I have received a few private messages recently asking about soft shell fabrics. Since I feel that this information is probably of general interest I am responding in a forum post.

Softshell fabrics can be best categorized by their porosity in cubic feet per minute (CFM):

Polartec Windbloc 0 CFM… PU layer
Gore Windstopper <2 CFM Porous Teflon membrane without the Gore PU layer
eVENT <2 CFM Porous Teflon Membrane (hard shell product for ref only)
Driclime windshirt 3 – 5 CFM
Patagonia Houdini windshirt 5 CFM

Average human can detect forced convection (wind) above 5 CFM

Polartec Powershield 8 – 16 CFM Perforated Membrane
Polartec Windpro 60 CFM
200 wt Fleece 200 CFM

Richard,

Thanks for that. I didn't know if my PM got through.

I'm confused by the Powershield numbers. I didn't realize that the whole Powershield line had a perforated membrane, but upon review of their website they show the exact same image for each with the perforations. Do you know the difference between "Powershield" and "Powershield 02"? Is it just that one uses the "velour" and the other "microvelour" backing?

EDIT: I've seen older references to "Powershield Light"- I'm wondering if this is now called "Powershield 02" and is simply the thinner backing. See posts by Mark Verber and Ryan Jordan in this thread
Soft Shell Advice: on 10/12/2005

Edited by jimqpublic on 12/11/2009 12:31:14 MST.

Jim,

The Powershield number I quoted was for the most popular variant. I am not familiar with all the others.

Edited by richard295 on 12/12/2009 11:22:59 MST.

Thanks for these numbers Richard. It reminded me of an earlier posting by you on Air Permeability Info. Any others numbers would be appreciated.

Numbers I have seen but haven't verified.

patagonia Ascensionist 5cfm
arcteryx squarmish 7cfm
equilibrium 10cfm

Guestimations... real numbers would be appreciated:

scholler dynamic ~25cfm?
scholler dryskin extreme ~30cfm?

--Mark

Edited by verber on 12/11/2009 15:53:52 MST.

I can say, subjectively, that I don't feel any wind through my Patagonia Ascensionist, whereas I did through I couple of membrane fleeces that I tried and didn't like before.

I love my Ascensionist. I view it as a contemporary equivalent of the old canvas or ventile anoraks - although less of a catastrophe if it gets wet. Or as a kind of heavy duty winter windshirt: with a base layer or two under it, I find I'm fine for pretty much anything as long as I'm moving, and when I'm not moving so much I have room under my size Large (at 6' and 180lbs) for a fleece or a down sweater if I need one.

It's definitely not a garment to carry: I only bring it if I expect to be wearing it most of the time.

Thanks Richard for bringing the science, it's nice to have a counterpoint to anecdotal experience.

Having owned and used both a Houdini and a Ready Mix (now Ascentionist), I find it hard to believe that they're equally air permeable. For chilly and windy BC skiing last winter I took to wearing my Traverse pullover over my Houdini, which gave enough wind resistance for all but all-out alpine storms. The Ready Mix by itself seemed more wind resistant.

Then again, separating wind resistance from warmth might be difficult when using only personal experience.

Windbloc has a non-perforated PU laminate between two fleece layers.

Any idea how much vapor permeability there is? I'm wondering if this material would make good vapor barrier socks similar to the RBH designs VaprThrm insulated socks.

I'm still working on equipping my kids for winter activity and it seems that Winbloc socks might keep their boots dry.

Edited by jimqpublic on 12/18/2009 18:50:58 MST.

I have never felt the wind through my Arcteryx Gamma SV (powershield) and I have taken it through some rough wind. My Patagonia Houdini lets anything more than a light breeze though.

Maybe Arc sourced a stouter variant of powershield.

Blast from the past, but Richard, do you know how CFMs combine together? For example, if I have a 15 CFM softshell garment, and add a 60 CFM Windpro fleece garment, what would be the total CFM? What about if I have a 5 CFM windshirt (for each combo)?

Thanks!

Brian,

The simple way to calculate your combined CFM is:



AP11 – AP1N are the air permeability values of the individual layers.