Joe Valesko recently sent me an email, which said in part "Would you be interested in testing our Ventum nylon fabric to see how it compares in breathability to Pertex GL? It feels about the same to me, but that is hardly scientific."
My testing results are as follows:
Pertex GL RS from ZPacks 2015 version micrograph at 1.4mm FOV
Pertex GL RS from TNF Verto 2011 version micrograph at 1.4mm FOV
Ventum RS from ZPacks 2015 version micrograph at 1.4mm FOV
The Pertex GL spec is still listed at http://www.pertex.com/product/quantum-gl/ as <1 CC. The equivalent imperial value is <1.9685 CFM. After Joe Valesko read this post, he said in part, "For your reference, Pertex makes a variety of fabrics under the Pertex GL and Pertex Quantum names. "GL" simple refers to the weight range, but my understanding is there are multiple GL fabrics with different weaves, surface textures, etc. Yes that makes it pretty confusing. That could be why your previous test from 2011 was different."
