Example 1

Mixed-use office building in Greensboro, North Carolina

Property description

This vintage-1971 property, located in downtown Greensboro, NC, was the subject of an in-depth case study describing the facility, various energy efficiency improvements that were made, and associated outcomes (IMT 2015a). While this is an 88,000 square foot building with 21 tenants, the owner issues gross leases and is thus responsible for and interested in energy costs.

Energy features and data

According to the case study, “This project is a leading example of how energy modeling can be used to identify and plan retrofits over time. A 2011 energy evaluation identified potential retrofits that if fully undertaken would reduce energy use by 26 percent. Self-Help has implemented many of these measures, including a comprehensive lighting retrofit and upgrades to its HVAC system with a total investment of $50,926. Retrocommissioning and a tenant energy awareness and training program was also implemented. Within a year of the retrofits, the property achieved $8,111 in annual energy savings and a 19 percent reduction in site energy use. In addition, the savings created a better environment for tenants and contributed directly to net operating income, creating immediate capitalized value that represents a multiple of 1.8 times the original investment. Over a projected 20 year duration, the project will yield an unleveraged internal rate of return (IRR) of 18 percent, an annual return on investment (ROI) of 13 percent, and a net present value (NPV) of $80,818.”

Improved comfort and lighting conditions were considered an added benefit of the energy retrofit process.

The median site EUI of this building was determined by entering raw energy data into the Portfolio Manager tool (see below). Prior it its retrofit in 2012, the subject building had an EUI of 92 kBTU/sq ft-y. Following the retrofits, the result was 74 kBTU/sq ft-year, corresponding to 19% site energy savings and 6.4% energy cost savings. The most significant energy savings took place in fuel (38%), compared to electricity (13%).

Data Quality and Other Considerations

The energy Measurement and Verification (M&V) report and energy modeling used to determine the savings potential was funded by the North Carolina State Energy Office, thus benefiting from third-party not-for-profit oversight. The overall case study was developed by a different not-for-profit entity known as the Institute for Market Transformation.

Note that the Portfolio Manager analysis was not performed by a registered engineer, and thus third-party verification of the inputs was not obtained. As with any rental property owner, certain inputs to Portfolio Manager (particularly occupancy and numbers of computers) change often and are hard to track.

ANALYSIS: Building Performance Database

The BPD makes it possible to put the pre- and post-retrofit energy use in context with other buildings in the area. BPD currently contains 1,692 buildings in North Carolina. By tightening the filters to include only buildings in Greensboro yields a sample of 88. Of these 33 are offices and relevant retail use types.

The Figure shows the results of these buildings and our overlay of the EUI for the subject property. Prior to the retrofits, the building performed significantly below the median for this peer group, rising to slightly better than median after the energy-saving improvements. This analysis shows that material reductions in energy consumption were made, although the building was not highly energy efficient following the work.

We can see from the scatter plot that there is no particular correlation among these buildings of EUI and overall building size. Thus the sample does not need to be further reduced to ensure a homogenous peer group. Post-retrofit electricity EUIs were slightly below median for the sample (56 kBtu/sf-y vs 58 kBtu/sf-y), while gas EUIs were above (12 kBtu/sf-y vs 10 kBtu/sf-y)

ANALYSIS: Portfolio Manager

Portfolio Manager was used to track energy use changes throughout this buildings energy retrofit process. This places the building in context with a peer group drawn from the statistical sample of buildings provided by the Commercial Buildings End Use Survey (CEUS), performed periodically by the U.S. Department of Energy (DOE 2015). Decreases in vacancy rates drove energy use upwards between 2008 and 2010.

Pre-retrofit energy use was consistent with its relatively poor Portfolio Manager score of 33 (75 is a passing score for earning an Energy Star rating). Following the retrofit (2012), the performance level corresponded to an improvement in Energy Star score to 55. Note, however, that the analysis was not performed by a registered engineer, and thus third-party verification of the inputs was not obtained. The first two following charts show the latest and historical changes in Score, while the subsequent table brackets the pre- and post-retrofit years.

These results are internally consistent with what we learned from BPD, i.e. the pre-retrofit building performed well below average while following the energy upgrades, performance increased such that the building was in the upper half of the distribution.

ANALYSIS: Building Asset Score

The Building Asset Score tool was run on this building with data provided by the building owner's Sustainability Director. The tool provides a rating (scale of 1-10, in half-point increments) based on standardized operational assumptions. The building was modeled in one "block" because insufficient data were available to map the various features and systems to each space type (office/retail/basement). While electric resistance heating is used in the perimeter zone, the tool cannot model this type of heating and thus the central plant is assumed to serve the entire building.

The tool assigned a score of 8.5 out of 10. This relatively high rating compared to scores on BPD (the building ranks only slightly better than the median for the sample population) and Portfolio Manager (rating of 55, post-retrofit) (which are based on measured as-used conditions) suggests that energy savings are possible through improved operations and equipment control strategies, i.e., the results for BPD and Portfolio Manager reflect the building as-used whereas the Asset Score standardizes many operating assumptions.. In keeping with this, the Asset Rating corresponds to a site EUI of about 38 kBTU/sf-year, while the actual use (per Portfolio Manager) is about 74 kBTU/sf-year.

Note that when re-running the building using the limited "Lite" data input set, the score increased to 9.0. This presumably traces to differences between actual and defaulted property features. One example is that window area is spread evenly over all four sides with the Lite version, whereas in the actual building glazing is only on the North and West sides (reducing afternoon solar gains that tend to drive up air conditioning costs). In addition, the "Lite" form does not address water heating, and thus the model assumes there is no service hot water supply.

References

Miller, J. 2015. “Valuing Energy Efficiency: 122 North Elm Street, Greensboro, North Carolina.” Institute for Market Transformation, Washington, DC. 6pp. http://www.imt.org/uploads/resources/files/IMT_ValuingEE_Greensboro_FINAL.pdf

U.S. Department of Energy, Commercial Buildings End Use Survey. http://www.eia.gov/consumption/reports.cfm#/T88