Review Reports - Straw Bale Building as a Low-Tech Solution: A Case Study in Northern Poland

Round 1

Reviewer 1 Report

1. What is the novelty of the paper?

2. What is the added value of the paper?

3. The resolution of the Figures 7, 8, 9 and 16 is very low.

4. Insert a flow chart for your research.

5. The figures are numbered incorrectly.

6. In the section "Results", are presented the Figures (18, 18, 19, 20, and 21), that do not belong to the author.

Figure 18. Thermal imaging photo of the south side of the building - a section of the wall under the roof eaves. No visible thermal bridges. Source: thermal imaging inspection report [33].

Figure 18. Thermal imaging photo of the south side of the building - a section of the wall under the 386 roof eaves. Visible Thermal Bridges - exterior window frames and glazing spacers. Source: thermal 387 imaging inspection report [33].

Figure 19. Thermal imaging photo of the north side of the building - a section of the wall under the 393 roof eaves. Visible leaks both in the plaster and at the joint of the eave beams, as well as gaps be- 394 tween the roof slab and the wall. Source: thermal imaging inspection report [33].

Figure 20. Thermal imaging photo of the north side of the building - a section of the wall under the 397 roof eaves. Visible leaks both in the plaster and at the joint of the eave beams. Source: thermal im- 398 aging inspection report [33].

Figure 21. Thermal imaging photo of the north side of the building. Visible leaks both in the plaster, 401 as well as at the connection of the cap beams, and gaps between the roof slab and the wall. Sp2 is an 402 inadequately sealed cable entrance to the wall measurements. Source: thermal imaging inspection 403 report [33].

7. The author should refine the “Discussion” chapther.

8. All the data presented in the "Results" chapter must be analyzed in the "Discussions" section.

9. The experimental results obtained must be compared with the results presented in the literature (in tabular for).

10. The author should refine the abstract and the conclusions.

11. The "Conclusions" chapter is missing.

Comments for author File: Comments.pdf

Author Response

Thank you very much for your review and valuable comments!

All of the comments were taken into account. In addition, comments from other reviewers were taken into account. Below I answer the questions. In addition, I have prepared a list of changes that includes changes after comments from all reviewers (1-list_of_changes).

Kind Regards

What is the novelty of the paper?

Of course, the analyzes of the U-value and the condensation risk are nothing new. Strawbale technology is becoming more and more popular in Western countries as well as Central and Eastern Europe. Until now, there has been little critical analysis of this type of building, especially in a northern climate. There are few publications on this subject, and they mainly concern locations in a warmer climate than the one analyzed in this article. I think this analysis may be an interesting voice in the discussion for some strawbale interested.

What is the added value of the paper?

As mentioned earlier - analyses of this type in cold climates with frosty winters like the one in northern Poland. The analysis of the straw thermal conductivity coefficient is also interesting, as you can see the parameter depends on many factors and is different in individual sources. Therefore, it can be assumed that when designing in Poland, with the assumption of thermal insulation at the construction site, they should rather take values worse than those assumed by other researchers. This is of great importance for the energy standard of the entire building. Similarly, air tightness. Rather, low values of the N50 air tightness coefficient should not be assumed.

The resolution of the Figures 7, 8, 9 and 16 is very low.

As suggested, I corrected Figures 7, 8 and 9 and also 16 (In the new version, these are 10, 11,12 and 19).

Insert a flow chart for your research.

The flowchart would be relatively simple here, I'm not sure if it is necessary. I am enclosing the prepared flowchart. Please let me know whether to include it in the article?

5.The figures are numbered incorrectly.

Yes, that's right, the wrong numbering has been corrected.

In the section "Results", are presented the Figures (18, 18, 19, 20, and 21), that do not belong to the author.

Figure 18. Thermal imaging photo of the south side of the building - a section of the wall under the roof eaves. No visible thermal bridges. Source: thermal imaging inspection report [33].

