Answer:

The experiment actually lasted about two months longer, but the evaluation was extended to once every 14 days for the last few months because the mould growth was no longer changing. For this reason, I no longer present the results in the article. My original assumption that new mold would grow from the newly formed spores has not been confirmed. This happened probably because the moulds were not in contact with the wood, hence they did not have available nutrients.

Comments 3.The manuscript would benefit from clarification on the inclusion of a control group. Specifically, it would be advantageous to know if there was a comparative setup under stable humidity and temperature conditions, which could serve to accentuate and quantify the distinctive impacts of fluctuating environmental parameters on mold proliferation.

Answer:

This research followed a study under constant conditions which showed a slight difference between mould growth on uniform samples according to the direction of the wood fibres, since changing conditions did not confirm this difference is not discussed. It might be worthwhile to extend the discussion somehow to this aspect as well. 

Comments 4 While the paper furnishes a wealth of detailed observational data, it falls short of incorporating statistical analysis to substantiate the significance of the findings. It is recommended that the author employs pertinent statistical methods to affirm the robustness and validity of the results.

 Answer:

I tried to do a statistical analysis, but unfortunately this is not my strong domain. My efforts have not yielded usable data.

 

Comments 5.The discussion section could benefit from an in-depth exploration of the underlying mechanisms that contribute to the experimental outcomes, as well as an integration of these results within the context of existing literature and prevailing theories. Furthermore, while the paper does include some illustrative images, the addition of comprehensive charts would enhance the visual representation of mold growth trajectories over time and across varying experimental conditions.

Answer:

Regarding mould growth on wood, the biggest problem is that in the articles on this topic each group uses a different definition of the Mould Index and different conditions (RH range, T range, different mould consortium). All my assumptions as to why a given growth was visible are not supported by the literature and every time I write them in an article the rewierer forces me to look for support in the literature. We have tried to create a table of results from published graphs with the same definition of MI as we understand, but the results across authors are quite different.

 

Reviewer 2 Report

Comments and Suggestions for Authors

The article presented, concerning the attackability of wooden surfaces by mould, concerns an experiment whose conditions and procedures have been well defined. However, the article has some errors and lacks some aspects according to the indications provided below point by point.

 

Lines 9 and 10

There is no “number 2” in the authors’ references. Then, these lines must be deleted.

 

Lines 13 and 14

In the introduction Authors refer to timber building. In EUROCODE5 the durability of timber structures depends on service class of the buildings. For indoor climate is expected the service class 1 or 2 (SC 2 relative humidity higher than 85% only for few weeks for year). If you desire to refer to building problems, perhaps you should contextualize a little better the problems of mould on indoor, also because the conditions indicated are not at all suitable for a pleasant living condition for the inhabitants of the building. They are more relevant to design errors or unforeseen events.

 

LINES 92 and 93

A very great mistake is present: your sapwood specimens are cut from heartwood! It is a very big error. You must decide if you want to sample sapwood or heartwood.

 

LINES 99 and 100

The motivation to use specimens cut in the different anatomical direction of wood is not explained. Reasons and motivation are necessary. Since your specimens come from different cuts of wood, it is important to consider that the cross cut is much more sensitive to the change of RH (relative humidity), and quick to reach the EMC (equilibrium moisture content), while the other 2 cuts are slower. The reason is principally anatomical because in the transversely cut sample the exchange surfaces with the air are much larger, thanks to the transversely cut tracheids.

 

LINES 101, 102 and 103

You are going to explain materials and methods, while in these lines it seems you want to anticipate some result aspects.

 

LINES 103 and 104

It might be helpful to refer to the paragraph the sentence refers to.

 

Line 116

The statement that the boards are resin-free, needs to be rewritten, since both spruce and pine contain resin channels that are still full of resin at the time of felling. The authors probably mean something else, which must be explained.

 

LINES 122 and 123

Creation is a divine prerogative. You just cut the specimens to size. To be corrected.

 

TABLE 1

Some mistakes in the table:

- in the description,

- inside the table PsX and SsX are repeated also in the heartwood

- the meaning of “sapwood 3” is not clear.

To be corrected.

 

TABLE 1 

General comment about the sampling:
For the research you produced several sets of specimens. To complete the work it would have been important to know the actual starting and final moisture content through the EN 13183-1 standard testing, preparing for this purpose 4 or 6 special specimens to be sacrificed.

Figure 2

The graphic quality of the figure is very low. A higher resolution image is needed.

 

LINES 133 and 134

It seems to me that the environmental conditions established have not any reference standard. Did you use EN ISO 483? What kind of standard indicates that Na2SO4 reaches 86% of RH?

 

LINES 148 and 149

It is indicated the 1D transport. The authors should better explain the reasons for this choice, even if correct.

 

LINES 161-164

According to the standard ISO 483 it seems that a saturated NaCl solution at the box temperature of 15°C reaches another RH. Some bibliographic references regarding the environmental conditions are necessary.

