Hello all....
I would suggest building exterior wooden storms, glazed with a low-E glass.
Chances are good that originally there were storms built for the exterior, but
then again....most of my experience is residential, and perhaps the exterior
casings are not kind to that sort of solution.  If indeed there are old
storms..they are probably stashed in a basement.....up in the joists......some
utility closet.  The old maintenance man died 40 years ago......lost the
keys......no one knows WHAT those window-looking thingies are.....
Two schools of thought on fennestration:
   1:....double pane glazing should be vapor-proof..(to keep them from
fogging).
   2.....double pane glazing should be permeable to vapors (to keep them from
fogging)
Perhaps....I am thinking.....it is best to use wood storms over wood sashes,
and use a metal storm over metal sashes.  ....But indeed.....DO NOT cover the
interior of the primary sash!  Go to the outside.  If a window must breath,
allow it to.  Wood must breath.....allow it to, and plan on its movement.
Henry  Roeters