Energy Savings Results from Small Commercial Building Retrofits in the US

Round 1

Reviewer 1 Report

Dear Authors, congratulations with this work. I think it is very well designed and also it provides relevant novelties to the related literature field.

Indeed, I agree that focusing on small commercial buildings is a need in terms of filling in the literature gap.

Moreover, implications at both the managerial level and also policy level are important.

As a main concern, I would only ask you to shed even more light by deepening further the policy and managerial implications in the conclusions section, that results quite succinct.

This is one of the major contributions and impacts related to your scientific work, and, thus, deserves to be further emphasized.

In detail, what I am going to expect from the revised conclusion section is:

1) To read which specific policies could be suggested to policy makers, supported by related motivation for those suggested measures. This is even more relevant by considering that the quota of energy consumption for small commercial buldings is really kinda market niche;

2) If and how suggested measures could imply any changes in terms of managerial decision-making processes at the firm level;

3) How suggested policy measures are expected to be related to the respect of sustainability issues and objectives. I mean, could authors provide any indicative expectation in terms of enviornmental impact reduction based on the adoption of policymeasures?

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

Overview:

This paper researches the potential of saving energy in small (<50,000 square feet of floor space) commercial buildings in the U.S. The main focus is on the following.

(1) it identifies the decision criteria used by small commercial building stakeholders that decided to complete an energy retrofit; (2) it identifies the most commonly implemented efficiency measures in small commercial buildings and discusses why this is the case; and (3) it provides empirical evidence about the efficacy of installing single energy efficiency measures (EEMs) compared to packages of EEMs in small commercial buildings by reporting verified energy savings.

Reviewer’s comments:

1. This is an interesting paper on the opportunities of saving energy in small commercial buildings, even though the total energy consumption in this sector is between 8%-10% of US’ primary energy consumption. There is some discrepancy in this 8%-10% figure: the Abstract states 10% whereas the introduction mentions 8%. This error should be clarified.
2. The paper points out barriers to energy efficiency retrofits viz. difficulty in identifying the optimal set of solutions for a specific project due to lack of understanding of the relationships and synergies among energy efficiency measures, cost, and comfort; lack of a dedicated facilities manager to supervise building operations; small commercial buildings view that cost and location are dominant factors. Sustainability or climate change did not seem to be the primary driver; building owners prefer a payback of less than one year. The practical issues facing implementation of energy savings retrofit are suitably captured in the paper.
3. In Fig. 3. Please explain what Cooling-Pumps are and how they differ from Cooling-Equipment.
4. A useful result and one which is being emphasized by policy makers is to estimate the total energy reduction anticipated based on Fig. 2 and the estimated amount of CO₂ reduction. CO₂ reduction is of current interest. The authors should estimate CO₂ reductions for different likely retrofits or at least the CO₂ savings if the most likely retrofits were fully implemented in the small commercial building stock.

Major Revision:

Publish after addressing reviewer’s comments, especially item #4.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Please clarify whether estimates of CO2 mitigation are net or not. Net means the CO2 reduction after accounting for the CO2 produced to manufacture the retrofit materials, and the CO2 released in hauling off material from the retrofitted buildings. This is a VERY important point. 

Why is 0.95% retrofit rate considered very aggressive? At this rate, it will take decades to retrofit small commercial buildings.

Author Response

The authors thank the reviewer for the time spent reviewing our manuscript a second time. To expedite this third review, we show all markup in our revised manuscript. 

 

The carbon savings are net, and we added the word "net" to the text description and the table (see p.14, line 310 and Table 3). The conversion factor we used was for net carbon, based on the EPA's data for national carbon impact of average kWh production.

 

We added in some discussion of pushing the retrofit rate, which only included energy retrofits, higher (p. 15, lines 353-360):

"Finally, such an approach has the potential to increase the retrofit rate to be higher than 1%, which is certainly required to meet urgent climate action goals. The authors note that the renovation rate, which Coffey et al. define as “buildings being renovated for architectural or function purposes” is 4% in the “very aggressive” case [73]. So, if these renovations then included energy retrofits, the overall rate of energy retrofits would climb to nearly 5%, meaning that all buildings would have energy retrofits in two decades, which is certainly more encouraging than the ten decades it would take if only energy retrofits were included in the rate."

