Historical Analysis of Real Energy Consumption and Indoor Conditions in Single-Family Passive Building

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article addresses the subject of passive houses and aligns with the current trend of promoting energy and environmental sustainability. In this study, the authors present findings from their measurements of indoor air temperature and energy consumption required to maintain it.

The topic is of significant interest, and the measurement results merit further discussion. However, improvements are needed in the presentation of test results, methodology description, and error analysis. Despite a logical chapter structure, the article conflates the methodology, research facility description, and results. The purpose of using simulations for heating or hot water selection is unclear, especially given that the article does not aim to compare energy consumption across different systems.

The method of evaluating thermal conditions and categorizing rooms based solely on ambient temperature, rather than full thermal comfort, is oversimplified and should be noted in the limitations section.

There is a discrepancy between the air temperature graphs and the defined heating and cooling periods, which would benefit from more detailed explanations and descriptions in the text. Additionally, it is unclear whether the values refer to individual measurements or averages. If they are averages, the specific type should be clarified.

Table 16 includes all energy sources, but the methodological basis for determining the inputs is not sufficiently explained in the initial section. For instance, which ventilation system is used, and does it operate on a predetermined schedule?

The article presents research results on energy demand and references standard values. However, it is unclear how the use of a fireplace and direct combustion should be interpreted regarding air cleanliness and CO₂ emissions reduction. It would be beneficial to clarify whether this solution aligns with passive house principles.

The figures are incorrectly numbered. Additionally, a section on the limitations of the method and measurements is missing.

 

Author Response

Dear Reviewer

Thank you very much for the comments. They were absolutely justified. Taking them into account made it possible to enrich the article and raise its scientific level. All changes were made in track changes mode.

Regards

Authors

 

The following changes were made in respond to the comments.

1. The purpose of using simulations for heating or hot water selection is unclear, especially given that the article does not aim to compare energy consumption across different systems.

This issue is further clarified in the section 2.2.3 Building’s Technical Systems and further highlighted in the summary.

2. The method of evaluating thermal conditions and categorizing rooms based solely on ambient temperature, rather than full thermal comfort, is oversimplified and should be noted in the limitations section.

We fully agree with the comment. An additional section 2.4 Limitations of the methodology and measurements, has been included in the article

3. There is a discrepancy between the air temperature graphs and the defined heating and cooling periods, which would benefit from more detailed explanations and descriptions in the text. Additionally, it is unclear whether the values refer to individual measurements or averages. If they are averages, the specific type should be clarified.

This issue is explained in the section 2.3 Data processing and methodology for temperature analysis and 3.1 Assessment of Indoor Thermal Comfort. Additionally the precise assessment of two weeks external weather events was expanded and include statistical analysis for all years.

4. Table 16 includes all energy sources, but the methodological basis for determining the inputs is not sufficiently explained in the initial section. For instance, which ventilation system is used, and does it operate on a predetermined schedule?

This issue is further clarified in the section 2.2.3 Building’s Technical Systems and Table 4.

5. The article presents research results on energy demand and references standard values. However, it is unclear how the use of a fireplace and direct combustion should be interpreted regarding air cleanliness and CO₂ emissions reduction. It would be beneficial to clarify whether this solution aligns with passive house principles.

This issue is further clarified in the section 2.2.3 Building’s Technical Systems.

6. The figures are incorrectly numbered.

The numeration of Figures was corrected.

