Your opinion on 6" msv/pbk vents -VS- plastic flappers

Our company has been using positively connected metal flapper vents for bathroom/kitchen exhaust for years. We operate in the Pacific NW. We have recently noticed a few issues with the 6" vents sweating during very cold outside temps. I don’t remember this happening very often at all until recently, maybe just the right weather/humidity? Just want to know how many of you other professionals have switched from plastic to metal, and then back to plastic. We will continue to use rvo-38’s but our future flapper vents will be plastic unless you have a better idea. Thanks in advance.

The problems we have with bath exhaust tend to be the tube freezing because the tube is laid horizontally.

The bath exhaust is frequently exhausting air with a very high water content, this could appear to be condensation.

Run the tubes vertically as much as possible and use insulated tubes if you can find them.

I doubt the issues you are seeing are due to the material the vent is made of.

True…we could always incorporate insulating their tubes in to our bid. Good point