The introduction of green building certifications, on the one hand, can provide useful information for different stakeholders, such as developers and buyers, to evaluate “green” buildings’ environmental performance. On the other hand, it gives rise to an issue resembling the “lemons” problem in New Institutional Economics, as sellers such as developers and owners of properties with poorer ratings do not disclose, or only partially disclose this information to the public. Given that a likely result of this “lemons” problem is lower average market prices that drive good products out of the market, this paper, thus, investigates this latent issue by assessing how the knowledge of these “lemons”, referring to BEAM Plus-assessed buildings with an “Unclassified” rating, influences the price effect of BEAM Plus certification for other certified properties. Utilizing Bayesian Modeling, the findings indicate that should the “green lemons”, or BEAM Plus-assessed properties with an Unclassified rating, be known, the price premium for other BEAM Plus-certified properties on Hong Kong Island and in the New Territories is higher than the scenario under which “green lemons” are not known as thus mistaken as non-assessed properties. This finding is akin to the traditional “lemons” issue which can result in the saturation of “lemons” in the market due to lower average prices that drive the good quality products out of it. This situation, we believe, is further exacerbated by the HKSAR government’s GFA Concession Policy that grants GFA concessions to projects assessed under BEAM Plus regardless of rating, which is reflected by the high percentage of assessed projects with an “unclassified” rating. A higher degree of disclosure for these “lemons” compared to what is required now, according to the findings, could benefit potential investors and the BEAM Society alike.