Reviewer 2 Report

Comments and Suggestions for Authors

In the article, the authors undertake an analysis of actual energy consumption and internal conditions in a passive single-family house. They assess five years of data on indoor temperature and thermal comfort according to the EN 16798-1 standard, comparing them with the requirements for passive and nearly zero-energy buildings (NZEB). The article is grounded in the theory of passive building, embraced as a strategy to minimize energy consumption through optimal design and effective energy management. The research design involved analyzing data over a five-year period to estimate thermal comfort levels and energy usage in the examined building. Specifically, the study compares actual energy consumption with theoretical NF15 and WT2021 standards. The study accounts for a variety of factors influencing thermal comfort and energy use. In my opinion, basing the analysis on data from a single building significantly limits the generalizability of findings to other buildings with similar characteristics. Furthermore, the results regarding energy efficiency may vary when applying different systems, a topic that is not addressed in the publication. Consequently, the article does not add substantial value to the discussion on optimal technologies for passive construction. The authors reference NF15 and WT2021 standards but do not present results from other building types or energy standards, making it challenging to assess the true added value of the findings. The lack of a broader context complicates the evaluation of the extent to which a passive building surpasses conventional solutions in terms of energy efficiency and thermal comfort. A comparison of this building's results with other similarly rated buildings, as well as with buildings of lower efficiency, could enrich the study. The authors suggest the installation of a photovoltaic system; however, there is an absence of analysis on the potential energy benefits of this solution. In my opinion, the literature referenced in the article is insufficiently robust. In its current form, the article is not suitable for publication.

Author Response

Dear Reviewer

Thank you very much for the comments. They were absolutely justified. Taking them into account made it possible to enrich the article and raise its scientific level. All changes were made in track changes mode.

Regards

Authors

 

The following changes were made in respond to the comments.

1. In my opinion, basing the analysis on data from a single building significantly limits the generalizability of findings to other buildings with similar characteristics. Furthermore, the results regarding energy efficiency may vary when applying different systems, a topic that is not addressed in the publication. Consequently, the article does not add substantial value to the discussion on optimal technologies for passive construction.

The paper is not aiming to be another theoretical consideration of passive construction, which has already been the subject of numerous articles. Nor is it intended to generalize anything to other buildings. It is an analysis of a specific case and shows the effects of a correct and thoughtful approach to the issue of designing and the process of constructing a passive building. The achieved standard of thermal protection reduces the required power of the heating system to a minimum. What kind of heating system is used in the building is practically of little importance from an user perspective, because it does not affect much the operating costs. However, it has a very large impact on investment costs. The embodied carbon footprint associated with building a system using a heat pump in comparison to direct electric heating, will also be larger. This is one the basic conclusion of the analysis of this case, making a contribution to the issue of passive construction.

It is worth noting that the cost of construction of the building at the date of completion in 2016 was no higher than the cost of constructing a standard building, due primarily to two factors. First of all, thanks to the simple architecture and design. Secondly due to the lack of need for an expensive, traditional heating system. Originally, it was planned to use a ground source heat pump and water floor heating. The cost of such solution accounted for about 17% of the construction cost. Eventually, after considering the energy modelling results and economic analysis, this cost was avoided (electric floor heating was chosen), significantly reducing construction costs.

The aspect of technical system selections is further clarified in the section 2.2.3 Building’s Technical Systems and highlighted in the summary.

In order to extend the technical system analysis a chapter 5. Photovoltaic system was added. It includes the selection of PV system for the building.

2. The authors reference NF15 and WT2021 standards but do not present results from other building types or energy standards, making it challenging to assess the true added value of the findings. The lack of a broader context complicates the evaluation of the extent to which a passive building surpasses conventional solutions in terms of energy efficiency and thermal comfort. A comparison of this building's results with other similarly rated buildings, as well as with buildings of lower efficiency, could enrich the study.

We fully agree with the comment. An additional information about different energy standard was included in section 1.1 Energy standards.

3. The authors suggest the installation of a photovoltaic system; however, there is an absence of analysis on the potential energy benefits of this solution.

This issue is explained in additional chapter 5. Photovoltaic system. It includes the selection of PV system for the building.

4. In my opinion, the literature referenced in the article is insufficiently robust.

Additional literature studies were conducted and 8 additional sources were cited in the article.

