I have 3 bivvies that pretty much span the gammut of bivy bags:
Least expensive: Camo bivy from The Sportsman's Guide (Guide Gear brand) - This bivy cost under $30. The material is the same on the top and bottom, and is a lightweight coated nylon ripstop. It has a zipper on the right side, and a bug-proof mesh face net. Around the net is a thin wire sewn inside the edge of the body of the bag. The wire allows you to shape the net around the opening so it doesn't lay on your face.
This bivy is quite tight. It rolls however the bag rolls. The zipper is short and entry and exit are a little awkward. A plus to this bag is that I believe it is somewhat breathable, as I have not experienced any condensation inside. I have not used this bag out in the elements by itself. I have used it with a summer weight bag under a tarp shelter when temps dipped below the comfort range of the bag. It works ok, but as mentioned, it is constrictive and awkward to enter/exit. Bottom line: It was worth $30.
Middle-expensive: REI Minimalist Bivy - I purchased this bivy in March during REI's 20% Member sale, and I have only used it once so far. This unit has a coated nylon (I think) grey bottom and a red ripstop nylon top that has the REI Elements laminate as a waterproof/breathable layer. This bag is constructed well. It has 3 sets of zippers, and the zippers go half-way down each side of the bivy. This makes placing your bag inside and getting in and out very easy. Also, you can be inside the bivy, sit up, and arrange the zippers so you can just stick your arms out. It is a very versatile design.
I used this bivy last weekend on a quick overnight outing. This bag was used under a tarp shelter. Overnight temps dipped into the low- to mid-40s. Although bugs weren't an issue, I did use the face net to reduce the breeze/draft on my face. Upon waking in the morning, I was chilled inside my bag inside the bivy. Upon peeling my bag out of the bivy, there was a fair amount of condensation inside. Most of the moisture was on the inside of the bivy. Parts on my sleeping bag, on the outside near the foot, were moist, but not bad. The inside of my sleeping bag felt dry. I had read reviews of the REI minimalist Bivy stating that moisture accumulation could be an issue, so this did not surprise me. I look forward to trying this bivy out more this year.
More-expensive/higher end: Outdoor Research Advance Double Bivy - It is a constructed of a medium weight ripstop nylon with a Gore-Tex laminate. It is a double - made for two people. it has two poles - one that goes around the head area that lends shape to and helps configure the opening, and one that arcs overhead so that the bag material is well off your face.
This thing is awesome. My wife and I have used it for minimalist trips, and there has been plenty of room for us both inside. I have used it on solo trips and have kept my pack inside with me. The large mouth-like opening makes entry/exit pretty easy. Packed it is about the size of a really small two-person tent, or a spacious solo tent, but the single-piece construction (no fly), two short poles, and absence of stakes help keep it light. I have never encountered moisture in this bivy, even when camping along Lake Michigan in summer. This is one of my most favorite shelters. Sadly, I do not believe OR makes a double bivy anymore.
I also have a one-person tent bivy that was handed down to my after my uncle passed away. I have not used this unit, as it always had a funny smell to it. Last fall I decided to run it through a wash cycle in our front loader with some Tech Wash detergent. The oder is still there, but it has been largely minimized. Maybe I'll run it through another cycle one of these days. NOTE: I don't recommend washing any tent or bivy in the wash machine. If you feel you must do so, do at your own risk.
I am not sure of the manufacturer of this bivy-tent thing. It has a mid-weight coated nylon floor and a Gore-Tex laminated to ripstop nylon top. No fly. One thing that makes me leery of using it is it has two fiberglass poles that are very thin stock and are fit-together sections; not shock corded. When pitched, this shelter does provide enough interior room to allow a sleeper to roll onto his/her side and what not, but not sit up. the foot end has a hooded vent, and the slanted entry is mesh with a bungied Gore-Tex flap.
I hope this info has helped you, Noshtero (and others). Happy camping!
