Investigation of the Greenium in Commercial Mortgage-Backed Securities

Research paper by Sena Kahveci and Z. Nuray Guner (2026) | Underwriting, Financing, Capital Stack

Curators: Asha Lad and Bill Bateman

London, UK

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Why we recommend it: This paper believes it is a first-of-its-kind academic study, providing the first empirical evidence of ‘green pricing’ dynamics within the commercial mortgage-backed securities (CMBS) market. While sustainable finance literature has extensively explored uniform instruments like corporate green bonds, this research examines the structured real estate debt ecosystem.

Unlike corporate bonds, which can be issued instantly based on future corporate sustainability promises, a CMBS is a pooled instrument. It requires lenders to first originate a vast number of individual, energy-efficient commercial mortgages, aggregate them over time, and achieve a scale where securitization becomes cost-effective. Crucially, however, this volume has been concentrated within Fannie Mae, a Government-Sponsored Enterprise (GSE), demonstrating the instruments’ pricing potential in the green debt market.

Consequently, the dataset provides a unique window into how a GSE leverages its institutional capacity to pave the way for expanding the secondary market for green debt. Furthermore, this report provides valuable context regarding the ongoing professionalization of sustainable finance. As a market matures, it typically transitions away from loose internal definitions toward rigid, industry-wide benchmarks. By examining how the market responded when artificial agency supports were altered, this study captures a structural shift where participants began leaning heavily on formalized, third-party verification to manage risk. For online readers and industry practitioners, this text offers an objective, data-driven look at how public institutions catalyze and structure new green financial instruments.

Key takeaways:

- Empirical proof of a dual debt-market greenium. The study analyzes a final sample of 12,411 Fannie Mae CMBS issued between 2017 and 2023. It concludes that a “greenium” (a pricing premium resulting in lower yields) exists simultaneously in both the note rates of primary commercial mortgages and the pass-through rates of secondary CMBS.

- Divergent market perceptions of green signals. The findings indicate that different market participants interpret green attributes differently. Primary mortgage originators do not offer additional interest rate discounts for third-party certifications, viewing agency vetting as a sufficient green signal. Conversely, secondary CMBS investors place an explicit premium on independent third-party verification to hedge against perceived greenwashing risks, which significantly drives down pass-through rates.

- Quantifiable yield differentials. By isolating pricing differences from observable property and loan characteristics, the study identifies a distinct greenium. The data reveals an unexplained pricing premium of 11.18 basis points for mortgage note rates and 6.16 basis points for CMBS pass-through rates.

- Regulatory shifts as a catalyst for market adaptation. Following a landmark September 2019 policy change by the Federal Housing Finance Agency (FHFA)—which raised loan caps but removed preferential “carveouts” for green MBS—market behaviour shifted abruptly. Green mortgages holding third-party certifications skyrocketed from a mere 1.89% before the policy change to 30.17% afterward.

- Independent validation replaces policy incentives. The post-2019 data illustrates that when systematic regulatory advantages disappeared, issuers adapted. Independent third-party certification transformed from an optional luxury into a vital risk-mitigation tool used to signal authentic sustainability to increasingly selective investors.

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