Figure 18. Thermal imaging photo of the south side of the building - a section of the wall under the 386 roof eaves. Visible Thermal Bridges - exterior window frames and glazing spacers. Source: thermal 387 imaging inspection report [33].

The indicated photos - I have given the source for this, where the author is also located. I own the copyrights. The author has been added.

The author should refine the “Discussion” chapther.

The chapter discussion has been shortened. Part of the text has been moved to the new chapter Conclusions.

All the data presented in the "Results" chapter must be analyzed in the "Discussions" section.

A section on air tightness testing of strawbale buildings has been added to the discussion chapter.

The experimental results obtained must be compared with the results presented in the literature (in tabular for).

I tried to calculate the thermal conductivity ( which I estimate 0.085 for bales of straw. But I cannot list it in Table 1 because the in-situ calculations were made for a heterogeneous face. The wooden structure also influences the result. For this reason, I have reservations about including these results in Table 1.As suggested, the straw thermal conductivity coefficient has been inserted in Table 1 as a result of the U coefficient of the walls (last item). However, this is an approximate value because when measuring the U-value of a wall, the measurement is also influenced by the wooden structure. The position of the heat-flux sensor was between the bars, where the influence of the bars is the smallest. On this basis, an approximate value of the thermal conductivity coefficient λ of straw was calculated.

The other results cannot be summarized in a similar way - in the case of the moisture content, other authors did not use the Minke’s formula, but determined based on the limit values of the relative humidity. The climatic conditions were also different - here it could be of major importance. It is not possible to compile this data. In the case of air tightness, only one case was found, which was added to the Discussion chapter.

The author should refine the abstract and the conclusions.

The abstract has been rebuilt - the content has been shortened, leaving the most important information. the chapter "Conclusions" has been added.

The "Conclusions" chapter is missing.

As a result of this comment and the suggestion of another reviewer, the chapter "Conclusions" has been added. Some of the content from the Discussion chapter has been moved to the new chapter.

Author Response File: Author Response.pdf

Reviewer 2 Report

Straw is rich in resources all over the world. With hollow structure, straw was thought to be good at thermal insulation and warm keeping. It’s a meaningful work of this paper to study about the straw bale building. However, it would be better if the following information could be supplied:

1. About the straw bale building house. The house plan and size of the house space should be supplied. Is the house divided into small rooms further? The size of the house would influence the heat transfer and airtightness performance.

2. About the building wall section. The cross-section of the house and the infill material details should be supplied, such as the thickness and infill weight on unit length of the straw bale, the overlapping thickness between the clay plaster and the straw bale, and so on. A schematic map about the house wall section would be help for readers to understand it.

3. About the measurement position of the U-value (Figure 5). How did you choice the position for the U-value measurement? Is it on the wall which the inside with structural post, or with straw bale? The position would influence the thermal bridge, and also the U-value. The position would influence the thermal bridge, and also the U-value.

Author Response

Thank you very much for your review and valuable comments!

Kind Regards

About the straw bale building house. The house plan and size of the house space should be supplied. Is the house divided into small rooms further? The size of the house would influence the heat transfer and airtightness performance.

In the article I included the plan of the building as well as the cross-section and detail of the wall (Figure 2, 3, 4). I strongly agree that in a small building it is more difficult to ensure high airtightness, especially in such a building when its compactness ratio is low.

About the building wall section. The cross-section of the house and the infill material details should be supplied, such as the thickness and infill weight on unit length of the straw bale, the overlapping thickness between the clay plaster and the straw bale, and so on. A schematic map about the house wall section would be help for readers to understand it.

As above - I have provided additional information. I hope now the vision of the building is complete.

About the measurement position of the U-value (Figure 5). How did you choice the position for the U-value measurement? Is it on the wall which the inside with structural post, or with straw bale? The position would influence the thermal bridge, and also the U-value. The position would influence the thermal bridge, and also the U-value.

The position of the heat-flux sensor visible in Figure 5,6 (now there are figure 8,9) has been selected in the middle between the wooden posts. In this position, the influence of the wooden posts is as low as possible. This information was in original under Figure 6 (now Figure 9).

