If 8 or 9 have already gone, it is likely that the rest are not far behind. Some times you will see accelerated seal failure on elevations that take a beating from the sun. If that is the case here, the others may live a while. Replacing the glass with a sealed IGU with Low-e is likely going to cost as much as an entirely new insert. Insert window utilizes the existing frame and sets the new window inside that frame. Primary drawback is the loss of glass when compared to a full tear out. Full tear out installation replaces everything right down to the studs and all interior trim. Primary drawback, expense.

There is no evidence of wood rot or water damage beyond the exterior trim, and maybe framing. To tell you the truth I'm not sure that I know the difference between "trim" and "frame". But, we have had it all inspected, and so far the damage is limited to the wood around the windows and not (yet) in the interior of the walls. We've got to jump on the repairs, though. Not sure who made the windows. All the actual windows of the house seem very good --- well constructed, very tight, very energy efficient. I guess I could ask some of the original owner neighbors what brand the windows are. Everyone in the neighborhood has exterior wood rot problems, and all are in process of repairing theirs, too. Our one Palladian window that is under discussion is unique to our house --- we are the only one with this "bonus room" in our floor plan. We are also the only ones in the neighborhood right next to the woods.... this window faces the woods, and it is also facing north.

Your best bet would probably be to contact the manufacturer directly.

Says Allenco on hardware, WOW. We're just outside Memphis so pretty moderate climate-wise. It gets cold here but usually not bitterly cold for more than a day or two so not a huge deal there. I'm curious why the choices now are mostly vinyl, fiberglass, or wood. Was aluminum popular/cheap 25 years ago? Several houses in this subdivision have these but these are strictly "builder grade cheapest materials you can find" -type houses. i dont think anyone paid extra to upgrade to alumimim windows.