CORNERSTONE MGMT:21 SOUTH WILLIAM STREET
Multifamily Housing in New York City, NY · 21 SOUTH WILLIAM STREET · 10004
At a glance
CORNERSTONE MGMT:21 SOUTH WILLIAM STREET is a 23,980-square-foot multifamily housing building in New York City, New York, built in 1928. In its 2024 New York City benchmarking disclosure it reported an ENERGY STAR score of 99 out of 100 (grade A), a site energy-use intensity of 31.1 kBtu/ft² and 70 tCO₂e of greenhouse-gas emissions. That score is higher than 88% of the 22,829 scored multifamily housing buildings in New York City.
Local Law 84 (LL84) · reporting year 2024
Benchmarking record
| Field | Value |
|---|---|
| ENERGY STAR score | 99 (band A) |
| Site EUI | 31.1 kBtu/ft² |
| Source EUI | 68.7 kBtu/ft² |
| GHG emissions | 70 tCO₂e |
| GHG intensity | 2.9 kgCO₂e/ft² |
| Electricity | 144,830 kWh |
| Natural gas | 2,510 therms |
| Water use | 2,980 kgal |
| Gross floor area | 23,980 sq ft |
| Source record | nyc:56210293:2024 |
Compliance context
Local Law 84 (LL84)
Under Local Law 97, buildings over 25,000 sq ft face carbon caps with fines of $268 per metric ton of CO₂e over the limit, phasing in from 2024.
Ownership
No owning organisation shown. Names of private individuals in the disclosure are not published here.
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Location
- Address
- 21 SOUTH WILLIAM STREET
- City
- New York City
- State
- New York
- ZIP
- 10004
- Coordinates
- 40.70451, -74.01074
Within ~1 km
Nearby benchmarked buildings
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- One Liberty Plaza (149 BROADWAY)score 75
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- 28 Libertyscore 59
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- 120 Broadway Holdings, LLCscore 78
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See also: most efficient in New York City · biggest emitters
How does CORNERSTONE MGMT:21 SOUTH WILLIAM STREET compare with other multifamily housing buildings in New York City?
The latest disclosures cover 33,022 multifamily housing buildings in New York City, out of 48,310 buildings citywide. CORNERSTONE MGMT:21 SOUTH WILLIAM STREET's ENERGY STAR score of 99 compares with an average of 63 across the 22,829 that report a score; it scores higher than 88% of them and lower than 10%. Its site EUI of 31.1 kBtu/ft² is about 58% below the average of 74.9 kBtu/ft² — it uses less energy per square foot than the typical building in that group. Its emissions intensity of 2.9 kgCO₂e/ft² is about 44% below the group average of 5.2 kgCO₂e/ft².
At 23,980 sq ft, it is about 76% below the average floor area of 100,951 sq ft for those buildings. It was built in 1928, 24 years earlier than the group's average year built (1952). Across all 24 jurisdictions BuildingCensus covers, the 59,945 multifamily housing buildings average an ENERGY STAR score of 70 and a site EUI of 59.0 kBtu/ft².
What does an ENERGY STAR score of 99 mean?
ENERGY STAR scores run from 1 to 100 and are computed by the EPA's Portfolio Manager as a percentile against similar buildings nationwide, adjusted for climate, size and use: a score of 99 means the building performs better than about 99% of its national peers. BuildingCensus bands the score into report-card grades; 99 falls in band A — high performer (85–100). Scores of 75 or higher meet the threshold for ENERGY STAR certification; certification itself is a separate, verified application that the disclosure does not record. In New York City, 43% of scored buildings are at 75 or above.
Site energy-use intensity (EUI) is the energy a building uses on site in a year divided by its floor area, in thousand Btu per square foot — lower is more efficient. CORNERSTONE MGMT:21 SOUTH WILLIAM STREET's 31.1 kBtu/ft² across 23,980 sq ft works out to about 0.7 billion Btu (219 MWh-equivalent) in 2024. Its source EUI of 68.7 kBtu/ft² also counts the energy lost generating and delivering that power, which is why it is higher. The disclosure also reports 144,830 kWh of electricity, 2,510 therms of natural gas and 2,980 thousand gallons of water for the year.
