A bit more about this window restoration project:

Yes, we are restoring the windows with an epoxy repair system.  It is
important that we retain the original glass.  THe glass currently has a UV
film covering.  The museum feels uncomfortable with this solution.  Also,
there are bubbles in the film.  We're going through this whole window
restoration program -- I hate to use the film again, considering that it will
have to eventually removed.

There were storm windows on the building (1893) soon after construction,
although they were not original to the building.  The house was constructed by
a prominent architect -- so the interpretation from both the interior and
exterior are important.

I am interested in the suggestion that the storm panes be on the exterior
rather than interior.  The manufacturer's tend toward interior installations.
I am also tending toward laxan rathern than low-E.  Lexan has up to 98%
UVprotection.  Still working on it, though...

Anne