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper is well-written and structured, and the topic is interesting. I suggest to the author improve the readability of figures 7, 8, and 9 and change the last paragraph's title to "Discussion and conclusions".

Author Response

Thank you very much for your positive review!

I improved the readability of figures 7, 8 and 9. (In this moment there are Figures 10,11 and 12) I inserted new drawings in the article and corrected the captions under the drawings.

In addition, I have prepared a list of changes that includes changes after comments from all reviewers - please see the attachment.

Kind regards

Author Response File: Author Response.pdf

Reviewer 4 Report

In this paper, a case study for potential risks of the building built with straw bale construction technology was investigated. This topic is very interesting and impressive. The viewer think that this paper is scientific, but there are some errors in the process of writing the article. The specific comments are as follows:

1. The conclusion section should be supplied after the discussion section for this study. Also, some definite conclusions may be given based on the discussion and research.

2. In this study, the author believed that the tested heat transfer coefficient of walls made from straw bale construction technology is uncertain. But, how did the author going to deal with this test uncertain? Also, how do we solve the problems of the risks for the building made from straw bale construction technology mentioned in the study?

3. The viewer believes that another building or building wall made from other construction materials should be provided for comparison in this study.

Author Response

Thank you very much for your positive review. I made a lot of changes and corrections. I have prepared a list of changes that includes changes after comments from all reviewers -Please see the attachment.

Kind regards

Theconclusion section should be supplied after the discussion section for this study. Also, some definite conclusions may be given based on the discussion and research.

As suggested, the Conclusions chapter has been added, therefore the Discussions chapter has been rebuilt - some elements have been moved and some have been added, e.g. the last paragraph concerning air tightness tests (previously it was missing).

In this study, the author believed that the tested heat transfer coefficient of walls made from straw bale construction technology is uncertain. But, how did the author going to deal with this test uncertain? Also, how do we solve the problems of the risks for the building made from straw bale construction technology mentioned in the study?

This uncertainty resulted from the observed changes in other measurements, which were burdened with defects that made it impossible to consider them compliant with the standards. For example, the incorrect study is shown in Figure 18. Such a statement also appears in other authors - it is indicated in the Discossion. I admit that as a result of developing a new drawing (based on a review by another reviewer), which is present in Figure 4. b) Detail, I improved the straw thickness. Earlier, I was using old data 45cm thick, but 43cm thick has been built into the building. I recalculated the U-factor for the 43cm thickness. As a result, the tested values U = 0.19 W / m2 are almost identical to the calculated values (currently in article U = 0.184). In this situation, the results are surprisingly favorable.

I described that it is advisable to re-test the U coefficient. I plan such tests at the beginning of 2023.

I wrote about risk reduction in the discussions chapters and in conclusions.

The viewer believes that another building or building wall made from other construction materials should be provided for comparison in this study.

This is a good idea - especially actual studies on different types of walls. I think it's a good idea to use in the future. I would like to examine hempcreate walls.

Author Response File: Author Response.pdf

Reviewer 5 Report

As general comments, he paper is quite clear in his structure, but both the research context frame and the conclusion should be improved. The contextualization of the work in the introduction chapter seems a bit weak, particularly regarding condensation risks and diffusion-open partitions use issues and the role that both could have in the technology overall hygrothermal and durability performance, and should be better framed. Moreover, The paper could discuss further deeply the relationship between those issues and the results obtained during on-field measures, considering that the research presented verify through on-field tests the risk of condensation and the presence of thermal bridges, but then the conclusions of the paper completely rely on reported literature data.

Certain particular aspects in the text seemed unclear or incoherent:

Table 1, at line 68 apparently show no ratio in listing the sequence of data found in literature by the author, which makes it difficult to interpretate. It could be improved also taking into consideration what stated in lines 64-65.

