George said:

Well, you want "replacement" windows, that's for sure. they don't have the
nailing flanges that originals have. Reframing for larger is going to be
costly, because you have to adjust your cripples and headers, maybe even
your siding to make larger openings.

Replacements aren't that bad for a guy with a reciprocating saw and some
help shimming. You can get full vinyl double hung with tip-in washing and
double glass for a lot less than you think. Use that expanding poly-U
"Great Stuff" to stop intrusion, helped by some tape or membrane.

PLEASE don't use the standard Great Stuff in a red can - it will bow
the window frames - guaranteed! Get the stuff designated for windows
and doors.

FWIW,


Greg G.