The multi wall polycarbonate works well for odd shaped windows that are difficult to fit with the usual thermal shades. The polycarbonate can be easily cut to any shape, and is light enough to go up and down easily.
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The upper windows in the left picture have triple wall polycarbonate glazing. The large one is 8 ft high by 5 ft wide, but the polycarbonate panel is still easy to handle. The window in the right picture also has triple wall polycarbonate. It is probably 15 ft off the floor, so the light weight is helpful. Both windows would be difficult to do with other window insulation techniques.
I used the Insulation Upgrade Calculator to estimate the fuel saving and greenhouse gas reduction.
Strom window area added = 130
Old R value = 1.8 (double
New R value = 1.8 + 2.5 = 4.3
(window + triple wall polycarbonate
Fuel is propane at $2 per gallon
Plugging these numbers in the the calculator gives a yearly saving of $220, a ten year saving of $3490, and a yearly saving in CO2 emissions of 1420 lbs.
Here is the screen shot for the calculator:
Revised Oct 6, 2007