Round 3

Reviewer 2 Report

The revision does not answer the reviewer’s earlier comment #4 on quantifying CO2 reduction levels. This can be stated in kg CO₂/year

 

Cooling pumps MUST be replaced with Ground Source Heat Pumps since that is what the authors imply. Cooling Pumps is not a customary way of indicating ground source heat pumps.

Author Response

Reviewer Comment: The revision does not answer the reviewer’s earlier comment #4 on quantifying CO2 reduction levels. This can be stated in kg CO₂/year

Authors' Response: We opted to present CO2 emission reductions in mtCO2 in Table 3, as this is the metric used by the United States Environmental Protection Agency. However, we have updated the text of the manuscript to present kgCO2/year reductions as requested. See lines 316-319 of the manuscript, which state, "Table 3 illustrates that even with a “very aggressive” energy retrofit rate of .95%, the carbon emissions reductions associated with small commercial building retrofits are relatively small, ranging from 662,000 kgCO2/year for 5% energy savings to 2,647,000 kgCO2/year for 20% energy savings."

Reviewer Comment: Cooling pumps MUST be replaced with Ground Source Heat Pumps since that is what the authors imply. Cooling Pumps is not a customary way of indicating ground source heat pumps.

Authors' Response: Thank you for this comment. "Cooling -- Pumps" is the option for case study respondents on the 2030 District case study portal. As such, the authors felt it was important to maintain that language in Table 1. However, we have added a table note where we explain that "Cooling -- Pumps" should be understood as ground source heat pumps (see lines 151-152 of the manuscript, "This is more commonly referred to as a ground source heat pump. However, to maintain consistency with the categorization found in [32], the authors list “Cooling – Pumps” in the table"). Similarly, because "Cooling -- Pumps" is the language in Table 1, based on the source's categorization scheme, we left "Cooling -- Pumps" in Figure 3, though since none of the case studies installed ground source heat pumps, the value remains zero. We are willing to change this again, but would appreciate the reviewer's thoughts on how to delineate that "Ground Source Heat Pumps" is not an option for the case study entries on the 2030 District portal, so we avoid misrepresenting the source material.

 

 

Author Response File: Author Response.docx

Round 4

Reviewer 2 Report

The authors should explain in a footnote to capture the essence of what they have stated in their response to the reviewer (see quotes below).  This will clarify the distinction between Cooling---Pumps and ground source heat pumps and the source material they utilize in their paper.

 

"Similarly, because "Cooling -- Pumps" is the language in Table 1, based on the source's categorization scheme, we left "Cooling -- Pumps" in Figure 3, though since none of the case studies installed ground source heat pumps, the value remains zero. We are willing to change this again, but would appreciate the reviewer's thoughts on how to delineate that "Ground Source Heat Pumps" is not an option for the case study entries on the 2030 District portal, so we avoid misrepresenting the source material."

The conclusions should also include a few sentences on CO2 emissions reductions in kg CO2/year, since this is an important point for researchers going forward.

Author Response

Thank you for your continued review of our manuscript!

 

We have added the footnote to the discussion of ground source heat pumps as suggested (see line 147). The footnote reads, "The authors use “Cooling – Pumps” in both Table 1 and Figure 3 to maintain consistency with the EEM categorization provided in the 2030 Districts case study portal [32]. Readers should interpret “Cooling – Pumps” as ground source heat pumps."

We have also added three sentences to the Conclusion (lines 377-384) to discuss the carbon impacts of small commercial building retrofits:

Indeed, taking an integrated approach to energy retrofits increases the energy efficiency as well as the carbon emissions, thus supporting achieving energy and carbon reduction goals with a single intervention. If small commercial buildings achieve a 20% energy savings, and .95% of the small commercial stock is retrofit each year, a savings of 2,647,000 kgCO₂/year would result. If the retrofit rate can be increased, the carbon emissions reductions will further increase, highlighting the paramount importance of convincing more small commercial building owners to implement energy retrofits.

In the spirit of the second comment, we addressed carbon savings in the abstract, adding lines 33-36, which read:

Finally, this research documents the improved savings, in the small commercial buildings market, associated with a more integrated package of EEMs compared to a single-system approach, achieving approximately 10% energy savings for a single-system approach and more than 20% energy savings for integrated approaches. These savings translate to CO₂ savings of 1,324,000 kgCO₂/year to 2,647,000 kgCO₂/year, respectively, assuming small commercial buildings are retrofit at a rate of .95% of the stock annually.