Glazing specifications for existing building

Hi, I am developing a simulation (EAP2/LEED CS) for an existing building located in Rio de Janeiro. According with the Table G3.1.5, for the Baseline: "Existing Buildings: For existing buildings envelopes, the baseline building design shall reflect existing conditions prior to any revisions that are part of the scope of work being evaluated" Considering that this building it is from the 70´s, it becomes difficult to obtain the glazing specifications through design evidences. I whould like to expose two different cases and how should I proceed: • Clear glazing o Can I measure its thickness “in situ” and consider the corresponding characteristics (eg.U-FS = 5.17 and SHGC=0.83)? • Colored glass or glass with solar control film: o Can I consider the worst case scenario for my simulation and admit a glass with SHGC=0,25 that complies with ASHRAE 90.1 2007 (Table 5.5-2) o or should I perform a test in order to clarify what is the present SHGC? (expensive option). Waiting for your feedback. Best regards