 

FIGURE 4 and 5

While the way to control RH is indicated, there are not indications concerning the temperature control. Since the graphic is showing a very precise control of T and RH, some information concerning the functioning system of the box is needed.

 

LINE 197, 204,

Fibbers?

To be corrected.

 

LINES 199-201

“Spruce sapwood”? but the chapter is titled Spruce heartwood

 

LINE 213

(101) …. (110) …. (120)….  The meaning of these numbers are unintelligible.

 

 

TABLES 4 and 5

It is not clear enough how the indices are calculated: the average of 6 specimens?, the worst?

A clear explanation of the index calculation is needed.

 

LINE 273

The definition of spp. doesn’t seem correct.

Spp. stands for “species plural” and means we're talking about multiple species in the same genus.

Author Response

Comment 1 

Lines 9 and 10 There is no “number 2” in the authors’ references. Then, these lines must be deleted.

 

Answer:

Thanks you, this is my first time working with Latex and I didn't notice it

Comment Lines 13 and 14

Yes you are right the conditions mentioned are not ideal for living in buildings, but they were chosen because they are suitable for mould growth. In our field research we often find degradation of wooden structures not only with wood-deccaying fungi, but also very high levels of mould. We have had to limit the conditions somehow in first round. In further research we have already set up conditions closer to those found in real buildings. 

Comment LINES 92 and 93

Thanks my mistake

Commnet LINES 99 and 100 (motivation)

Yes, you're right. We assumed exactly the reason you gave for the difference in diaper growth, which was confirmed under constant conditions. The main motivation was to see how much influence anatomical directions have on fungal growth. Unfortunately, it was probably a mistake to use such thin samples where the development was established quickly.

Comment LINES 101, 102 and 103, LINES 103 and 104, Line 116, LINES 122 and 123

I have rewritten and added these parts to make it more understandable

Commnet TABLE 1

Thanks you, this is my first time working with Latex and I didn't notice it

Comment General comment about the sampling

Yes it would probably be good, since we were continuing with a similar experiment that modeled moisture transport, I preferred to add samples inoculated with mould. I will keep this in mind in future experiments.  

Comment Figure 2

Yes you're right, I'll track down the original pics and create a new one. 

Comment LINES 133 and 134

I have checked the humidity over Na2SO4 x 10 H2O and the tables indicate a humidity of about 86% and we achieve this humidity in our other experiments. Since this humidity was used to condition the samples before the experiment so that all samples start at the same conditions, I saw no reason to address the leading number. The humidity was chosen to be approximately the midpoint between the ocarajor conditions of the experiment.

Comment LINES 148 and 149

The experiment was related to the moisture and heat transport measurement experiment and therefore the sample locations were chosen to apply both results to the mould growth model. I have added a note to the paper. 

Comment LINES 161-164

I checked again the stability of the moisture produced by the NaCl saturated solution as a function of temperature and the resulting RH is quite stable. This is based on our previous experiments and the literature e.g. L. Greenspan, “Humidity Fixed Points of Binary Saturated Aqueous Solutions”, Journal of Research of the National Bureau of Standards - A. Physics and Chemistry, 1977, 81A (1) pp. 89-96

 

Comment FIGURE 4 and 5

All information of box are punlishe at other publication. Richter J, Staněk K, Kopecký P, Schůtová P, Tywoniak J. Dynamic moisture transport in spruce wood–Experiment in hygroscopic 361
range under isothermal conditions. In: AIP Conference Proceedings. 

Commemt LINE 197, 204, LINES 199-201

Thanks

Comment LINE 213

I've rewritten it for ease of understanding

Comment TABLES 4 and 5

I've added some notes for ease of understanding

Comment LINE 273

Thanks

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript offers a wealth of valuable data and keen insights into the behavior of fungal growth on wood under fluctuating environmental conditions. Employing rigorous scientific research methods and a thorough analysis of the results, the study makes a notable contribution to the field of architectural science. 

Suggestion:

1. The author may consider further exploring the specific effects of different wood chemical compositions on mold growth.

2. The impact of research results on practical applications can be more widely elaborated. Exploring how to effectively integrate these insights into the fields of building maintenance and indoor environmental quality management would be beneficial.

Comments on the Quality of English Language

Minor editing of English language required.

Author Response

We are grateful for your valuable suggestions, some of which we have already used in our ongoing research.
Some variables were only identified during the experiment and data analysis, and were no further included in the research. We are currently running a semi-real experiment to develop more accurate models and information that could be incorporated into the building maintenance field.

Reviewer 2 Report

Comments and Suggestions for Authors

Please, compile again the "answers to the reviewer" including also the original comments of the reviewer, like it is usual!

This is the only way to check your answers to the reviewer's comments.

Thank you.

Author Response

Thank you for your help. I have incorporated all the revisions and put the answers into the documnet

Author Response File: Author Response.pdf