Tyvek vs Similar Materials for MYOG Bivy

I’m not sure how much price and weight mean to you, and you might already be aware, but most of the commercially made Tyvek bivys such as Montbell are made with the lighter 1.25 oz per sq yd Tyvek and not the heavier 1.87 oz Homewrap. The lighter 1443R also breathes better, and is nearly as water resistant as the Homewrap. In the drier Arizona climate where long drenching rains aren’t likely, the lighter Tyvek won’t wet out. Questoutfitters carries it.

https://www.questoutfitters.com/uncoated_fabrics.htm#TYVEK

And here is the one Montbell offers.

https://www.montbell.us/products/disp.php?cat_id=14007&p_id=1121323

Thanks Monte – I did not know that. In doing research on MYOG bivys I’ve seen Montbell come up a few times.  I can’t seem to get the website to load on may of my devices so I didn’t know if they were just having technical issues, defunct, or what the issue is.

But really good information about the 1443R, I only saw one blog on it and that person thought there was too much condensation with the 1443R but I really appreciate more input on that. I thought that fabric would have been a better option and it’s nice to know I’m not crazy!

Bethany, which blog thought a Tyvek 1443R bivy had too much condensation?

Section Hiker thought this Tyvek 1443 bag cover did well: https://sectionhiker.com/tyvek-sleeping-bagquilt-cover-from-terra-rosa-gear/

And this blog has a MYOG bivy out of Tyvek 1443R that also seemed to do well: http://unfinished-tales.org/2016/12/23/field-testing-tyvek-1443r/

It must be your device(s) that’s the problem of not being able to bring up the Montbell link because I’m having no issues from my Windows 10 PC. Maybe try the Montbell Euro link. You of course wouldn’t want to order from Europe, but you can at least get a look and check out the specs of the MB Tyvek bivy.

https://euro.montbell.com/products/disp.php?cat_id=14007&p_id=1121323

ulog in the UK also carries the MB Tyvek bivy and they have an “Our Verdict” that you can click onto to get their opinion of different products. Perhaps you can pull up their link.

https://www.ultralightoutdoorgear.co.uk/equipment-c3/sleeping-bags-c21/accessories-c121/montbell-tyvek-sleeping-bag-cover-p14100

John – I’d really have to dig to find that blog again. It was just one I found online with no remarkable credibly one way or another. Thank you for those other links – they are very helpful.

Monte – Yep – the links worked fine on my husbands computer. Very odd but thanks for helping me figure it out!

I once made and used a tyvek home wrap bag inside my sleeping bag for 1/2 of one night, inside 2 layer tent with outside temps around freezing..

Not exactly what you are describing but the info might be of use to you in some way. .  I think I was experimenting with moisture barriers at the time.

Felt damp and cool for the first half of the night. By the  middle of the night I was in a pool of water (sweat) trapped by the inner bag.  Had to remove inner bag, change out of wet clothes and start over.  Very chilling experience.

I tend to sweat more than most people.   Your mileage may differ.