Reviewer 3 Report

Comments and Suggestions for Authors

Comments

 

The paper “Historical Analysis of Real Energy Consumption and Indoor Conditions in Single Family Passive Building” examines a five-year performance analysis (2018-2022) of a single-family passive house near Warsaw, Poland. The study evaluates real energy use and indoor comfort, adhering to current standards, with additional assessments during extreme weather periods. Findings indicate that the building maintains consistent thermal comfort and energy efficiency, even without active cooling, aligning closely with passive house and nearly zero-energy standards. The authors also suggest that adding photovoltaic (PV) systems could enhance energy self-sufficiency, supporting sustainability goals in residential construction.

 

This paper provides a well-structured and thorough investigation into the long-term energy performance and indoor comfort of a passive house in Poland. The authors effectively combine empirical data with standard-based assessments, resulting in a detailed evaluation of passive building benefits under real-life conditions. The study is particularly valuable for its focus on both typical and extreme weather scenarios, which adds depth to the analysis of passive design efficacy.

To enhance the quality and impact of this paper, I would suggest the following improvements:

 

1.     While the study covers a wide range of data, providing additional detail on the data collection process, such as sensor placement and accuracy, would strengthen the robustness of the results and allow for better reproducibility.

2.     The paper mentions that energy use in passive buildings often varies with occupant behavior. Including a more comprehensive analysis or a survey of occupant habits (e.g., frequency of window opening, use of heating and cooling systems) could provide insights into the variations in energy performance observed and clarify the role of user behavior in passive house efficiency.

3.     The potential for PV integration is mentioned, but a more detailed analysis (e.g., potential energy savings, cost-benefit analysis, feasibility of installation) could provide a practical outlook on achieving net-zero or positive energy status, making the study more applicable for readers interested in PV solutions.

4.     Adding graphical representations for year-over-year comparisons, such as heat maps or trend lines of indoor temperatures and energy consumption, could make the findings more accessible and visually engaging for readers.

5.     The findings in the paper are presented clearly and descriptively, providing a solid overview of the observed comfort levels and energy consumption patterns. To further strengthen the robustness of these findings, however, it may be beneficial to incorporate additional statistical validation. Including statistical tests or calculating error margins for key results could enhance the reliability of the conclusions, helping to confirm that the observed patterns in comfort and energy efficiency are both consistent and statistically significant. This added layer of analysis would likely increase confidence in the study's outcomes, providing readers with a stronger basis for understanding the consistency and impact of passive building performance.

6.     To provide additional context and strengthen the introduction, it might be helpful to include a brief discussion on the broader issue of greenhouse gas (GHG) emissions resulting from the energy sector. Highlighting the environmental impact of GHG emissions, particularly in relation to residential energy consumption, would underscore the importance of sustainable building practices like passive house design. For this purpose, I suggest consulting the following published articles on the topic (please note that these references are purely for guidance and are not mandatory for citation): 

·      Ciancio, V., Salata, F., Falasca, S., Curci, G., Golasi, I., & Wilde, P. (2020). Energy demands of buildings in the framework of climate change: An investigation across Europe. Sustainable Cities and Society. https://doi.org/10.1016/j.scs.2020.102213.

·      E. De Cristo, L. Evangelisti, G. Battista, C. Guattari, R. De Lieto Vollaro, F. Asdrubali, Annual Comparison of the Atmospheric Urban Heat Island in Rome (Italy): An Assessment in Space and Time, Buildings 13 (2023). https://doi.org/10.3390/buildings13112792.

7.     The paper presents valuable insights into the long-term performance of a passive house, particularly through real-world data on energy consumption and thermal comfort. However, the methodological approach, focusing on descriptive analysis of historical data, could be viewed as somewhat conventional within the field of sustainable building research. Passive building performance studies often employ similar monitoring approaches, and many have already established the effectiveness of passive design principles in maintaining comfort and reducing energy consumption. To increase the originality of the work, the authors might consider expanding their approach. For example, integrating more advanced analytical methods would add depth and innovation to the study. Additionally, exploring new variables, such as air quality or humidity levels, or examining user behavior in relation to building performance, could provide unique insights that are less commonly addressed in passive house research. These additions would help distinguish the study within the existing body of literature, offering readers a fresh perspective on passive building efficacy in diverse conditions.

