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...
The stuff expands more than you expect, and trimming the excess can get messy if you’re not careful.
That’s the part that always gets me. I’ve done a few window installs where I thought I was being conservative with the foam, but it still mushroomed out around the frame. I’ve found using a straw applicator helps control it a bit, but I still end up with some cleanup. One thing I started doing is waiting for it to fully cure before trimming—if you try to cut it too soon, it just tears and makes an even bigger mess.
Did you notice any shifting or bowing of the window frame from the foam pressure? I had one older sash that went slightly out of square after I overfilled the gap. Since then, I’ve been careful to brace the window until the foam sets. Not sure if that’s overkill, but it’s saved me some headaches.
Curious if you tried any of the newer foams that claim “no bowing” or “minimal expansion”? I haven’t had a chance to test those yet, but I’d love to hear if they actually make the job easier...
I’ve had the bowing issue too, especially with older wood frames. One time I got a little too enthusiastic with the foam and ended up fighting to get the window to latch right. I haven’t tried those low-expansion foams yet—honestly, I’m a bit skeptical. The regular stuff already costs enough, and I’m not convinced the “minimal expansion” claims are more than marketing. Bracing the window while the foam sets seems like a smart move, though. It’s a little extra work but worth it if you’re dealing with anything less than a rock-solid frame.
I’ve wondered the same thing about low-expansion foam—seems like every can says it’s “minimal” but who knows what that really means. I did a test with some regular stuff on a scrap frame and it pushed the jamb out just enough to mess with the reveal. Bracing helped, but it’s a pain if you’re working solo. Has anyone actually measured how much those low-expansion foams expand compared to the regular ones? I’m tempted to try it, but not if it’s just hype.
I totally get what you mean about the “minimal” label—feels like a guessing game sometimes. When I did my bathroom window, I used low-expansion because I was paranoid about messing up the reveal. It still puffed out more than I expected, but nowhere near as bad as the regular stuff. I didn’t measure it, but it seemed like maybe half as much? Still had to brace, though. Honestly, it’s not just hype, but it’s not magic either.
I actually had the opposite experience with the “minimal” stuff. Maybe I got a dud can, but it barely expanded at all—like, I thought I messed it up somehow. Ended up having to go back and fill a couple gaps with caulk because there were these random air pockets. Guess it depends on the brand or maybe I just got unlucky. Either way, I kinda miss the drama of the regular foam... at least you know it’s working.
Yeah, I’ve had that happen too—one can foams up like a marshmallow in the microwave, next one barely puffs at all. I kinda wonder if temp or humidity messes with it? The regular stuff is messy but at least you know when it’s overkill... and when it’s not.
- Honestly, I’ve had cans that expand like crazy and others that just kinda... fizzle.
- I always thought maybe I shook one more than the other, but now you’ve got me wondering if it’s just the weather.
- The mess is real—once had foam ooze out and stick to my cat’s tail, which was a whole adventure.
- Anyone try storing the cans at different temps before using? Does that actually make a difference?
I’ve definitely noticed the expanding foam acts differently depending on the temp in my garage. If it’s cold, it barely comes out, but if I leave a can near the water heater, it’s way more lively—sometimes too much. I’m also wondering if humidity plays a role? My basement gets pretty damp and I swear the foam sets up faster down there. Anyone else seen that, or am I just imagining things?