Mason & Main Building B
Multifamily Housing in Seattle, WA · 1020 S MAIN ST · 98144
At a glance
Mason & Main Building B is a 228,345-square-foot multifamily housing building at 1020 S MAIN ST in Seattle, Washington, built in 2021. In its 2025 Seattle benchmarking disclosure it reported an ENERGY STAR score of 100 out of 100 (grade A), a site energy-use intensity of 17.5 kBtu/ft² and 23 tCO₂e of greenhouse-gas emissions. That score is higher than 88% of the 1,652 scored multifamily housing buildings in Seattle.
Seattle Energy Benchmarking Ordinance (SMC 22.920) · reporting year 2025
Benchmarking record
| Field | Value |
|---|---|
| ENERGY STAR score | 100 (band A) |
| Site EUI | 17.5 kBtu/ft² |
| Source EUI | 49.0 kBtu/ft² |
| GHG emissions | 23 tCO₂e |
| GHG intensity | 0.1 kgCO₂e/ft² |
| Electricity | 1,178,603 kWh |
| Gross floor area | 228,345 sq ft |
| Source record | seattle:50885:2025 |
The disclosure history
Year over year
| Year | Score | Δ | Site EUI | GHG emissions |
|---|---|---|---|---|
| 2025latest | 100 | ±0 | 17.5 kBtu/ft² | 23 tCO₂e |
| 2024 | 100 | 20.0 kBtu/ft² | 83 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.
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Location
- Address
- 1020 S MAIN ST
- City
- Seattle
- State
- Washington
- ZIP
- 98144
- Coordinates
- 47.60047, -122.31854
Within ~1 km
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See also: most efficient in Seattle · biggest emitters
How does Mason & Main Building B compare with other multifamily housing buildings in Seattle?
The latest disclosures cover 1,971 multifamily housing buildings in Seattle, out of 3,871 buildings citywide. Mason & Main Building B's ENERGY STAR score of 100 compares with an average of 83 across the 1,652 that report a score; it scores higher than 88% of them. Its site EUI of 17.5 kBtu/ft² is about half of the average of 34.9 kBtu/ft² — it uses less energy per square foot than the typical building in that group. Its emissions intensity of 0.1 kgCO₂e/ft² is about 86% below the group average of 0.7 kgCO₂e/ft².
At 228,345 sq ft, it is about 164% above the average floor area of 86,468 sq ft for those buildings. It was built in 2021, 38 years later than the group's average year built (1983). 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.
How has Mason & Main Building B's energy performance changed over time?
BuildingCensus holds 2 Seattle disclosures for Mason & Main Building B, covering report years 2024–2025. Its ENERGY STAR score was 100 in both 2024 and 2025. Site EUI moved from 20.0 kBtu/ft² (2024) to 17.5 kBtu/ft² (2025), a 13% decrease. Reported emissions went from 83 tCO₂e to 23 tCO₂e over the same span (down 72%).
What does an ENERGY STAR score of 100 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: 100 is the top of the scale. BuildingCensus bands the score into report-card grades; 100 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. Mason & Main Building B's 17.5 kBtu/ft² across 228,345 sq ft works out to about 4 billion Btu (1,171 MWh-equivalent) in 2025. Its source EUI of 49.0 kBtu/ft² also counts the energy lost generating and delivering that power, which is why it is higher. The disclosure also reports 1,178,603 kWh of electricity for the year.
Which law requires Mason & Main Building B to report its energy use?
Mason & Main Building B 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:50885:2025). 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 multifamily housing buildings in Seattle
- International District Village Square 2· 228,288 sq ft · score 77 (B)
- Victor Apartments· 228,094 sq ft · score 98 (A)
- Youngstown Flats Apts· 227,672 sq ft · score 100 (A)
- Galleria· 227,233 sq ft · score 92 (A)
- Batik Apartments· 226,256 sq ft · score 100 (A)
- Accolade· 226,051 sq ft · score 94 (A)
- Multifamily Housing buildings in Seattle· 1,971 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 Mason & Main Building B's energy grade?
Mason & Main Building B scores 100 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 Mason & Main Building B use?
Its 2025 site energy-use intensity was 17.5 kBtu/ft² (49.0 kBtu/ft² source) across 228,345 sq ft, including 1,178,603 kWh of electricity.
What are Mason & Main Building B's carbon emissions?
Mason & Main Building B reported 23 tCO₂e of greenhouse-gas emissions (0.1 kgCO₂e/ft²) for 2025.
Where is Mason & Main Building B?
Mason & Main Building B is at 1020 S MAIN ST, in Seattle, Washington 98144. Its coordinates are 47.60047, -122.31854 (latitude, longitude), as published in the Building Energy Benchmarking file.
How big is Mason & Main Building B and when was it built?
Mason & Main Building B has 228,345 sq ft of gross floor area, as reported in its 2025 disclosure. The disclosure lists 2021 as its year built. It is classed as multifamily housing.
Is Mason & Main Building B 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, “Mason & Main Building B, Seattle, Washington — 2025 benchmarking disclosure”, https://buildingcensus.com/buildings/seattle/mason-main-building-b-80fd7b67 (data as of October 2, 2026).