Line 145 - Layers assumed for U-value calculation seem incongruent. Usually structural elements embedded into the wall section, which do not form a continuous layer are not included in a U-value calculation. If chosen otherwise the reason why should be explained in the text. Moreover the choice does not seem coherent with the in-situ measure program, in which the author took care of placing the sensors so to avoid areas of the wall which would have included the timber structure, as described at lines 161-163.

In Figure 9 at line 185, the graph seems to show a 3cm external render, simingly to the internal plaster and to the previous graph. While in the text at line 178, figure 9 is referred to as a graph showing 1 cm thick llime render. Can the author explain please?

Line 192-194 sense seem confusing, considering what already said at lines 177-175. If the author is suggesting to balance the diffusion resistance of internal plaster and external render, it should be more explicitly and directly clarified in the text.

Line 204 - not clear whta does "(depending on locatin)" means here. Can the author explain better?

In Figure 12 at line 253, the color of the measurement periods bands could differ according to the presence/absence of the occupants, for a clearer and immediate reading of the graph and measurements results. Moreover, it is recommended to place the measure period color bands in the backyard, so to avoid temperature and humidity lines color changing, which could be misleading.

Line 336-337: It is not clear what does the phrase "leak in the building" exactly means in this case. Please explain better.

Line 376-378: It is asserted that foundation and window frames are the main thermal bridges, but the photographs below eventually show high dispersion on the north facade through the leaks and in the beams-wall junction areas, as stated also in the photos' captions. No photo support the statement regarding the foundation.

Line446-448: The author should clarify if the walls of the cited buildings show the same layers of the building tested by him and if the technology used were exactly the same or not; so to better support the hypothesis reported below, about condensation

English should be revised; In many cases seems not fluent and sometimes not adequate to the kind of publication. Moreover recurrent expressions have been detected several times in the text, in certain cases even in the same phrase. Particularly:

Line 27 - "Straw bale buildings have been a technology" does make much sense: There are different technolgies making use of straw for building purposes, as also the author underlines in the text; moreover the tense of the verb seems inconsistent.

Line 82 - the meaning of the phrase is quite misleading, could be improved.

Line 88 - usually "properties" are not "performed".

Line 96 - The concept is repeted from line 82 and still is not so clear

Lines 105-108: English to be evised. First phrase from line 105 should be contextualized and singular/plural use also should be checked. Straw bale technology is better in which terms exactly? Line 107: It is not clear, "As a result" of what exactly? the expression do not seems pertinent here.

Line 111 - "at 60 cm intervals": is not common expression in english, could be improved.

Line 271-277: the phrase "The tests were carried out" is repeated several times, which is bothersome and not fluent. Text fluency here should be stronghly improved.

Line 376-377: The sentence need better english, it does make too much sense as it is.

Line 415-416: the repetition of the word "study" should be avoided.

Line 433: "Measurements" should be replaced by "measures"

Line 454: The sentece does not have verb, which makes hard to understand its meaning.

Author Response

Thank you very much for your review. The comments are very accurate. They testify to a very careful analysis of my article. Thank you a lot for your time.

I tried to take into account all comments. I had the biggest problem with these of a general nature. I corrected the text. Thank you very much, it certainly improved the quality of my article.

In addition, comments from other reviewers were taken into account. Below I answer the questions. In addition, I have prepared a list of changes that includes changes after comments from all reviewers (Please see the attachment).

Kind regards

The sequence of items has been changed according to the first column - lowest first.

For the purposes of the article, I added a drawing showing a fragment of a wall with wooden elements (Figure 4. B) Detail.

On this occasion, I noticed a dimensioning error - the straw bale that was used is 43cm wide, not 45cm as before. (During construction, the spacing of the wooden posts was narrowed so that the bale protruded slightly and could be trimmed and evened out.)

In such a situation, the computational U coefficient turned out to be a bit different, U = 0.18 W / m2K.

During the calculations, the heterogeneity of the wall was taken into account - it was divided into a 58 cm wide (straw) and 4.5 cm wide part (posts 15cm - wood wool 20cm - posts 8 cm).

