At a glance
One Union Square is a 794,592-square-foot office building at 600 UNIVERSITY ST in Seattle, Washington, built in 1980. In its 2025 Seattle benchmarking disclosure it reported an ENERGY STAR score of 95 out of 100 (grade A), a site energy-use intensity of 24.5 kBtu/ft² and 143 tCO₂e of greenhouse-gas emissions. That score is higher than 84% of the 378 scored office buildings in Seattle.
Seattle Energy Benchmarking Ordinance (SMC 22.920) · reporting year 2025
Benchmarking record
| Field | Value |
|---|---|
| ENERGY STAR score | 95 (band A) |
| Site EUI | 24.5 kBtu/ft² |
| Source EUI | 67.1 kBtu/ft² |
| GHG emissions | 143 tCO₂e |
| GHG intensity | 0.2 kgCO₂e/ft² |
| Electricity | 5,511,382 kWh |
| Natural gas | 6,510 therms |
| Gross floor area | 794,592 sq ft |
| Source record | seattle:423:2025 |
The disclosure history
Year over year
| Year | Score | Δ | Site EUI | GHG emissions |
|---|---|---|---|---|
| 2025latest | 95 | +1 | 24.5 kBtu/ft² | 143 tCO₂e |
| 2024 | 94 | ±0 | 25.4 kBtu/ft² | 152 tCO₂e |
| 2023 | 94 | ±0 | 26.4 kBtu/ft² | 156 tCO₂e |
| 2022 | 94 | -1 | 28.9 kBtu/ft² | 203 tCO₂e |
| 2021 | 95 | -4 | 31.1 kBtu/ft² | 156 tCO₂e |
| 2020 | 99 | +1 | 29.2 kBtu/ft² | 161 tCO₂e |
| 2019 | 98 | +1 | 31.5 kBtu/ft² | 173 tCO₂e |
| 2018 | 97 | +8 | 33.8 kBtu/ft² | 192 tCO₂e |
| 2017 | 89 | +1 | 34.5 kBtu/ft² | 185 tCO₂e |
| 2016 | 88 | -2 | 35.2 kBtu/ft² | 186 tCO₂e |
| 2015 | 90 | 33.6 kBtu/ft² | 181 tCO₂e |
Compliance context
Seattle Energy Benchmarking Ordinance (SMC 22.920)
Seattle's Building Emissions Performance Standard (adopted 2023) applies to buildings over 20,000 sq ft: benchmarking verification is due 2027–2030 and initial emissions targets 2031–2035, reaching net zero by 2041–2050, with fines for non-compliance.
Ownership
No owning organisation shown. Names of private individuals in the disclosure are not published here.
Own or manage this building? Claim it to correct the record and get compliance alerts.
Location
- Address
- 600 UNIVERSITY ST
- City
- Seattle
- State
- Washington
- ZIP
- 98101
- Coordinates
- 47.60967, -122.33229
Within ~1 km
Nearby benchmarked buildings
- Columbia Centerscore 90
Office · 1,952,220 sq ft
- Seattle Convention Centerscore —
Convention Center · 1,842,925 sq ft
- Two Union Squarescore 96
Office · 1,605,578 sq ft
Office · 1,599,394 sq ft
- Day 1 Tower And Spheres (Amazon)score 93
Office · 1,599,230 sq ft
- Russell Investments Centerscore 92
Office · 1,592,914 sq ft
See also: most efficient in Seattle · biggest emitters
How does One Union Square compare with other office buildings in Seattle?
The latest disclosures cover 497 office buildings in Seattle, out of 3,871 buildings citywide. One Union Square's ENERGY STAR score of 95 compares with an average of 76 across the 378 that report a score; it scores higher than 84% of them and lower than 12%. Its site EUI of 24.5 kBtu/ft² is about half of the average of 44.8 kBtu/ft² — it uses less energy per square foot than the typical building in that group. Its emissions intensity of 0.2 kgCO₂e/ft² is about 74% below the group average of 0.7 kgCO₂e/ft².
At 794,592 sq ft, it is about 304% above the average floor area of 196,452 sq ft for those buildings. It was built in 1980, 15 years later than the group's average year built (1965). Across all 24 jurisdictions BuildingCensus covers, the 15,264 office buildings average an ENERGY STAR score of 73 and a site EUI of 59.3 kBtu/ft².