8.     Typos must be checked and corrected.

 

 

 

 

Author Response

Dear Reviewer

Thank you very much for the comments. They were absolutely justified. Taking them into account made it possible to enrich the article and raise its scientific level. All changes were made in track changes mode.

Regards

Authors

 

The following changes were made in respond to the comments.

1. While the study covers a wide range of data, providing additional detail on the data collection process, such as sensor placement and accuracy, would strengthen the robustness of the results and allow for better reproducibility.

This issue is further clarified in the sections 2.2 Collection of energy parameters and weather data and  2.3 Data processing and methodology for temperature analysis

2. The paper mentions that energy use in passive buildings often varies with occupant behavior. Including a more comprehensive analysis or a survey of occupant habits (e.g., frequency of window opening, use of heating and cooling systems) could provide insights into the variations in energy performance observed and clarify the role of user behavior in passive house efficiency.

The subject of KAPE monitoring were not parameters as air quality or relative humidity nor the user behavior. The building was additionally the subject of a detailed, short-term study carried out by Saint Gobain company. The measurements included indoor air relative humidity and CO2 concentration, as well as the thermal conductivity coefficient of the envelope. The results confirmed the achievement of a high quality of indoor environment and insulation of the building elements. However, the results are not publicly available and cannot be included in this publication.

An additional section 2.4 Limitations of the methodology and measurements, has been included in the article.

3. The potential for PV integration is mentioned, but a more detailed analysis (e.g., potential energy savings, cost-benefit analysis, feasibility of installation) could provide a practical outlook on achieving net-zero or positive energy status, making the study more applicable for readers interested in PV solutions.

This issue is explained in additional chapter 5. Photovoltaic system. It includes the selection of PV system for the building.

4. Adding graphical representations for year-over-year comparisons, such as heat maps or trend lines of indoor temperatures and energy consumption, could make the findings more accessible and visually engaging for readers.

A Figure 15: Year-over-year comparisons of final energy consumption balance (1.5mb firewood) and description of comparison was added below.

5. The findings in the paper are presented clearly and descriptively, providing a solid overview of the observed comfort levels and energy consumption patterns. To further strengthen the robustness of these findings, however, it may be beneficial to incorporate additional statistical validation. Including statistical tests or calculating error margins for key results could enhance the reliability of the conclusions, helping to confirm that the observed patterns in comfort and energy efficiency are both consistent and statistically significant. This added layer of analysis would likely increase confidence in the study's outcomes, providing readers with a stronger basis for understanding the consistency and impact of passive building performance.

The precise assessment of two weeks external weather events (3.1 Assessment of Indoor Thermal Comfort) was expanded and include statistical analysis for all years and periods. This analysis led to additional conclusions and observations.

6. To provide additional context and strengthen the introduction, it might be helpful to include a brief discussion on the broader issue of greenhouse gas (GHG) emissions resulting from the energy sector. Highlighting the environmental impact of GHG emissions, particularly in relation to residential energy consumption, would underscore the importance of sustainable building practices like passive house design. For this purpose, I suggest consulting the following published articles on the topic (please note that these references are purely for guidance and are not mandatory for citation):

• Ciancio, V., Salata, F., Falasca, S., Curci, G., Golasi, I., & Wilde, P. (2020). Energy demands of buildings in the framework of climate change: An investigation across Europe. Sustainable Cities and Society. https://doi.org/10.1016/j.scs.2020.102213.
• E. De Cristo, L. Evangelisti, G. Battista, C. Guattari, R. De Lieto Vollaro, F. Asdrubali, Annual Comparison of the Atmospheric Urban Heat Island in Rome (Italy): An Assessment in Space and Time, Buildings 13 (2023). https://doi.org/10.3390/buildings13112792.

