Analysis of Long-Term Change in the Thermal Resistance of Extruded Insulation Materials through Accelerated Tests

Round 1

Reviewer 1 Report

1) Page 1, Line 2: In addition to thermal resistance, there are several other thermal properties of materials. So, I suggest changing the title to “… in the Thermal Resistance of …”.

2) P1, L32: Include “thermal resistance degradation by ageing” in the keywords.

3) P2, L74: Give the reference from where equation (2) was taken.

4) Elsewhere. Replace "ISO 11561" by "ISO 11561 [5]".

5) P3, L100-114: This text is so confusing that it is not possible to know which knife was selected to perform the XPS samples. Clarify.

6) P3, L117-121: It is necessary to perform a detailed presentation of the parameters measured, of the devices used for that and of the resolution and the accuracy of these equipment’s.

7) P3, L121: References [10, 11, 12] are "discarded" into the text, without any background.

8) P4&P7, Figures 2 & 4: Figures 2 and 4 are not referred to in the text. These figures must be mentioned to in the text and clarification must be given as to what they represent and what are their contribution to the study.

9) P4, L132-137: The description of test methods A and B of ISO 11561 is unclear. Please revise their description.

10) Equations (3) to (13): Equations (3) to (13) were taken from bibliography. Then, the corresponding references must be cited.

11) P4, L146: Not "r". Uniformize the designation of variables.

12) P4, L153: Replace “… after time t and …” by “... in day t and …”. To be coherent, the time is in days.

13) P5, L166-168: Define the meaning of variables appearing in equations (8) and (9).

14) P5, L178-183: What characteristics are represented by "d" “d0”, “D” and "D0"?

15) P5-6, Equations (11), (12) and (13): Equations (11), (12) and (13) are not compatible with equations (1), (14) and (15). There is an error in these equations. I think it is in equations (12) and (13), because according to equations (1) (14) and (15) equation (13) must be S = d^2 / d0^2. The error can also be in equation (11) and in this case this equation would be t0 = t . S.

16) P6, L205-208 and elsewhere: In addition to ageing, the thermal resistance also depends on the material in question and the thickness considered. Therefore, whenever it is indicated (or graphically represented) the material in question and the thickness considered must be specified.

17) P7, Figure 4: Identify the Korean standard cited in Figure 4?

18) P7, Figure 4 caption: The acronym of “expanded polystyrene” is EPS and of “extruded polystyrene” is XPS. Then, Figures 4 to 9 shown the thermal resistance of XPS or of EPS?

19) Figures 4 to 9. Degrees Kelvin must be represented by the capital letter "K".

20) Figures 4 to 9. The identification with a mark of the "transition point" in each curve will be enlightening.

21) P7, before Figure 4: Explain in the text body the meaning of: "Special grade (1st floor)", "Special grade (2nd floor)", "Special grade #1" and "Special grade #2".

22) P7, L217-219: It is necessary to provide a justification for the difference between the values presented in Figures 5, 6 and 7 for the thermal resistance of the two samples.

23) P7, Figure 5: Both in the text and in the other figures, time is indicated in hours. Therefore, it is recommended that this also happen in Figure 5.

24) P8, Figure 7 caption: The number of the equation used to calculate the relative thermal resistance of the two samples must be given here.

25) P8, L231-235: The values shown in Figure 7 are for "relative thermal resistance", therefore they are dimensionless values. So, contrary to what is written, the (dimensional) values indicated for the thermal resistance were not directly taken from Figure 7. Elucidate how they are obtained.

26) P9, Table 1: Table 1 is not referred in the text. It must be mentioned in the text and clarification must be given about what it represents and what is its contribution to the study under consideration. In addition, the material in question, its thickness, what the terms "specimen A" and "specimen B" represent and what distinguishes them must be indicated.

27) P9, L249: “From equation (14), it can ...”.

28) Figures 8 and 9: What is the meaning of "sample 1" and of "sample 2" and what are their relationship with "1st floor" and "2nd floor"?

29) Figures 8 and 9: As they are not measured, from what reference(s) were taken the results for the "actual long-term tests"?

30) Figures 8 and 9: "actual long-trem test" is meaningless. Eventually "actual long-term test".

31) Figures 8 and 9: "accelerated labortory test" is meaningless. Probable "accelerated laboratory test".

32) P10, L278-279: “... suggested by ISO 11561 [5] using a 10 mm thickness sample of XPS ...”.

33) P11, L306, L307, L323-324, L327, L328: References 1, 2, 10, 12 and 13 are incomplete.

Author Response

Please see the attachment(2 File).

Author Response File: Author Response.docx

Reviewer 2 Report

The article presents an important issue which is the deterioration of thermal properties of insulating materials with time. The results of tests carried out after the actual elapse of time and the accelerated method approved by the Standard were compared. However, I have a few comments that should be considered before proceeding with the manuscript:

Introduction:

• Line 41: “Insulation materials used in buildings are classified as inorganic and organic insulation materials”. It would be useful to give examples of such isolations in parentheses.
• Line 46: “Extruded insulation materials are made by foaming gas, with a lower thermal conductivity than air”. It would be useful to provide a range of thermal conductivity values and a reference to the literature.
• Line 48: “However, this foaming gas is gradually released over time and replaced with external air, which degrades the insulation performance of the materials”. By how many percent can the lambda value increase after the gas is released and replaced with air? It would be worth writing it down.

2.1 Specimen and measurement conditions

• It would be worth giving the exact name (brand) and manufacturer of the insulation material under test. Perhaps the manufacturer's data is available on the lambda value of their product.
• It should be written how many samples from a given type of thermal insulation were tested in one time period. Was the result averaged somehow or was there one measurement?

Discussion:

• The discussion of the results is poor. It is limited to reading the results from the graph. Is it possible to supplement the discussion with comments on the results obtained? Maybe some comparison with other studies, because the bibliography is also poor for a scientific article in the MDPI publishing house.

Other:

• No reference in the text to Figures 2 and 4.
• Line 206 and others (graphs) - the unit of thermal resistance should be written like this: (m²∙K)/W. Remember the order of the math operations.
• Figure 4: Mark what thickness of the sample the results apply to. Although it is written earlier, it should also be written here for the sake of clarity.
• Figure 1 b): Linguistic mistake. Specimen, not speciment.
• Line 117: “Heat Flow Meters HFM 436 Lambada Series”. Lambda, not Lambada.
• Figure 8: “accelerated labortory test”. Did you mean “laboratory”? 
• Please re-edit the manuscript for mistakes such as those mentioned above.
• Line 282: “…compared to the initial value of the 50 mm specimen analysed in the previous study”. The reference to the publication should be provided.

Author Response

Please see the attachment.(2 File)

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

I have no remarks to post.

Reviewer 2 Report

Thank you for responding to my comments. The quality of the article has been improved.