If you are looking at the strict interpretation of GLB, then only CONSUMER information is covered. And CONSUMER information is that information obtained by a Bank in response to a request for a financial product for personal, family, or household purposes.
So it would appear that a transaction for a COMMERCIAL office building would not fall under the Privacy Regs even if it meant sharing information about an individual.
ONE CAVEAT - heaven forbid you would be using a commercial building as collateral for a consumer loan. Don't laugh - I've seen it - A loan secured by an office building to pay for cost overruns in the construction of the building owner's PERSONAL residence. Imagine the shock on the Loan Officer's face when I told him that Reg Z disclosures were needed!
The other part of the GLB states that information can be shared when necessary to complete a transaction initiated by the consumer. If sharing certain tax return information is necessary in order to prepare an appraisal, it seems that would fit under the allowable exception.