On Sunday, March 15, 2015 at 5:25:43 PM UTC-4, Mayayana wrote:

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You can replace the whole window. I don't know
what you mean by storm window.

From IDK when up until the ~60s, storm windows
were the outter windows. You had double hung wood windows,
and outside wood storm windows that were put up in
fall. Come spring, the windows were taken down,
wood framed screens put up that fit the same opening.

After the 60s the trend was to aluminum windows that had
window and screens combined, they stayed there permanently,
you could slide them up/down and choose either a window or a
screen for the lower half. You slid the window up, the screen
down, or vice-versa.






To me that means
an aluminum frame with two panes and a screen that
gets screwed to the exterior casing. But if you mean
to use a new window it will have its own sill. The trouble
there is that you'll need to remove and redo both the
inside and outside trim.