New Integral Designs Penguin Reflexion Bivy

the fabric looks pretty nice if it works, but I'm worried about putting the zipper on top of the bag. Of course it is designed for winter and high altitude mountaineering, but that seems to pointlessly limit the design to uses below freezing. Is there any performance advantage to having the zipper on top? Is it so you can open the zipper for a face opening?

"Is there any performance advantage to having the zipper on top? Is it so you can open the zipper for a face opening?"

The performance advantage that I see is that you can sit up easier while still halfway in the bivy. I made a bug bivy this summer that has a central zipper and I find it much more useable than if the zipper were horizontal across my face.
It seems that the gentleman in the picture has the zipper open for a face opening. The problem I see is that if someone wanted to sleep on their side, they'd be breathing into the fabric, not into a direct vent.

Why would a zipper on top design limit the usefulness of the bivy?

I would need to see some breathability comparisons. I'm skeptical for now. Probably most beneficial in very cold conditions.

Top center zipper is very handy for venting, contortion-free entry, and sitting up with feet still in the bivy. It's bad for entry during wet weather unless under a tarp.

Watch BackpackGearTest.org for test reports in the coming months. The concept is intriguing, so I'll be very interested to see how it performs, especially with respect to breathability.