A Comparative Life Cycle Assessment of Reusable and Disposable HVAC Air Filters

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for the opportunity to review this manuscript. The manuscript addresses a relevant topic aligned with current discussions on sustainability, circular economy, and life cycle assessment. However, the manuscript still presents important limitations related to its theoretical foundation, methodological transparency, the robustness of the adopted assumptions, and the analytical depth of the discussion of the results. I have provided some suggestions to the authors. Therefore, my recommendation is a Major Revision.

The Introduction adequately highlights the importance of indoor air quality, HVAC systems, and the environmental concerns associated with disposable and reusable filters. However, the contextualization remains overly descriptive and insufficiently integrated. The authors should strengthen the logical connection among sustainable buildings, circular economy principles, HVAC filtration technologies, and Life Cycle Assessment (LCA), developing a more coherent theoretical foundation that clearly justifies the need for this research.

Suggestion: Add a concluding synthesis paragraph that explicitly links these concepts and explains how they collectively motivate the study.

The manuscript states that limited literature exists on the LCA of reusable filters, but it does not systematically demonstrate which studies are available, their limitations, or the specific novel contribution of the present study compared to previous research.

Suggestion: Include a concise literature comparison table summarizing previous studies, their limitations, and the specific gap addressed by this research.

The main research objective should be explicitly stated in a dedicated paragraph at the end of the Introduction using clear and concise language. The expected theoretical and practical contributions should also be clearly presented, as they are currently not sufficiently evident.

Suggestion: Add a final paragraph to the Introduction clearly stating the research objective and the expected theoretical and practical contributions.

The methodology presents important weaknesses related to transparency and replicability. In lines 117–125, the authors define eight operational cycles as the functional unit but do not provide a robust technical justification for this choice. It is unclear whether this value is based on durability testing, manufacturer specifications, or empirical observations. Since this assumption directly influences the results, its definition should be justified in greater detail.

Suggestion: Explicitly justify the eight-cycle assumption and provide supporting evidence from technical tests, operational data, or manufacturer specifications.

The absence of a formal inventory data quality assessment is also noteworthy. Although the databases and operational assumptions are described, no evaluation of temporal, geographical, or technological representativeness is provided. A data quality assessment following LCA best practices is recommended.

Suggestion: Include a data quality assessment addressing temporal, geographical, and technological representativeness of the inventory data.

The methodology also mentions sensitivity and circularity analyses; however, it remains unclear how these analyses were conducted, which scenarios were evaluated, and which variables were modified. These methodological procedures should be described in greater detail before presenting the results.

Suggestion: Clearly describe the evaluated scenarios, modified variables, and procedures used in the sensitivity and circularity analyses.

In the Results section, the authors adequately present the initial comparison between reusable and disposable systems. However, the discussion would benefit from a more critical interpretation of the findings by comparing them with similar LCA studies involving filtration systems, reusable products, or circular economy strategies.

Suggestion: Expand the discussion by comparing the findings with results reported in previous LCA studies and explaining major similarities or discrepancies.

Considering that much of the environmental advantage of the reusable filter depends on the number of reuse cycles, it would be particularly valuable to present a detailed environmental break-even analysis, identifying the number of reuse cycles at which the reusable system effectively outperforms the disposable alternative across the different impact categories.

Suggestion: Include a break-even analysis identifying the minimum number of reuse cycles required for the reusable filter to achieve environmental advantages over the disposable alternative.

In the final sections, the authors emphasize the environmental benefits of reusable filters; however, the discussion of practical implications remains superficial. The manuscript would benefit from addressing operational feasibility, reverse logistics costs, market acceptance, maintenance requirements, and implementation limitations in different use contexts. These aspects are essential for translating environmental findings into practical recommendations.

Suggestion: Expand the practical implications section by discussing implementation challenges, operational requirements, and potential barriers to adoption.

Furthermore, the theoretical contributions of the study are not clearly articulated. Although the manuscript provides a relevant applied contribution, it does not clearly explain how the findings advance scientific knowledge in LCA, circular economy, or sustainable HVAC systems. A dedicated subsection highlighting both theoretical and practical contributions is recommended.

Suggestion: Add a dedicated subsection explicitly outlining the study’s theoretical and practical contributions.

