Historic Building Energy Audit and Retrofit Simulation with Hemp-Lime Plaster—A Case Study

Round 1

Reviewer 1 Report

The paper presents a study on the use of hemp-lime composite in the construction sector. The study fails to clearly describe the methodology and mathematical models/simulation tools used to develop the case study. Furthermore, the paper does not present any validation of the models used. A comparison with other thermal insulation materials would be important to be included in the article, instead of only analysing the use of this specific thermal insulation material. Some of the details and figures provided in the article (e.g. photos of the interior of the building) are irrelevant and should be removed if the article is to be published. The conclusion section is wordy and only address the actual results obtained in the study in the second half of the section.

Author Response

The authors wish to thank the Reviewer for his comments and suggestions, which have allowed the authors to improve the quality of the manuscript. We improved the description of the methodology and and mathematical models/simulation tools used. The hemp lime has not been validated with other materials but in the introduction section some references to a recent European project that tests other materials, have been added, and the choose of the hemp lime was motivated. As requested the Fig. 1 has been deleted.

Reviewer 2 Report

The subject of the use of natural insulation materials for the retrofit of historic buildings is an interesting one and one that merits more investigation. As such the article has merit. However, the thermal transmittance and thermal resistance calculations are erroneous. This calls into question the validity of all the results.

Further justification is required as to the choice of methodology. Why use a case study? Why use the chosen software? Why use steady state interstitial hygrothermal and mould prediction calculations and not dynamic modelling?

The article would also benefit from a comparison of the hemp-lime plaster/render with a more conventional insulation material, with regards to cost, environmental impact, thermal performance, buildability etc.

There are also numerous linguistic problems that must be resolved.

Please see the attached mark-up for detailed comments.

Comments for author File: Comments.pdf

Author Response

We checked the thermal characteristics in Table 3 (namely U and R): in the study they are not calculated by the authors but by the software for each wall (different thickness) by using input characteristics. The values reported in the paper were actually wrong, because they were calculated manually for a thickness of 10 cm, though the Table caption says 10 mm. We thank the reviewer for catching this error, and we decided to remove those 2 columns since those are not the actual values used for the simulation. 

Reviewer 3 Report

It's definitely a case study article. However it's quite well written and interesting.

The results can be interesting for the other reaserchers which examin the similar scientific problems.

The quality Fig. 2 and 3 should be improved.

Author Response

The authors wish to thank the Reviewer for his comments and suggestions, which have allowed the authors to improve the quality of the manuscript. As requested the Fig. 2 and 3 have been improved.

Round 2

Reviewer 1 Report

The authors have introduced improvements to the manuscript, including more references and a more detailed background in the Introduction as well as an extended description of the methodolgy and models applied. The English is good and the analysis present a structured summary of the results obtained in regard to the case study.

In order to be able to place the results in an overall context, the authors are required to extend their analysis by including other thermal insulations materials such as XPS, EPS, VIP, PUR/PIR, etc. This will allow the reader to assess the true benefit of the use of hemp-lime plaster as compared to other conventional and state-of-the-art thermal insulation materials. The Conclusion Section is too wordy; it should be a concise summary of the main findings without repeating the motivitation at the begining of this sections. Moreover, the conclusions need to include quantitative results in order to be able to assess the benefit of the studied material. The authors are required to address these points in detail and provide a detailed response. 

Author Response

We are very happy that the reviewer noticed an improvement in the manuscript and we tried to work on the reviewer suggestions.

Unfortunately, for the authors it is impossible to carry out more simulations to include a numerical comparison of more materials. This is a huge task that cannot be carried out in just 5 days and, although very interesting, is beyond the scope of this paper.

We included some literature studies about other insulation materials in the introduction; we hope it can increase the quality of the manuscript and satisfy the reviewer.

The Conclusions section has been simplified in the first part and additional quantitative details have been provided.

Reviewer 2 Report

Many of my comments have been addressed, however the following still remain.

The caption for table 3 should be corrected (line 212 & 213) deleting "Characteristics marked with * refer to a 10 mm thickness layer". This is no longer required following amendments already completed by the authors.

Figure 3 is a table and as such should be labelled "Table 4" with the caption above the table. Subsequent figures and tables will require renumbering.

Figure 4 is again a table and should be labelled as such, as is figure 5.

The previous comment on figure 6 (now figure 5) has not been addressed. "Over half of these walls are partitions. Why are U and Y values important for these walls? One would expect them to be adiabatic unless the rooms on either side have very different heating regimes."

The limitations of steady state calculations using EN ISO 13788/2012 should be outlined, as previously noted. 

Author Response

We thank the reviewer for his generous overall evaluation. In the following a point by point answer to the raised questions:

- Tab. 3 still includes surface mass density which is calculated for a 10mm thickness layer. This is why that sentence is still there.

- Fig. 3 and Fig, 4 have been turned into Table and all other figures and tables have been renamed. Sorry for forgetting it in the first resubmission.

- The reviewer is right, however in South Italy is very common, especially for ancient building, that adjacent rooms are heated up differently, for example because one room is used and the other one is not. This is why we did not considered the partitions adiabatic and the U and Y values make sense.

- Lines 255-258 have been added to outline that the use of different models may lead to different results. We would like to note that the aim of this study is not the evaluation of the absolute thermal performance of hemp-lime (in which case different tests and models would have been used) but only the assessment of possible benefits in terms of thermal performance increase deriving from the use of hemp-lime plaster compared to standard one.

Round 3

Reviewer 1 Report

Although the authors have not included an extended analysis comparing with other thermal insulation materials, it is understandable that such a extension is beyond the scope of this work. In this regard, the authors have strived to expand their literature review, which (partially) compensates for the lack of a more extensive comparison in this study.