FWIW, I have used the Richards Nisley’s coffee filter test on several fabrics
(to see Richard's post: http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=86001):
- 12-denier rip-stop Ballistic Airlight nylon (Montbell Dynamo wind pants): less breathable than 16 layers of coffee filter paper (I gave up)
- Pertex Quantum (RAB Generator vest): 16 layers of coffee filter paper
- Decathlon proprietary ripstop polyester hard shell wind shirt fabric (http://www.decathlon.co.uk/rail-trail-windproof-mens-jacket-white-black-id_8245773.html): 8 layers of coffee filter paper for main white fabric, 3 layers for black side panels.
- Pertex Equilibrium (RAB Alpine wind shirt): +/- 50% more breathable than 1 layer of coffee filter paper
- RAB Boreas wind shirt: +/- 50% more breathable than 1 layer of coffee filter paper (the Boreas is both stretchy & close fit => in reality breathability is even increased as large sections of the fabric will be stretched when worn).
The difference between hard shell wind shirts and Pertex Equilibrium/Boreas is very significant.
I tested solely using my lungs (thus excluding te use of my tongue and mouth muscles – big difference).
I also compared the DWR of the fabrics, excluding Pertex Quantum: I loosely fitted all fabrics with an elastic on top of a small cup and poured 100ml on top of the fabric (cf. David Chenault’s dwr test in his 2012 State of the Market Report of wind shirts).
- Boreas: wetted out immediately, water filtered through the fabric in less than one minute (*)
- Pertex Equilibrium: after 4h, no drainage whatsoever (note: brand new, unused wind shirt)
- Ballistic Airlight: all water drained through the fabric after 1:40h (thus confirming David Chenault’s assessment in his 2012 State of the Market Report that Montbell needs to work on its DWR (**)).
- Decathlon proprietary ripstop polyester hard shell wind shirt: maybe 20 drops filtered through the fabric after 4h.
(*) Last season, I applied Nikwax DWR wash in – now removed as I have since washed it numerously using regular washing powder – however on the trail without noticeable difference. Not surprisingly as it does not have a hard shell fabric but a stretchy woven fabric.
(**)Last season, I have washed my Montbell wind pants with Nikwax DWR and since then washed it approx. 5x using regular soap. I think my next pair of wind pants will be a Patagonia Houdini.