I checked - computationally the presence of post does not significantly affect the U-value - the difference is 0.001 W / m2K. This is due to the fact that a better insulator was used in this place - wood wool (between posts).

It is certainly a quite specific case. This is confirmed by thermal imaging tests, in which the occurrence of typical thermal bridges was not noticed, but only air leaks through cracks and holes.

For this reason, I think the influence of these elements may be negligible.

Certainly, measurements at the construction site are not an ideal solution for heterogeneous walls, but in order to avoid the influence of the thermal bridge from the wood, the sensor was placed between the wooden posts. Information under Figure 9 (formerly Figure 6).

In the article, I also emphasized that in-situ research can give a high uncertainty of results (this is included in the discussions). I think it would be a good idea to add some more information about the heterogeneity of the wall. Such items will also be added to the part discussion.

That's right, another illustration was included by mistake. To improve this and the overall readability of these illustrations, new ones have been included. The current numbering is Figure 10, 11 and 12. The conclusions are the same and remain unchanged.

Therefore, I propose a change - the walls should be designed in such a way that the materials with the highest diffusion resistance are closest to the interior, and the last outer layers have the lowest possible diffusion resistance (lower than the inner layer).

Line 204 - not clear whta does "(depending on locatin)" means here. Can the author explain better?

Due to the load on the server with a large amount of data, I decided that in places where changes occur less dynamically, measurements will be performed less frequently every 10 minutes (this is the case in walls and at the level of foundations), while measurements, e.g. of external and internal temperature, are carried out more often every 5 minutes . I will add an explanation.

Figure 12 (now 15) has been revised as indicated.

Line 336-337: It is not clear what does the phrase "leak in the building" exactly means in this case. Please explain better.

It has been corrected.

In my opinion, these are not leaks (it's the windward side), but rather a kind of shade. Please pay attention to the black membrane just covered by the walls from rain - here you can also see a delicate light border. It can't be a leak. A similar white border is on the black plastic tube. In these places, under the wooden vertical battens, there is also a black membrane (pos. 9) - as a sealing element. Please see the sketch Figure4b (pos. 9). I added a thermal image of the foundations to the article.

It has been updated.

It has been corrected.

Line 82 - the meaning of the phrase is quite misleading, could be improved.

It has been corrected.

Line 88 - usually "properties" are not "performed".

The noun being "performed" is "tests" not "properties".

It has been corrected.

Line 111 - "at 60 cm intervals": is not common expression in english, could be improved.

It has been corrected.

Line 271-277: the phrase "The tests were carried out" is repeated several times, which is bothersome and not fluent. Text fluency here should be stronghly improved.

It has been corrected.

Line 376-377: The sentence need better english, it does make too much sense as it is.

Corrected, the author's intention was: Thanks to this survey, it was confirmed that there were no typical thermal bridges inside the wall, and these were only mainly leaks and discontinuities in the external plaster.

Line 415-416: the repetition of the word "study" should be avoided.

It has been corrected.

Line 433: "Measurements" should be replaced by "measures"

The sentence has been deleted in the new version of the Discussions chapter.

Line 454: The sentece does not have verb, which makes hard to understand its meaning.

It has been corrected.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The answers are not convincing (1, 2).

1. What is the novelty of the paper?

2. What is the added value of the paper?

6. In the section "Results", are presented the Figures (18, 18, 19, 20, and 21), that do not belong to the author.

Figure 18. Thermal imaging photo of the south side of the building - a section of the wall under the roof eaves. No visible thermal bridges. Source: thermal imaging inspection report [33].

“The indicated photos - I have given the source for this, where the author is also located. I own the copyrights. The author has been added.”

I understand your point of view. The figures have nothing to look for in the "Results" section, as long as they do not belong to you.

7. The author should refine the “Discussion” chapther.

“The chapter discussion has been shortened. Part of the text has been moved to the new chapter Conclusions.”

The author answered superficially.

