Thermo-Energy Performance of Lightweight Steel Framed Constructions: A Case Study
Round 1
Reviewer 1 Report
Dear authors,
thank you for submitting the revised manuscript. The manuscript has clearly been improved. In the following you find a few comments of issues that I would advise to address before publication:
- In equation (3) the length l should also have the index j or j should appear on the left hand side of the equation. In the same equation it is inconsistent that the upper limit of the summation contains the index j that is summed over.
- In equation (4) the indices i and j appear on the right hand side of the equation without summation but they do not appear on the left hand side.
- In the third paragraph of the conclusions you write that "the choice in thermal insulation material must be redirected towards nano-insulation materials." It does not become clear to me how you come to this conclusion. Such materials have not been mentioned before in the paper and you do not provide any explanation what properties they have (except for being thinner) that make them advantageous.
Author Response
The authors would like to express their sincere gratitude to the reviewer for the careful and thorough reading of the paper and for the thoughtful and useful comments, and wise constructive improvement suggestions, which have helped to improve the quality of the manuscript. The authors took into consideration the suggestions of the reviewer, and some work was carried out to improve the paper as recommended.
“In equation (3) the length l should also have the index j or j should appear on the left-hand side of the equation. In the same equation, it is inconsistent that the upper limit of the summation contains the index j that is summed over.”
Answer: Sorry, it was a typo error: now the length l also has the index j. Regarding the inconsistency of the upper limit of the summation, we agree with the reviewer, but this is how it is written in standard ISO 10211 (Equation (18)). Nevertheless, we remove the index as suggested by the reviewer.
“In equation (4) the indices i and j appear on the right hand side of the equation without summation but they do not appear on the left hand side.”
Answer: Sorry, it was a typo error. Anyhow, we verified the formula and adjusted it according to the case scenario described by our models, respectively the case of two boundary temperatures.
“In the third paragraph of the conclusions, you write that "the choice in thermal insulation material must be redirected towards nano-insulation materials." It does not become clear to me how you come to this conclusion. Such materials have not been mentioned before in the paper and you do not provide any explanation what properties they have (except for being thinner) that make them advantageous.”
Answer: Notice that in the original submitted version, in page 16 (now page 17) (paragraph before Eq. (15)), are mentioned the super insulation materials, such as vacuum insulation panels and aerogel insulation, as well as three references [42-44] (now [45-47]). Nevertheless, as suggested, more details and specifications are mentioned in the text. These nano-insulation materials, also designated as super insulation materials (SIM), have very reduced thermal conductivities (around 15 mW/(m·K) or even lower). Since Reviewer 2, suggested to complete the literature review in the Introduction section, this could be one of the topics addressed.
Reviewer 2 Report
The paper presents the thermo-energy performance of steel-framed constructions. A case study. It is supported by 45 references. Comments are listed below:
- Literature review should address more on research questions rather than simply a summary of past studies
- The aims and objectives should be stated explicitly based on the research questions identified from literature review.
- There is a lack of experimental results to validate the simulation results
- Discuss the impacts of the U-value results on the cooling or heating demand in the experimental house.
- Comparisons of the thermal performance should be made with the conventional envelope design.
- Discuss how the proposed design can be adapted to different climatic regions. How the cooling or heating energy can be minimized?
- Conclusions should highlight the novelty and limitations of the study.
- Explain how the PV panels can sustain electrical usage to facilitate net zero carbon emissions.
Author Response
The authors would like to express their sincere gratitude to the reviewer for the careful and thorough reading of the paper and for the thoughtful and useful comments, and wise constructive improvement suggestions, which have helped to improve the quality of the manuscript. The authors took into consideration the suggestions of the reviewer, and some work was carried out to improve the paper as recommended.
“Literature review should address more on research questions rather than simply a summary of past studies”
Answer: As suggested, the literature review in the Introduction section was updated and completed.
“The aims and objectives should be stated explicitly based on the research questions identified from the literature review.”
Answer: As suggested, the aims and objectives of this research work are now explicitly stated.
“There is a lack of experimental results to validate the simulation results”
Answer: Yes, we agree with the reviewer, but the main focus of this research work is not on the experimental measurements (which will be performed in the near future), but in the simulations and computations which were performed in the design stage, as well as in the parametric study. We started two weeks ago the real monitoring of the house for one year, implementing a scenario in which the house is in the operational stage, thus validation of the modelled simulation results will be made available.
“Discuss the impacts of the U-value results on the cooling or heating demand in the experimental house.”
