EPIC fabric for bivvy bags

[Moondog55]

I just made a purchase on Evilbait, when the package arrived I was very pleasantly surprised to find that what I had bid on was not as described but much better; I thought I was bidding on some coated ripstop, what I got was 10 meters of EPIC treated ripstop instead.
Question is? Is this suitable for a bivvy sac for extreme temperatures, I have not been able to find any information on its breathability at very low temperatures ; say minus 30 and lower.
Also in the mixed package is some very heavy Gtex for a floor and I now have some "Stormliner" Gtex so I won't need to experiment with Tyveck as a shell.

I like making my own gear so today I am a happy camper/climber/bush-walker/skier

[Orion]

For what it's worth, Bibler / Black Diamond used to sell a "winter bivy" made of Epic fabric. Very lightweight; not intended for really wet conditions. BD has since switched to a different fabric, NanoShield. I can't tell you if Epic loses breathability in extreme cold, but I have read something to the effect that moisture can freeze within the fabric itself. Frankly, it's likely a problem with most fabrics in the cold: frozen condensation limiting breathability. My breathable single wall tents (Epic, Toddtex, and one other fabric I forget the name) all frost up pretty good at times. A bivy sack will just be worse.

[Moondog55]

As its main function is to protect the fragile sleeping bag fabric from dirt it should be OK then, I have used my MD "Foxhole" down at minus 18 with no problem so I should be fine

[Franco]

I have read some comments on this but cannot remember the exact details. From memory there is a gap around -5 to about -20c where it does not work well.
I see if I can find some info for you...
Franco

[Moondog55]

Thanx Franco, if it does work below -20 fine, my wife wants it for a raincoat; I get what's left