I slept out in my bivy in the first big rain of the season. Be sure to get the full story here!
The East Bay Bike Camping group on Facebook snowed over yesterday with a flurry of posts. The discussion was over whether to go with a bivy sack or a lightweight tent for bike-packing. In fact, it wasn’t much of a debate — everyone else seemed to prefer tents over a bivy!
Since I’ve been ultra-light cycle touring the last several weekends with a secondhand bivy sack, I decided to go to bat for my new favorite piece of equipment. One person asked whether there was a bivy out there with:“solid waterproofing that will keep a down bag dry in a small puddle (ha!) and has a mesh for dry buggy nights.”
My bivy is identical to this one by Chinook, who copied it from my North Face bag. It has a mesh (check!) but I had no idea how waterproof it is. Fortunately, the forecast last night was “100% chance of precipitation” — so I took the opportunity to sleep out in the wet.
Findings after Bivy Rain Test #1:
1. The bivy floor was fairly wet in the morning. This might be solved with a Tyvek footprint or fancy silicone impregnated tarp.
2. The sleeping pad was also damp in the lower body area. Some of this may have been wicked up from the bivy floor, but it was mostly because I used the sleeping bag as a sponge (like I said, you’ll have to read the full report).
3. Climbing back into a damp sleeping bag (a.k.a. sponge) was not a big deal. However, I was only comfortable and avoided hypothermia because it was in the mid-50s Fahrenheit last night. Also — I’ll skip the cotton sleep gear next time. Wet t-shirts are for contests, not the bivy!
4. The top of my sleeping bag was a bit damp. The GoreTex can definitely be renewed on the bivy. It’s also a fact of life that GoreTex sticking to my bag is going to wick moisture inwards.
I still think the bivy is ideal for fair weather camping and optimal for short weekend bike-camping trips. I would hesitate to recommend the bivy as rain-season kit for anyone but experienced campers. The problem of soaking through the bottom is about the same as I’ve seen on any previous lightweight backpacking tent I’ve used in the wet, with or without a footprint. However, the problem of soaking through the top is unique to the bivy and definitely a compromise.
As for the other major concerns of the bivy:
1) Sleeps one. (Great! I got the darn thing cuz I got dumped…)
2) Claustrophobic. (Cozy!)
3) No place to stash gear/wet clothes.
This problem is highly dependent on the style of bike-camping. I sleep in all the gear I carry (bedroll, sleep bag, bivy) and have room to stash my fanny pack/feed bag and stuff sack at the head of the bivy. I think I would throw the (wrung-out) wet clothes into a trash bag and leave them outside — they’re not going to dry anyway, whether I’m in a bivy or a tent.
To address the original question:
You won’t get solid waterproofing on anything unless you sleep inside a giant rubber banana — watertight and airtight! Every breathable, spacey material (GoreTex, eVent) that gets soaked through will let moisture in. I plan on trying out the bivy again in a downpour to test the “waterproof” shell on my down bag — that would be the proof of pudding on whether I can extend bivy use into the Bay Area wet season.