Honestly, nothing beats a solid bead of caulk for those weird little gaps...
Couldn’t agree more about the caulk. I’ve seen way too many folks try to skip that step, thinking the magnets or weatherstripping would do all the work. It’s always those tiny gaps that end up letting in the draft.
I actually tried the magnetic kits on my own place (1940s double-hungs), and prep was everything. If there was even a bit of old paint or dust, the magnets just wouldn’t stick right. For bigger windows, I ended up running a thin strip of clear acrylic along the bottom edge to help stop the flexing—looked decent and held up in a storm, but it’s a bit of a hack.
One thing I’ll say for the magnetic kits: they’re a lot less of a pain to remove in spring than shrink film. No sticky residue, no peeling tape. But yeah, if you’re in a windy spot, you really have to overdo the magnets or they’ll pop off. Worth it for the look, but not a total fix if your frames are super warped.
Funny, I thought I could get away with just piling on more weatherstripping one winter—lesson learned. The drafts found their way in anyway, right where the sash meets the frame. Ended up crawling around with a tube of caulk and a flashlight like some kind of home improvement detective. Still think nothing beats caulk for those sneaky gaps, but I do like the magnetic kits for the easy removal. If your windows are as crooked as mine, though, it’s a constant battle...