I’ve actually had the opposite experience with attic temps—didn’t notice a real difference between metal and plastic vents, at least in my place (asphalt shingles, moderate pitch, Midwest weather). The airflow seemed about the same. For me, it was all about how well everything was sealed and flashed. I get what you mean about condensation under the flange on metal ones though—had to redo some caulking after a rough winter. Honestly, I think proper install matters more than vent material for performance. Longevity-wise, metal wins, but as far as airflow goes, I’m not convinced the material itself changes much.
That lines up with what I’ve seen, honestly. I’ve swapped out both metal and plastic vents over the years (asphalt shingles, northern Illinois), and I can’t say I ever noticed a real airflow difference either. Like you said, it’s always been about the install—especially making sure the flashing is tight and there aren’t any weird gaps for water to sneak through. The one time I had condensation issues, it was a metal vent that wasn’t sealed right after a big freeze/thaw cycle. Had to get up there with a tube of caulk in March... not my favorite Saturday.
I do lean toward metal for longevity, just because the plastic ones seem to get brittle after a decade or so with our temperature swings. But as far as attic temps or moisture control? Haven’t seen much difference. Curious if anyone’s actually measured airflow rates between the two, but in practice, it seems like the bigger deal is just making sure everything’s buttoned up tight.
I get where you’re coming from, but I’ve actually seen some measurable airflow differences with certain vent designs—especially when you get into the low-profile plastic ones versus the old-school metal box vents. It’s not always dramatic, but on a couple of green roof retrofits we did, the plastic models just didn’t move air as well in the summer. Could be the way the louvers are molded or maybe just the opening size. I’m with you on install being critical, though—bad flashing or a sloppy cut negates any material advantage. Still, I’d be curious if anyone’s compared ridge vent performance across materials, not just box or turtle vents.
That’s a good point about the plastic vents—I've noticed similar results, especially on some of the older buildings I manage. The airflow just isn’t quite the same, and I’ve wondered if it’s a combo of the vent design and the way the attic space is laid out. I’m with you on install being a dealbreaker, though. Even the best vent won’t help if it’s not flashed right or the opening is undersized. Haven’t seen much side-by-side on ridge vents by material either, but now I’m curious too...
I get where you’re coming from about the plastic vents, but honestly, I’ve had the opposite experience at my place. I swapped out some old metal ones for plastic a couple years back (midwest winters, lots of snow and ice), and the airflow actually improved. Maybe it’s just the brand or how they were installed, but I noticed less condensation in the attic after the switch.
I do agree that install is everything—if the opening’s too small or they’re not sealed up right, it doesn’t matter what material you use. But I’m not totally convinced that plastic is always worse for airflow. Metal can get banged up or rust over time, especially if you’re dealing with a lot of freeze/thaw cycles.
I guess it really depends on your climate and how much maintenance you want to deal with. For me, the plastic ones have held up better than I expected... but I’m sure there are situations where metal makes more sense. Just my two cents.
