Millennium Partners has landed a $281 million loan to recapitalize the residential portion of Winthrop Center, the 691-foot skyscraper towering over Boston's Financial District, in what officials are calling the largest deal of its kind ever closed in New England. The financing, provided by Nuveen Green Capital, covers the 317-unit Millennium Residences at Winthrop Center, which sit above the tower's office floors, and swaps out earlier debt for a longer-term, lower-cost loan tied to the property's energy performance.
The loan runs through Property Assessed Clean Energy Massachusetts, the state's version of the C-PACE program, which MassDevelopment administers in consultation with the Massachusetts Department of Energy Resources, according to Banker & Tradesman. Rather than functioning like a typical mortgage, C-PACE debt is repaid through a municipal betterment assessment added directly to the property's local tax bill, with terms stretching up to 20 years, and the obligation automatically passes to future owners if the building is sold. Eighty-nine Massachusetts cities and towns currently participate in the program, per REBusinessOnline.
Millennium Partners said the financing reinforces Winthrop Center's position as one of the world's most environmentally advanced mixed-use developments and allows the company to capitalize on the sustainability investments already made at the site, according to a company statement cited by Bisnow. Christopher M. Jeffries, founder of Millennium Partners, said the company has been committed to creating transformative developments for more than three decades, and that Winthrop Center reflects that commitment while the PACE Massachusetts financing recognizes the tower's energy-efficiency investments, per the same report.
A Passive House Tower Built for This Kind of Debt
Winthrop Center opened in 2023 after Millennium Partners broke ground on the roughly $1.4 billion project in 2018, following a $775 million construction loan secured in October 2020 to build the nearly 1.8 million-square-foot tower on the site of a former city-owned parking garage, according to Architectural Record. Millennium Partners won the municipal RFP competition for the site back in 2016. The 800,000-square-foot office portion was built to the Passive House sustainability standard and is described as the world's largest Passive House office building, the outlet's reporting notes.
That performance isn't just a marketing point. Moody's CRE found in January 2024 that the office space uses roughly 60% to 65% less energy than an average LEED Platinum office building in Boston, and about 150% less than typical Class A commercial space in the city. The tower also houses The Connector, a three-story, 200-foot-long public hall linking Devonshire and Federal streets that serves as a year-round gathering space, per Architectural Record.
BERDO Pressure and a Booming National Market
The efficiency numbers matter under Boston's Building Emissions Reduction and Disclosure Ordinance, known as BERDO 2.0, which imposes mandatory greenhouse gas emissions caps on commercial buildings over 35,000 square feet starting in 2025. Non-compliant buildings face penalties of $1,000 per day or $234 per metric ton of carbon above permitted limits, according to Envigilance, and the ordinance mandates net-zero carbon emissions citywide by 2050. High-performance buildings like Winthrop Center are better positioned to avoid those costs while also qualifying for favorable green financing terms.
C-PACE has existed in Massachusetts since 2016, but adoption in the state has been limited, according to Bisnow's reporting. That changed somewhat after MassDevelopment and the Massachusetts Department of Energy Resources revised PACE Massachusetts guidelines for new construction in June 2026, streamlining application and approval processes and expanding eligibility for projects. Darien Crimmin, WinnCos' vice president of energy and sustainability, said at a Bisnow event that interest rates on projects he reviewed ran around 8.5%, and that WinnCos has in some cases obtained cheaper financing elsewhere or used reserves instead.
Nationally, the C-PACE market has expanded rapidly. According to PACEnation figures cited by Bisnow, C-PACE lending grew from $2.2 billion in 2020 to $9.72 billion in 2024, while CRE Daily separately reported that commercial C-PACE volume jumped 63% in 2025 alone, to $3.6 billion, with average loan sizes nearly doubling to $39 million as combination C-PACE and private debt structures became more common in major urban markets. Nuveen Green Capital, which closed $75 million in capital commitments back in 2017, closed $1.4 billion in commitments in 2025.
How Winthrop Center Stacks Up Against Other Mega-Deals
The Winthrop Center loan joins a short list of headline-grabbing C-PACE transactions around the country. Post Brothers landed a $465 million C-PACE loan in 2025 for a 525-unit office-to-residential conversion in Washington, D.C., which Bisnow reports was the largest loan originated in C-PACE's 18-year history before this Boston deal. Hoodline's own recent coverage also detailed an $88.4 million C-PACE tranche embedded inside an $867 million overhaul at 111 Wall Street in Manhattan, part of a broader shift toward stacking C-PACE debt alongside private capital in large multi-tranche financing packages.
Massachusetts Governor Maura Healey said PACE Massachusetts leverages private investment to help building occupants lower their energy bills, while MassDevelopment CEO Navjeet Bal called the Winthrop Center deal the largest commercial PACE transaction in New England to date, according to REBusinessOnline. Whether other Boston developers follow Millennium Partners' lead by pursuing Passive House certification specifically to unlock this kind of financing, and how quickly buyers will absorb condo sales against the new assessment structure, remain open questions as the tower's residential market continues to develop.
