[nopro]

have old home with iron casement windows with single pane glass otherwise in pretty good shape-need to replace couple hundred panes with double pane-are they available in small sizes as 8x10 and is this feasible?

 

[joecaption]

Not a great way to do it, even with the double pane glass you still have steel frames that are transfuring heat and cold right into the room.
Got any pictures inside and out?

 

[HomeSealed]

Probably not possible, and as joe mentioned, probably not advisable even if it was. Get some good interior storms (since they are casement units) if you want to improve your efficiency without replacement... Pics would definitely help to confirm recommendations...