Example 3

4 Times Square - The Conde Nast Building

Property description

This Manhattan office tower is located Broadway and 42nd Street, New York, and was the first green high-rise building in the United States. The building is 48 stories tall (809 feet), with a floor area of 1.6 million square feet. The project was developed by the Durst Organization, with a total project cost (land excluded) of $270,000,00.

Energy features and data

A so-called "whole-building design" approach was used, emphasizing optimizing multiple interacting systems, with goals of energy efficiency and a healthy indoor environment for occupants. Emphasis was placed on daylighting and specialized controls to minimize the need for electric lighting (including early adoption of LED exit signs), together with low-e windows. A set of various-sized gas-fired absorption chiller plants for heating and cooling were chosen because of their efficiency and flexibility, non-reliance on ozone-depleting refrigerants, and payback of approximately 3 years. Variable-speed drives are used extensively within the HVAC system. Commissioning is employed at roughly five-year intervals to ensure proper installation and operation of mechanical systems. Additional "green" features include the use of "hat-truss" engineering to minimize need for steel in construction, low-emission materials and furnishings, and recycling of 65% of construction debris, and built-in waste chutes to facilitate recycling of office waste. Outside air supply is highly filtered twice that required by New York City standards.

The building also includes significant on-site power generation equipment, including building-integrated solar PV arrays rated at 15kW as well as two, 200-kW natural gas fuel cells that provide useful heat and meet about 10% of the building's annual electricity needs..

The subject building is described in detail in U.S. Department of Energy's High-Performance Buildings Database. The DOE-2 computer analysis work was provided by grants from Rocky Mountain Institute and the New York State Energy Research & Development Agency (NYSERDA). The National Renewable Energy Laboratory has also written a case study.

The building won awards from the AIA, the Alliance to Save Energy in 1999 (Category/title: Star of Energy Efficiency Award) and from New York Construction News in 1998 (Category/title: Commercial Project of the Year). The building is Energy Star certified.

The estimated energy use at the time of design was 67 kBtu/sf-year (site energy) (Cho and Haberl n/d). An analysis of actual energy use in 2008 found the source energy EUI to be 244 kBtu/sf-year and the site energy EUI to be 120 kBtu/sf-year, about one-third lower energy intensity than the 50th percentile value estimated by Portfolio Manager for the same building types and uses (Hinge and Winston 2008).

Data Quality and Other Considerations

Factors leading to energy intensities higher than might otherwise be the case include: The choice to provide higher-than-required outside air supply and associated conditioning costs, extensive exterior lighting associated with the Times Square location, major tenants with significant after-hours operations, energy use associated with roof-mounted broadcast antenna, major corporate cafeterias, sub-optimal efficiencies of the gas-fired absorption chillers.

ANALYSIS: Building Performance Database

The BPD makes it possible to put the pre- and post-retrofit energy use in context with similar buildings in the area. BPD currently contains 941 buildings with energy data in New York City, of which 322 are offices. The median site energy EUI of these comparison buildings is 71 kBTU/sq ft-year.

The figure shows the site energy EUI of these buildings and our overlay of the EUI for the subject property, drawn from the Hinge and Winston (2008). The subject building has a higher EUI than most others in this sample.

We can see from the BPD scatter plot analysis of each building in the distribution 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.

ANALYSIS: Portfolio Manager

Portfolio Manager was used to track energy use changes throughout this building's energy retrofit process. This tool generates the EUI and 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).

While the detailed Portfolio Manager reports could not be obtained, useful summary information is publicly available on the Energy Star website. The subject building maintained a certified Energy Star rating of between 75 and 83 for 6 of the years between 2001 and 2010, suggesting an "culture" of consistent operations and maintenance.

These results are not consistent with the building's poor position with respect to its peers in BPD. Perhaps the data evaluated with Portfolio Manager excluded the above-mentioned ancillary uses.

ANALYSIS: Building Asset Score

The building receives a score of 5.5 out of 10 from the Asset Score tool. The corresponding site EUI is 51 kBtu/sf-year. This is about one-third of the actual EUI recorded by Hinge and Winston (2008), who cite a number of factors that caused energy to be higher than expected (see Data Quality and Other Considerations section, above). This suggests that the usage profile of the building leads to higher energy intensity than would be expected from looking at the building's highly physical characteristics alone. The Asset Score doesn't model several important features of this building, i.e., gas absorption chillers, direct digital control systems, solar PV array, or fuel cells. Because gas-absorption chillers must be modeled as electric, the end-use splits described in the reports will underestimate the contribution of natural gas to total energy use, and significantly over-estimate electricity, and thus source energy.

When rerunning the building using only the "Lite" input form, the score rises slightly to 6.

The most significant energy-saving recommendation from the Asset Score is a chiller upgrade. This reflects the low efficiency of the existing absorption unit. Conversion from fluorescent to LED lighting is also indicated to generate large energy savings.

References

Cho, S. and J.S. Haberl. no date. "A Survey of High-Performance Office Buildings in the United States." Energy Systems Laboratory, Texas A&M University, 8pp. http://esl.tamu.edu/docs/terp/.../ESL-HH-06-07-21.pdf

GBIG. 2015. "Conde Nast Building." http://www.gbig.org/activities/energystar-11809

Hinge, A. and D.J. Winston. 2008. "The Proof is Performance: Does 4 Times Square Measure Up?" High Performance Buildings, Winter, pp. 30-36,

http://www.hpbmagazine.org/attachments/article/12077/08W-The-Proof-Is-Performance.pdf.

U.S. Department of Energy. no date. "4 Times Square: New York City." Highlighting High Performance brochure.

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