My objection to this video is that it might lead an inexperienced person to expect much more than a paper-thin sack can offer. While it does protect from rain and wind, it provides zero insulation. It may reflect 90% of your radiant heat loss back to you, but the losses through conduction, for example, are much larger. Before you need to use one of them in an actual emergency, try one of them out on your front porch on a cold winter night. You will likely find the protection advertised hyperbole. Keep one of these in your backpack, it is better than nothing. However, in my experience, these don't live up to the advertising and the condensation is a serious problem.
Agree, before buying an emergency bivy, make sure it's breathable and has a half length zipper. I have one made by SOL and I have used it many times. I've had the others but this is by far the best.
So there like a Mylar blanket or Tent , so there is no insulation value to them just reflecting heat. Would you not get wet from the condensation? I can see these being great with a debris shelter . . Or great with a wool blanket or sleeping bag . Just not a stand alone blanket or shelter I’m just confused on what is best to have A Mylar bivvy bag Emergency Mylar blankets Emergency Mylar tent 🏕️ All three would need some sort of debris shelter too keep warm What’s best out of the 3. I’ve seen videos with the tent ⛺️ and a beeswax candle 🕯️ That seems practical I guess putting a candle 🕯️ in a bivvy sack might cause some problems 😂
You ask a very good question. I've seen other reviews that indicate that their reflectivity does increase the total heat retention ability whilst protecting the sleeping bag from the elements. Condensation however is a problem.
