Ultralight Bivy Materials

Send a note to Richard Nisley on BPL and I bet you’ll get the information your are seeking.

Michael,

If memory serves (and please correct me if I’m wrong), Borah used to offer their bivy in both M50 and M90, with M50 being roughly .4oz per square yard lighter than M90.  If you search on the forums, there were some reports that the M50 was condensation prone and that M90 performed much better.  Later on, Borah switched to Argon and it was reported, or at least advertised to breathe much better than M50 but weigh about the same.  That’s about when I stopped following the reports on it and I’m unsure if Argon delivered the goods or not.

Ian pretty much has it down. M50 is excellent at repelling water splatter, but has very low breathability. Hence, the reports of condensation inside the bivies. Argon 67/90, M90 or Membrane10 are better bivy fabrics IMO.

Ryan

Thanks for the info. I sent Richard a PM so hopefully that will be helpful. I had seen the posts about M50 not being breathable enough. I found a couple instances where people had cut a venting slit down the top of the bivy to reduce condensation. In terms of the MLD bivy I have gathered people all seem to really like it. I was just wondering if their material is any more superior to the Borah materials, or if it is the craftsmanship/name that drives the price up.

In case you haven’t read these articles before they a worth a look

.STAYING DRY IN A BIVY SACK: TECHNIQUES FOR MANAGING THE MOISTURE BALANCE BETWEEN EXTERNAL PRECIPITATION AND INTERNAL CONDENSATION.

. NIGHT TIME CONDENSATION ON TARP AND TENT FABRICS.

.Dew, Frost, Condensation, and Radiation.

The Bivy Condensation Conundrum.

.BEST WATER-RESISTANT, BREATHABLE BIVY TOP MATERIAL?.

RON BELL.