Fiberglass windows holding up way better than vinyl after 5 yrs

We switched to fiberglass about six years ago, and honestly, it's been a noticeable improvement over our old vinyl ones. I was mainly looking for better energy efficiency (you know, lower heating bills in winter), but durability has been a nice bonus. No fading or warping here either, even with direct sun exposure on the south side. Seems like fiberglass really does hold up better long-term... at least that's been my experience.

I've had fiberglass windows in for about four years now, and I agree - they've been solid performers. Vinyl wasn't terrible for me, but it did warp slightly on the sunny side. Fiberglass just seems more stable overall... plus, fewer drafts mean fewer sweaters indoors, haha.

The south-side performance mentioned here is where fiberglass has a real advantage: the frames generally move less with temperature changes than vinyl. But I wouldn’t treat the frame material alone as proof of better long-term performance.

Drafts can still come from mediocre installation, poorly adjusted hardware, failed seals, or a glass package that isn’t suited to the exposure. Drainage matters too. A window can have a stable frame and still develop problems if the sill pan, weep paths, or surrounding flashing aren’t handled correctly. For a replacement, I’d pay at least as much attention to the installer’s details and the glazing specification as to fiberglass versus vinyl.