Answer: The impacts of the -values on the heating demand of the experimental house were already indirectly discussed in Figure 11, where it can be identified the envelope components with higher heat losses and, therefore, their performance could be improved by decreasing their thermal transmittance values. Nevertheless, we included a new sub-chapter (i.e. 4.5) where a parametrisation was done for the U-values to assess the impact on the heating demand. Considering that Romania is a cold dominated country defined by large heating periods for the buildings, we highlighted only the impact of the thermal design of the building on the heating demand.
“Comparisons of the thermal performance should be made with the conventional envelope design.”
Answer: The Romanian design legislation requires a design report that shows the fulfilment of the code prescriptions in terms of the minimum recommended thermal resistances design values. This is necessary to obtain de building permit for the new building. Therefore, a comparison of the obtained results must be done against the reference values defined in the national design norms. In this regard, the discussions are provided in the explanations paragraph for figure 10. In order to make an accurate comparison against a conventional envelope design (e.g. masonry), considering that a bi-dimensional study was employed and the thermal performance was established in direct connection to all building junctions, one will need to perform the same steps for a building having the same geometric characteristics but conventional constructive detailing for the building envelope. In this way, the results can be compared. Unfortunately, this was not the aim of this paper, and therefore we only compared the results to the imposed normed values.
“Discuss how the proposed design can be adapted to different climatic regions. How the cooling or heating energy can be minimized?”
Answer: This was one of the main objectives of the parametric study presented in Section 4.4, where it was assessed the influence of the ventilation rate, curtain-wall orientation and heating system efficiency. It was concluded that for colder climate regions the heating energy demand can be minimized by reducing the ventilation rate, orientating the curtain wall to the south direction and selecting a heating system with higher efficiency.
“Conclusions should highlight the novelty and limitations of the study.”
Answer: As suggested, now the novelty and limitations of this research work are highlighted in the Conclusions section.
“Explain how the PV panels can sustain electrical usage to facilitate net-zero carbon emissions.”
Answer: It is well known that nearly Zero Energy Buildings (nZEB) should have a very high operational energy efficiency and the remaining reduced energy needed should be provided by renewable energy sources, such as solar energy, including the electricity provided by PV panels. In the experimental house, the PV panels are placed for both, complementing the electrical usage to facilitate net-zero carbon emissions, but also to make the house independent – no other energy sources. Authors are aware of the increased embodied energy when the thickness of the thermal insulation is augmented (to reduce -values and increase energy efficiency), as well as the one existing in PV panels (used to increase energy supply from renewables). This is now explicitly mentioned in the text.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
The paper investigates the thermo-energy performance of steel-framed constructions. It is supported by 46 references. The case study forms a basis to deliver comprehensive results on the advantage of the construction. To enhance the archival value of the paper, some limitations and considerations of applying the construction should be discussed briefly in terms of the building height restriction, climate conditions, life cycle cost, rigidity against natural disasters, etc. The active HVAC, lighting systems, etc. and other renewable applications that can complement the constructions may be highlighted.
Author Response
The authors would like to thank the reviewer for the thorough review of our manuscript and the valuable and helpful comments. We have carefully reviewed the comments and have revised the manuscript accordingly. Our responses are given in a point-by-point style. Changes to the manuscript are shown in green highlight in response to the reviewer’s comments. We hope that the revised version is now suitable for publication and look forward to hearing from you.
Thank you for the comments. We highlighted in chapter 2 several aspects regarding the mentioned criteria. In this paper, we aimed to present the comprehensive modelling and simulation research for the LSF module, which was not previously discussed. More information on the active solutions, mainly renewables, will be provided in a following paper, after the second monitoring phase will be finalized.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This paper deals with the calculation of energy performance of a lightweight steel-framed construction. The thermal performance is calculated in terms of adjusted thermal resistances and global thermal insulation coefficient. Then, the heating consumption is estimated and associated to the respective energy rating in compliance with the Romanian regulations.
In the reviewer's opinion, unfortunately this paper does not meet the minimum requirement for publication, being a trivial application of well-known methodologies (ISO 6946, EN ISO 10211) to a single case study.
Indeed, neither the methodology employed for the calculation nor the analysis of the results present the scientific soundness required for the publication on international, scientific journal on building science such as Buildings.
For the above mentioned reasons, the recommendation of the present reviewer is to reject the paper.
