Did a bunch of these last winter in an old Craftsman. Once the inserts were in, drafts dropped off a ton—honestly, no real cold spots unless you stood right up next to the glass on a windy day. The only spot I noticed condensation was along the bottom edge, but nothing major. I skipped extra weatherstripping at first, but after a couple weeks I added a thin foam strip on one window that had a stubborn gap. Sometimes you don’t know till you live with it for a bit. Sounds like you’re on the right track.
That sounds really familiar—I had almost the exact same thing happen with a couple of my old double-hungs. After putting in the inserts, it was like night and day for drafts. I was honestly surprised by how much warmer the rooms felt, especially since I’d been skeptical about how much difference they’d actually make.
Did you notice any noise reduction too? For me, street noise dropped off a bit, which was a nice bonus. The condensation along the bottom edge is interesting... I got a little of that too but only when it was super cold outside. Never turned into anything more than a bit of fogging.
I held off on extra weatherstripping at first as well, thinking maybe I could get away without it. Ended up adding some on two windows after a few weeks—just like you said, sometimes you don’t spot every gap until you’ve lived with it for a while.
It’s always a bit of trial and error with these old houses, but it sounds like you’re making all the right calls. Curious if you ran into any surprises during install?