Does anyone have any rules of thumb on a quick/easy approximation for
taking a Center-of-Glass U-value and converting it to an Assembly
U-value based on industry standard assembly constructions? I know this
depends on a lot of variables, like frame material and conductance, and
the size of the overall glass assembly, etc., but I'm just looking for a
quick estimate on performance reduction for comparisons to other window
types for a particular building.

Also, is there an ASHRAE 90.1-2004 Baseline glass Visible Light
Transmittance (VLT)?

Josh Greenfield, PE, LEED AP