Author Response

Please see attached.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript presents a cradle-to-grave Life Cycle Assessment (LCA) comparing a reusable HVAC air filter (Delta M DME11 4043) with conventional disposable HVAC filters over eight equivalent operational filtration cycles. The authors conclude that the reusable filter reduces global warming potential by approximately 46% over the defined functional unit, although carcinogenic impacts remain elevated due to the material intensity of durable filter construction. The work is timely and relevant to sustainable building operations and circular economy objectives, and the manuscript is generally well-organized. However, following points need to be clarified in the revised manuscripts before it is considered to be accepted.

1. The study assumes that the reusable filter maintains MERV 11 filtration performance throughout all eight reuse cycles. However, no experimental evidence is provided to substantiate that the filtration efficiency of the reusable polyester media is preserved after repeated washing and refurbishment. The authors should either provide empirical data on post-wash filtration performance or explicitly discuss this as a limitation and explore its implications through sensitivity analysis.

2. The study does not account for differences in pressure drop between the reusable and disposable filter designs. Pressure drop directly affects fan energy consumption in HVAC systems and can be a significant contributor to operational environmental impacts. If the reusable filter exhibits a different pressure drop profile (especially after repeated washing), this could substantially alter the comparative results. The authors should either include operational energy use within the system boundary or provide a clear justification for its exclusion.

3. Absence of uncertainty analysis. Given the significant assumptions involved—particularly for the disposable filter modeling, transportation distances, and washing parameters—the study would benefit greatly from a formal uncertainty analysis. This would allow the authors to quantify the confidence intervals around their reported impact reductions and provide readers with a clearer understanding of the reliability of the conclusions.

5. The study considers only landfill disposal and material recycling as end-of-life options. Given that the reusable filter contains significant quantities of PVC (0.616 kg) and polyester (0.350 kg), incineration with energy recovery should also be evaluated, as it is a common end-of-life pathway for polymeric materials in many jurisdictions. Expanding the end-of-life scenarios would provide a more comprehensive assessment.
6. Several figures (particularly Figures 6–7) should be improved in resolution and clarity to ensure that axis labels, legends, and data values are legible. The confidence intervals should be included where applicable.
7. It is recommended that relevant literature on air filtration technology be included in the introduction to strengthen the argument supporting the findings of this study. (e.g., Advanced Materials, 2020, 32, 2002361; Materials Today Advances, 2021, 9, 100134).

Author Response

Please see attached.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

At the backdrop of "dual carbon" goals and the circular economy, conducting a Life Cycle Assessment (LCA) of reusable versus disposable HVAC air filters is highly significant. The following questions are provided for reference:

1. This research was funded by the Mitacs Business Strategy Internship. There are potential conflicts of commercial interest.
2. There is a lack of horizontal comparison with reusable filters from other brands. Therefore, the results of this study are more akin to an evaluation of the specific product under investigation, and the generalizability of the research conclusions is somewhat limited. The authors should note this point.
3. What is the rationale for assuming seven refurbishment cycles for the reusable filter in this study? Could the authors provide inspection data on filtration efficiency after repeated cleaning, or evidence demonstrating whether efficiency degradation occurs? Likewise, is the replacement interval for the disposable filter grounded in manufacturer specifications? The relevant basis should be explicitly stated in the manuscript.
4. In the comparison, the reusable system includes detailed accounting for reverse logistics, cleaning, detergents, wastewater treatment, and packaging tape replacement. However, the corresponding disposable system evaluation does not explicitly clarify whether installation waste and packaging disposal for each replacement are included, and assumes that "installation activity energy consumption is negligible." This represents an inconsistency in the comparison.
5. The current conclusion that "reusable HVAC filtration systems can significantly reduce long-term environmental burdens" should be accompanied by appropriate qualifying conditions, such as "under the assumption of seven effective cleaning cycles in this study..." or "within the context of the Ontario provincial grid and waste management infrastructure..." etc.
6. Could the authors propose usage guidelines based on the results, such as specifying optimal cleaning frequency, providing standardized cleaning protocols (water quality requirements, drying conditions, inspection criteria), and establishing end-of-life determination standards (when should a filter be retired rather than continue being cleaned)? Alternatively, could the authors offer recommendations in this regard.