How has One Union Square's energy performance changed over time?
BuildingCensus holds 11 Seattle disclosures for One Union Square, covering report years 2015–2025. Its ENERGY STAR score went from 90 in 2015 to 95 in 2025 (+5 points); its best year on file was 2020, at 99. Site EUI moved from 33.6 kBtu/ft² (2015) to 24.5 kBtu/ft² (2025), a 27% decrease. Reported emissions went from 181 tCO₂e to 143 tCO₂e over the same span (down 21%).
What does an ENERGY STAR score of 95 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 95 means the building performs better than about 95% of its national peers. BuildingCensus bands the score into report-card grades; 95 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 Seattle, 69% 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. One Union Square's 24.5 kBtu/ft² across 794,592 sq ft works out to about 19.5 billion Btu (5,705 MWh-equivalent) in 2025. Its source EUI of 67.1 kBtu/ft² also counts the energy lost generating and delivering that power, which is why it is higher. The disclosure also reports 5,511,382 kWh of electricity and 6,510 therms of natural gas for the year.
Which law requires One Union Square to report its energy use?
One Union Square reports under the Seattle Energy Benchmarking Ordinance (SMC 22.920), the legal basis of Seattle's Building Energy Benchmarking program, which publishes each covered building's annual benchmarking results. The record shown here is the report-year 2025 disclosure (source record seattle:423:2025). Seattle's Building Emissions Performance Standard (adopted 2023) applies to buildings over 20,000 sq ft: benchmarking verification is due 2027–2030 and initial emissions targets 2031–2035, reaching net zero by 2041–2050, with fines for non-compliance.
More office buildings in Seattle
- Centurylink: Seattle Bell Plaza· 791,396 sq ft · score 91 (A)
- 1111 3rd Ave Building· 776,762 sq ft · score 85 (A)
- West 8th· 758,043 sq ft · EUI 22.9 kBtu/ft²
- Century Square· 755,000 sq ft · score 83 (B)
- 1700 Seventh Building· 747,747 sq ft · EUI 35.8 kBtu/ft²
- 901 Fifth Avenue· 711,611 sq ft · score 78 (B)
- Office buildings in Seattle· 497 benchmarked
- All Seattle benchmarked buildings· Seattle Energy Benchmarking Ordinance (SMC 22.920)
- Most efficient large buildings in Seattle
- Least efficient large buildings in Seattle
- Biggest emitters in Seattle
Frequently asked questions
What is One Union Square's energy grade?
One Union Square scores 95 out of 100 on ENERGY STAR — band A, high performer (85–100) — in its 2025 Seattle disclosure. Scores are national percentiles against similar buildings; 75+ qualifies for ENERGY STAR certification.
How much energy does One Union Square use?
Its 2025 site energy-use intensity was 24.5 kBtu/ft² (67.1 kBtu/ft² source) across 794,592 sq ft, including 5,511,382 kWh of electricity and 6,510 therms of natural gas.
What are One Union Square's carbon emissions?
One Union Square reported 143 tCO₂e of greenhouse-gas emissions (0.2 kgCO₂e/ft²) for 2025.
Where is One Union Square?
One Union Square is at 600 UNIVERSITY ST, in Seattle, Washington 98101. Its coordinates are 47.60967, -122.33229 (latitude, longitude), as published in the Building Energy Benchmarking file.
How big is One Union Square and when was it built?
One Union Square has 794,592 sq ft of gross floor area, as reported in its 2025 disclosure. The disclosure lists 1980 as its year built. It is classed as office.
Is One Union Square covered by the Seattle Energy Benchmarking Ordinance (SMC 22.920)?
Yes — it appears in the 2025 Building Energy Benchmarking disclosure, which lists the buildings reporting under the Seattle Energy Benchmarking Ordinance (SMC 22.920).
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About this data
Source: Building Energy Benchmarking (Seattle Energy Benchmarking Ordinance (SMC 22.920)), as published October 2, 2026. See the methodology for how records are matched, cleaned and scored.
Cite as: BuildingCensus, “One Union Square, Seattle, Washington — 2025 benchmarking disclosure”, https://buildingcensus.com/buildings/seattle/one-union-square-c6f7abe6 (data as of October 2, 2026).