bivy sack = not fun

Depending on your clothing and bag, I don't think ANY inflatable pad alone would have been enough. You make it sound like you have used the same system in colder weather. Thus, it seems not being on the ground that should have been 10 F warmer was the real issue as someone else pointed out.

The past 3 days I've been testing out my winter sleep system, which is essentially the same as my summer one except I wear more clothes and add CCF foam. I used a NeoAir on a concrete floor with 3/8 (actually measures 7/16) blue CCF on top last night with an REI Sub Kilo 20 F bag. It got down to -2 F and I was perfectly fine. Granted I had no wind in my doorless garage. I'm a total noob at this but from my limited experience it CAN be done.

"not the 20F you have when on a platform in 20F air temps. " J Colten

Sleeping on top of that bench/platform in the shelter may have reduced the r value that was under your body — similar to hammock camping. That is why hammock campers use underquilts. You might be better off sleeping on the ground in a situation like that.

in retrospect nearly nine months later, i would have faired much better if i had stayed near the spring for the shelter. it is located in a small hollow and it was well protected from the wind.

this winter i'll be back out with just the bivy, but i've returned the AirCore and will be using the ridgerest and self inflating combo again.

I think I would have been bedding down behind the shelter rather than in it. I've done this many times behind huts with good success in gale force winds. I've been in situations where the wind was so strong and turbulent that, if fully exposed, the wind actually compressed my insulation significantly making it impossible to stay warm.

I can relate to your experience, never been in the exact same spot, but every time I've chosen a bad camp site seems to be when I make my selection based on a view or the location of a cabin.

I wonder if it would have worked to flip the bivy over so that the bottom was on top of you. My equinox bivy has a larger bottom than the top, sort of a hood. I might have tried flipping it over and seeing if having the hood over my head would prevent wind from blowing the air out. Then I probably would have flipped myself on to my stomach and waited for morning.

It sucks when your camp is bad. I've learned that no matter how sleepless the night is, I usually sleep some of the time and I may not have gotten enough sleep, but I usually get enough rest to continue on the next day.

The reason for your cold night is obvious: The windows in that shelter must be the drafty old single-pane type. Modern insulated windows would have made a huge difference.

Memo to shelter architects: When you remove an entire wall, you pretty much remove the need for windows.

Seriously, it's counter-intuitive to forgo a "shelter" in bad weather, but the bivy-in-the-bushes-next-time argument wins out here. It's funny: That's exactly what you would have done instinctively had there not been a shelter to tempt you.

the shelter is there to protect you, right? i'll let the maintainers know they need to bump up to double pane and to have them turn the shelter so the missing wall doesn't face the direction the wind is coming from :)

thanks Dan, that made me smile.