Author Response
The authors would like to thank the reviewer for the thorough review of our manuscript and the valuable and helpful comments. We have carefully reviewed the comments and have revised the manuscript accordingly. Our responses are given in a point-by-point style. Changes to the manuscript are shown in green highlight in response to reviewer’s comments. We hope that the revised version is now suitable for publication and look forward to hearing from you.
We appreciate your comment. The paper is part of one of the research activities conducted during the development of the project mentioned in the acknowledgments part. This paper aimed to offer an image of the experimental module in terms of thermal and energy performance, and at the same time, indicate to what extent it is compliant with the Romanian nZEB regulations. Therefore, the study was focused just on the designed and executed prototype and not on the presentation of various case scenarios. A future paper will question, through a parametric study, to what extent the building envelope can be optimised in order to reach the desired nZEB values for all climatic zones from Romania.
Regarding the presented study of the joints defining the building envelope, the study was not a trivial one, considering the complexity that describes the metallic structures, more accurately, the constructive details of steel structures. In order for the results to be valid, advanced knowledge of modelling and design as well as dedicated software must be employed. At the same time, it gives an image of the future steps in continuing the project.
Author Response File: Author Response.docx
Reviewer 3 Report
The authors present a thermal simulation study of the building envelope for a small Light Steel Frame building. It appears to be a solid peace of work but I strongly recommend some revisions before publication. I recommend to the authors to extend the introduction and conclusion in a way that helps the reader to understand better why their work is of interest for the community and how their findings can be useful in other contexts than their case study.
My other comments refer to the presentation of the methodology and the results:
- The authors provide an extensive description of the layout and construction details of their case study object in the text. Here, some space could be saved by referring to the drawings.
- The authors describe a measurement setup with sensors in the building and the building envelope. However, the presented results come only from simulations. Using measurement results to validate the simulation results would significantly improve the manuscript. If measurement results are not used it is unclear why the sensor setup is described in such detail.
- Several quantities are unsufficiently defined or motivated. This includes L^{2D} (thermal coupling between what components/media?), R' (how does it differ from R and R_{tot}?), and f_{Rsi} (why is this an important quantity?). Please define the quantities in a way that readars who are not every-day users of your software and the underlying standards can understand them.
- In line 307 a reference number is missing.
- In figure 19 values on the x axis and units are missing.
Author Response
Thank you for the comment. We added some more information and ideas to the conclusions part.
Comment 1: The authors provide an extensive description of the layout and construction details of their case study object in the text. Here, some space could be saved by referring to the drawings.
Response: Thank you for the comment. Considering that the paper presents one case study, we tried to describe the investigated case properly. That is why we included visual and textual descriptions. Nevertheless, we have rearranged the text and some figures to save some space.
Comment 2: The authors describe a measurement setup with sensors in the building and the building envelope. However, the presented results come only from simulations. Using measurement results to validate the simulation results would significantly improve the manuscript. If measurement results are not used it is unclear why the sensor setup is described in such detail.
Response: Thank you for the comments. We have taken out the picture and adjusted the text in order to send the reader looking for more information on the monitoring data to the referred paper. The aim was to present some of the development stages by including a short description of the monitoring system. Nevertheless, the measurements to validate the simulations are the objective of a subsequent paper, considering that the second monitoring phase is underway.
Comment 3: Several quantities are unsufficiently defined or motivated. This includes L^{2D} (thermal coupling between what components/media?), R' (how does it differ from R and R_{tot}?), and f_{Rsi} (why is this an important quantity?). Please define the quantities in a way that readars who are not every-day users of your software and the underlying standards can understand them.
Response: Thank you for the comment. We have added more information and rearranged the text so that the reader is able to understand their significance and the difference between them.
Comment 4: In line 307 a reference number is missing.
Response: Thank you for the comment. We have added the reference at the indicated line.
Comment 5: In figure 19 values on the x axis and units are missing.
Response: Thank you for the comment. We have readjusted the representation according to your comment. For the x-axis, we refer to the three sets of R’ values. Thus, the corresponding value and its unit measure is found on y-axis.
Round 2
Reviewer 2 Report
The paper has been revised, nevertheless in my humble opinion, the main problem of this paper is represented by the scientific soundness. Indeed, the introduction section is weak, as it just describes the very well-known framework about energy consumption in Europe and the respective regulatory context. Speaking specifically about the contents, the paper looks like a detailed technical report of a case study. In this reviewer's opinion, authors should highlight the novelty of the results and how these contribute to the scientific literature by bringing additional knowledge. Otherwise, this article would represent a mere application of well established methodologies to a case study.
