I always feel like you still need a good bead of caulk on top or air sneaks through.
That’s exactly what I was wondering! We just moved in last fall, and our windows are ancient. I tried the backer rod plus caulk combo for one especially drafty spot, and honestly, I noticed less cold air coming in after. But yeah, if it’s just the foam, it does seem a little too squishy. Has anyone tried those “low expansion” spray foams instead? Wondering if they hold up better over time or just make a mess...
I totally get where you’re coming from—those old windows are a pain. When I first tried the low expansion foam, it honestly did a better job sealing than just caulk or backer rod alone, but it was super easy to overdo it. The stuff expands more than you expect, and trimming the excess can get messy if you’re not careful. Still, once it cured, the drafts were gone and it held up fine over winter. Just have a steady hand and maybe some patience for cleanup...