Old house with new construction window

Should the vinyl replacement window have fins?

That is a very open-ended question, and the answer could vary depending on the circumstances. Generally speaking, a window can be installed with OR without fins in an older home. Whether or not it should have fins depends on the type of installation and other factors surrounding the home.

In a new construction application..yes.

Insert...no.

What helpful information would assist in assessing the "should" aspect of this question.
Home built around 1900. Old windows removed in a kitchen remodel. New wall built from floor to ceiling with framing for new window in one case. The other window opening was
enlarged using one side of old framing and new framing on other side. Vinyl siding outside.
Thanks for opinions/insights/experience.

Either will perform jsut as well as another if done properly.
More important is the energy performance of the windows.
So concentrate on the U, SHGC, AI, and DP.
TheWindowNerd....

+1

If done properly, it won't leak.

Nailing flange is probably easiest but it may not have been available in his application with his size.

Can fins be added after the replacement has been set, caulked and sealed?

No.

Flashings, via drip caps and wrapping...yes.