SensiblePrepper does a nice job reviewing this SOL Emergency Bivvy sac by Adventure Medical Kits. I have a similar bivvy made by AMK but this is the top of the line bivvy that they make. If you’re looking to put together a nice bug out bag or even for your vehicle kits, be sure you include a good personal shelter option such as this one.
Let me clarify one other point: the popular mylar emergency blankets are HORRIBLE! Do NOT rely on them for your personal safety whatsoever. At best they are able to block the wind but will retain no body heat. And, I’m sure this isn’t foremost on your mind, they are noisy as anything. Even if you’re dog-tired you may find that they are impossible to sleep with, especially light sleepers like me. Bivvy sacs are far quieter.
Bivvy sacs are worth the money. While they’re not rated for extremely cold weather they are usable down to 50 degrees and will keep the elements out, including rain. It’s lightweight, durable, and packs down well. Watch the review to learn more.
Also, if you’re packing for your children as well, ensure you buy one bivvy for each person. I know it can get costly to do so but if you ever really need to rely on them, they may be worth every penny.