Which law requires CORNERSTONE MGMT:21 SOUTH WILLIAM STREET to report its energy use?
CORNERSTONE MGMT:21 SOUTH WILLIAM STREET reports under Local Law 84 (LL84), the legal basis of New York City's Energy and Water Data Disclosure program, which publishes each covered building's annual benchmarking results. The record shown here is the report-year 2024 disclosure (source record nyc:56210293:2024). Under Local Law 97, buildings over 25,000 sq ft face carbon caps with fines of $268 per metric ton of CO₂e over the limit, phasing in from 2024.
More multifamily housing buildings in New York City
- 10 15 Realty LLC : 18-20 East 84th St.· 23,948 sq ft
- 580 Central Avenue AKA 155 Eldert Street· 23,940 sq ft · score 60 (C)
- 85 WEST 166 STREET· 23,913 sq ft
- 126 La Salle St· 23,886 sq ft · score 28 (D)
- CitiLeaf Housing· 23,849 sq ft · score 7 (D)
- Melrose Park HDFC-689 Melrose Avenue· 23,842 sq ft · score 4 (D)
- Multifamily Housing buildings in New York City· 33,022 benchmarked
- All New York City benchmarked buildings· Local Law 84 (LL84)
- Most efficient large buildings in New York City
- Least efficient large buildings in New York City
- Biggest emitters in New York City
Frequently asked questions
What is CORNERSTONE MGMT:21 SOUTH WILLIAM STREET's energy grade?
CORNERSTONE MGMT:21 SOUTH WILLIAM STREET scores 99 out of 100 on ENERGY STAR — band A, high performer (85–100) — in its 2024 New York City disclosure. Scores are national percentiles against similar buildings; 75+ qualifies for ENERGY STAR certification.
How much energy does CORNERSTONE MGMT:21 SOUTH WILLIAM STREET use?
Its 2024 site energy-use intensity was 31.1 kBtu/ft² (68.7 kBtu/ft² source) across 23,980 sq ft, including 144,830 kWh of electricity and 2,510 therms of natural gas.
What are CORNERSTONE MGMT:21 SOUTH WILLIAM STREET's carbon emissions?
CORNERSTONE MGMT:21 SOUTH WILLIAM STREET reported 70 tCO₂e of greenhouse-gas emissions (2.9 kgCO₂e/ft²) for 2024.
Where is CORNERSTONE MGMT:21 SOUTH WILLIAM STREET?
CORNERSTONE MGMT:21 SOUTH WILLIAM STREET is in New York City, New York 10004. Its coordinates are 40.70451, -74.01074 (latitude, longitude), as published in the Energy and Water Data Disclosure file.
How big is CORNERSTONE MGMT:21 SOUTH WILLIAM STREET and when was it built?
CORNERSTONE MGMT:21 SOUTH WILLIAM STREET has 23,980 sq ft of gross floor area, as reported in its 2024 disclosure. The disclosure lists 1928 as its year built. It is classed as multifamily housing.
Is CORNERSTONE MGMT:21 SOUTH WILLIAM STREET covered by Local Law 84 (LL84)?
Yes — it appears in the 2024 Energy and Water Data Disclosure disclosure, which lists the buildings reporting under Local Law 84 (LL84).
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About this data
Source: Energy and Water Data Disclosure (Local Law 84 (LL84)), as published October 2, 2026. See the methodology for how records are matched, cleaned and scored.
Cite as: BuildingCensus, “CORNERSTONE MGMT:21 SOUTH WILLIAM STREET, New York City, New York — 2024 benchmarking disclosure”, https://buildingcensus.com/buildings/new-york-city/cornerstone-mgmt-21-south-william-street-b0bae253 (data as of October 2, 2026).