Kenneth wrote:
....
Consider the analogy (though far more extreme) to a clothes
drier:
....
It seems to me that over time (and let's remember that the
volume of air in the window is extremely low) both the RH,
and the absolute humidity of the air in the window would
drop.

Then, when the epoxy seals the hole (while the window is
still warm) the AH within would be lower than the
surrounding environment thus lowering the temperature at
which condensation would be visible.
....
Not unless the replacement air is drier than the air which one is trying
to displace -- which it isn't since it would be only some very small
fraction of air displaced by the volume expansion of a minimal amount of
(localized) heating.

The only way to make any significant difference would be the same way
the window was manufactured--draw a vacuum and fill w/ dry gas which
ain't gonna' happen.

Only real choice is to get the window repaired/replaced.

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