8. All the data presented in the "Results" chapter must be analyzed in the "Discussions" section.

Specify the lines in the paper.

9. The experimental results obtained must be compared with the results presented in the literature (in tabular for).

The author answered superficially.

Comments for author File: Comments.doc

Author Response

Thank you for your comments. My answers are in italics.

The answers are not convincing (1, 2).

What is the novelty of the paper?

What is the added value of the paper?

I have added an explanation in lines 106 - 112 together with the paragraph 113-117 explaining why this research adds value and is something different from previous research.

In the section "Results", are presented the Figures (18, 18, 19, 20, and 21), that do not belong to the author.

(…)

I understand your point of view. The figures have nothing to look for in the "Results" section, as long as they do not belong to you.

After re-examining the comments from this point, I decided to remove the photos. Currently, this section is very abbreviated in Chapter 2. Materials and Methods - 334-336.

The author should refine the “Discussion” chapther.

“The chapter discussion has been shortened. Part of the text has been moved to the new chapter Conclusions.”

The author answered superficially.

The elements that appeared in the Discussion chapter are marked in yellow. Please indicate your expectations, if they have not been met.

All the data presented in the "Results" chapter must be analyzed in the "Discussions" section.

Specify the lines in the paper.

It was about the elements that in the present article (rev2) are in position 514-526 - these are the elements related to airtightness, which in the first part of the text were not here (and it was in Results).

An excerpt concerning the u-factor measurements and the possible influence of the thermal bridge has also been added 474-480.

All these elements are marked in yellow.

The experimental results obtained must be compared with the results presented in the literature (in tabular for).

The author answered superficially.

Despite my earlier concerns, I included the estimated thermal conductivity coefficient based on this research in Table 1 (The last position in the table). The remaining parameters, as described earlier, I am not able to compare with other values. If this is not enough, I am asking for tips, because I do not know what your expectations are.

All additional changes have been made in Track Changes mode - to make them more visible.

Thank you very much for your time.

Author Response File: Author Response.pdf

Reviewer 4 Report

The author have addressed my comments.

Author Response

Thank you very much for your review and valuable tips!

Round 3

Reviewer 1 Report

1. What is the novelty of the paper?

2. What is the added value of the paper?

“I have added an explanation in lines 106 - 112 together with the paragraph 113-117 explaining why this research adds value and is something different from previous research.”

The mentioned lines do not refer to the novelty and added value of the manuscript.

The answers are not convincing (1, 2).

9. The experimental results obtained must be compared with the results presented in the literature (in tabular for).

The author answered superficially.

Your results must be compared with similar results presented in the specialized literature.

Comments for author File: Comments.pdf

Author Response

I thank you very much for your critical comments. Below are my responses to the reviewer's comments.

What is the novelty of the paper? 2. What is the added value of the paper? “I have added an explanation in lines 106 - 112 together with the paragraph 113-117 explaining why this research adds value and is something different from previous research.” The mentioned lines do not refer to the novelty and added value of the manuscript. The answers are not convincing (1, 2).

The article contains elements indicating that: - variability of straw parameters, - the quality of the building, the method of plastering, - finishing of external walls (protection against rain) - way of living by the inhabitants - climatic parameters All this means that each straw-bale building can achieve different parameters, e.g. thermal, humidity. There is little research into existing buildings, especially in the cold climate of the northern hemisphere. Tests that were made in a slightly different climate and, for example, without external cladding in the form of boarding. Finally, the methods of measuring theses differ slightly between individual authors, as well as the final interpretations of the results. For these reasons, I believe that the article has aspects of novelty and added value to this type of research. Added elements in discussion and conclusions that indicate this.

The experimental results obtained must be compared with the results presented in the literature (in tabular for). The author answered superficially. Your results must be compared with similar results presented in the specialized literature.

I did the comparison requested by the reviewer. The list is presented in table 6. If I have not met the reviewer's expectations, please explain in detail what the problem is. All new items are marked in yellow.

Kind regards MP