Portage Bay Flats

How does Portage Bay Flats 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. Portage Bay Flats'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 41.1 kBtu/ft² is about 18% above the average of 34.9 kBtu/ft² — it uses more energy per square foot than the typical building in that group. Its emissions intensity of 1.3 kgCO₂e/ft² is about 86% above the group average of 0.7 kgCO₂e/ft².

At 30,649 sq ft, it is about 65% below the average floor area of 86,468 sq ft for those buildings. It was built in 2014, 31 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 Portage Bay Flats's energy performance changed over time?

BuildingCensus holds 10 Seattle disclosures for Portage Bay Flats, covering report years 2016–2025. Its ENERGY STAR score was 100 in both 2016 and 2025. Site EUI moved from 42.3 kBtu/ft² (2016) to 41.1 kBtu/ft² (2025), a 3% decrease. Reported emissions went from 34 tCO₂e to 40 tCO₂e over the same span (up 19%).

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. Portage Bay Flats's 41.1 kBtu/ft² across 30,649 sq ft works out to about 1.3 billion Btu (369 MWh-equivalent) in 2025. Its source EUI of 73.5 kBtu/ft² also counts the energy lost generating and delivering that power, which is why it is higher. The disclosure also reports 155,784 kWh of electricity and 7,269 therms of natural gas for the year.

Which law requires Portage Bay Flats to report its energy use?

Portage Bay Flats 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:50005:2025). 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.