Thank you for this comment. Additional literature studies were conducted and 8 additional sources were cited in the article.

7. The paper presents valuable insights into the long-term performance of a passive house, particularly through real-world data on energy consumption and thermal comfort. However, the methodological approach, focusing on descriptive analysis of historical data, could be viewed as somewhat conventional within the field of sustainable building research. Passive building performance studies often employ similar monitoring approaches, and many have already established the effectiveness of passive design principles in maintaining comfort and reducing energy consumption. To increase the originality of the work, the authors might consider expanding their approach. For example, integrating more advanced analytical methods would add depth and innovation to the study. Additionally, exploring new variables, such as air quality or humidity levels, or examining user behavior in relation to building performance, could provide unique insights that are less commonly addressed in passive house research. These additions would help distinguish the study within the existing body of literature, offering readers a fresh perspective on passive building efficacy in diverse conditions.

The paper is not aiming to be another theoretical consideration of passive construction, which has already been the subject of numerous articles. Nor is it intended to generalize anything to other buildings. It is an analysis of a specific case and shows the effects of a correct and thoughtful approach to the issue of designing and the process of constructing a passive building. The achieved standard of thermal protection reduces the required power of the heating system to a minimum. What kind of heating system is used in the building is practically of little importance from an user perspective, because it does not affect much the operating costs. However, it has a very large impact on investment costs. The embodied carbon footprint associated with building a system using a heat pump in comparison to direct electric heating, will also be larger. This is one the basic conclusion of the analysis of this case, making a contribution to the issue of passive construction.

It is worth noting that the cost of construction of the building at the date of completion in 2016 was no higher than the cost of constructing a standard building, due primarily to two factors. First of all, thanks to the simple architecture and design. Secondly due to the lack of need for an expensive, traditional heating system. Originally, it was planned to use a ground source heat pump and water floor heating. The cost of such solution accounted for about 17% of the construction cost. Eventually, after considering the energy modelling results and economic analysis, this cost was avoided (electric floor heating was chosen), significantly reducing construction costs.

Unfortunately, the research did not include more parameters of the indoor environment or surveys of residents. At the same time, the research aimed to analyze the normal, standard behavior of residents who are not constrained by additional responsibilities. An additional section 2.4 Limitations of the methodology and measurements, has been included in the article.

8. Typos must be checked and corrected.

Errors were corrected.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I would like to thank the authors for having taken some of my comments into account.

Author Response

Dear Reviewer

Thank you very much for positive opinion and comments. Extended literature studies were included in the paper. 11 new articles were cited in chapter 1.2.  All changes were made in track changes mode.

Regards

Authors

Reviewer 2 Report

Comments and Suggestions for Authors

The changes introduced by the Authors in response to my comments have significantly enhanced the scientific value of the work and clarified key issues that previously raised my concerns. The Authors have included additional information on different energy standards in section 1.1. I particularly appreciate the expanded analysis of the building’s technical systems and the addition of a new chapter dedicated to the photovoltaic system, which enriches the article and highlights its practical significance. As a case study, the work now more clearly emphasizes its contribution to advancing knowledge in the field of passive construction.

However, I strongly recommend further expanding the literature review.

Author Response

Dear Reviewer

Thank you very much for positive opinion and comments. Extended literature studies were included in the paper. 11 new articles were cited in chapter 1.2.  All changes were made in track changes mode.

Regards

Authors

Reviewer 3 Report

Comments and Suggestions for Authors

Substantial revisions have been made to the manuscript, significantly enhancing its quality and scientific rigor. In my opinion, the paper is now ready for publication.

Author Response

Dear Reviewer

Thank you very much for positive opinion and comments. Extended literature studies were included in the paper. 11 new articles were cited in chapter 1.2.  All changes were made in track changes mode.

Regards

Authors