Chris Perdue wrote:

you will get very little benefit from the storm windows in the form of R
value...

Au contraire, you'll get another US R1, or perhaps more, with low-e.

some wind resistance, but that is not a problem with new weather
stripping and sashes, especially double paned glass...

Double-pane R2 becomes R3, a 50% improvement.

...heat build up *is* a major concern ,even in the winter time...heat from
direct sunlight can build up between the storm sashes and your window sashes
very quickly even in the winter time...the vinyl jambliners are prone to
warp at about 150-160 degrees (F)(as are vinyl windows)...

If 250 Btu/h-ft^2 (full sun) were to hit the storm window (unlikely, given
the angles involved) on a 30 F day and the window passed 225 and the screen
absorbed 20% of that, ie 45 Btu/ft^2, and that heat moved to the outdoors
via an R1 storm with no air leaks and to 70 F indoor air via an R2 window,
the net heatflow out of the storm window would be (70+45xR0.5-30)/(R1+R0.5)
= 42 Btu/h-ft^2, so the temperature near the screen would be 30+42xR1 = 72 F.

Nick