Author Response

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Author Response File: Author Response.docx

Reviewer 4 Report

Comments and Suggestions for Authors

Comments on sustainability-4400537：

This study carries out a cradle-to-grave comparative life cycle assessment (LCA) in accordance with ISO 14040 and ISO 14044 standards, adopting the TRACI 2.1 environmental impact evaluation method. Taking the provision of equivalent filtration service over eight operational cycles as the functional unit, it compares the full-life environmental performance between the reusable Delta M MERV 11 HVAC air filter and eight conventional disposable fiberglass filters. Relying on first-hand manufacturing and operation data from the manufacturer together with the Ecoinvent 3.9.1 database and SimaPro v9.5 software, the research establishes life cycle inventory models covering the whole stages including raw material production, assembly, transportation, washing and reuse, reverse logistics and end-of-life disposal. Although the reusable filter brings higher initial environmental burdens due to durable structural materials such as PVC frames and galvanized steel mesh in a single service cycle, after seven times of recycling and cleaning, its global warming potential is reduced by 46% compared with disposable filters, with remarkable improvements in most environmental impact indicators such as smog formation, acidification, eutrophication and fossil fuel depletion, while only carcinogenic impacts remain relatively higher. End-of-life recycling of PVC and steel components can further cut greenhouse gas emissions and fossil resource depletion. Contribution analysis identifies PVC production, polyester filter media manufacturing and galvanized steel processing as the dominant environmental hotspots. The study verifies that repeated reuse combined with end-of-life material recovery can greatly reduce the long-term environmental loads of HVAC filtration systems, offering theoretical and data support for circular low-carbon building operation and net-zero infrastructure development. My overall opinion is that this paper could be interesting valuable paper if major modifications are implemented.

1. The study fails to distinguish operating conditions of commercial buildings with different air volumes and pressure drops, and energy consumption caused by filter operation is excluded from the system boundary. It only focuses on filter manufacturing and cleaning processes, ignoring long-term power consumption of fans induced by filter pressure drop, which constitutes the core operational carbon emission source of HVAC systems.
2. Only water consumption and detergent usage are accounted for in the cleaning stage, while the full upstream environmental burdens of advanced treatment of cleaning wastewater and detergent production are not quantified. The inventory data for wastewater disposal is oversimplified.
3. The discussion centers primarily on Global Warming Potential (GWP). The issues of elevated carcinogenic and non-carcinogenic impacts are merely briefly mentioned, without in-depth decomposition of the technological nodes generating toxic effects from PVC and galvanized steel, nor analysis of mitigation routes to reduce toxicity.
4. Although PVC, polyester and galvanized steel are identified as environmental hotspots, targeted optimization schemes such as lightweight design, recycled material substitution and low-toxicity steel are not proposed. The hotspot analysis only stays at the identification stage without practical improvement strategies.
5. The model assumes stable filtration performance over all 8 service cycles without accounting for filter service life degradation, reduced cleaning efficiency and deteriorated filtration performance after repeated washing, which may lead to extra replacement cycles. Such idealized modeling assumptions deviate from practical engineering conditions.
6. The field measurement data for the assembly and cleaning of reusable filters are collected within a single year. Fluctuations in power and water consumption caused by seasonal variations and production load changes are not considered, so the life cycle inventory data lack long-term stability verification.
7. The figures only present relative impact proportions without complete raw quantitative values for each scenario, making it impossible for readers to reproduce all calculation results and resulting in insufficient data transparency.
8. The references should be expanded. Some new literatures might be help the authors to further deepen the understanding of reaction mechanism as well as newest developing in this field (Applied Thermal Engineering, 289P3 (2026) 130035 DOI: 10.1016/j.applthermaleng.2026.130035; Colloids and Surfaces A: Physicochemical and Engineering Aspects,2026,141075 DOI: 10.1016/j.colsurfa.2026.141075).

Author Response

Please see attached.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for the new version of the manuscript.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have revised the manuscript according to the suggestions of reviewers, and the manuscript is now ready for publication.

Reviewer 3 Report

Comments and Suggestions for Authors

This study provides a valuable paradigm for circular economy assessment of building products and holds positive significance for advancing sustainable building operations and net-zero targets. The authors have adequately addressed the relevant concerns, and the conclusions are considerably more rigorous following revision. In my opinion, the manuscript has reached the standard for publication, and I recommend its acceptance.

Reviewer 4 Report

Comments and Suggestions for Authors I think the manuscript can be published in its present form.