Any experiences with felt on underside of purlin/metal roof for condensation?

[NathanS]

For an extra $1 a linear foot I could get a felt membrane that is supposed to control condensation and prevent it from dripping from the underside of metal panels that are on purlins. I am curious if anyone has seen this stuff in action.

https://www.abcmetalroofing.com/Residential/Imperial-Rib-/

The alternative would be to sheath the roof with 1x Hemlock and cover it with tar paper. Which, costs about ~$300-350 more. (Cost of 1x + tar paper ~ $700 vs ~$400 for the felt)

The advantage really just seems to be how much quicker it would be to install the roofing on what amounts to a big ladder that spans the width of the building. If the felt didn't work it would be a nightmare. We go below the dew point virtually every night during the growing season.

[Don_P]

The felt works here. I've seen the dripstop metal advertised for several years but no experience with it.

[akwoodchuck]

Did a metal roof over purlins on a cabin years ago,, we ran vertical courses of felt with interlocking folded edges to keep it from drooping...seemed to work well. Redid a 1940s built-up roof last summer, when we tore the last layer of tar paper off, the 1 inch spruce planking still looked brand new...that was good stuff!