The short version
Check the kit list wording, because many races now specify a bivvy rather than a blanket. A foil blanket weighs almost nothing, costs a couple of dollars and is nearly impossible to keep wrapped around you in wind, which is exactly the situation it exists for. A bivvy is a sealed bag you climb into, holds heat far better, and costs around twenty five dollars for a few extra ounces. If you actually needed one, you would want the bivvy.
Common questions
What does an emergency shelter actually do?
It reflects radiant heat back and blocks wind, which slows heat loss. It does not produce heat. Someone who has stopped moving in cold wet conditions is losing heat faster than they can generate it, and the shelter buys time rather than solving the problem.
What are the signs of hypothermia?
Shivering that will not stop, clumsiness, slurred speech, confusion and unusual behaviour. Someone who stops shivering and becomes drowsy is worse, not better. Get them out of the wind, insulated from the ground, into dry layers, and call for help. This is a medical emergency.
Do I need both?
No, but it is common to carry a bivvy for yourself and a foil blanket as the thing you can give away to someone else in trouble. At a dollar each, the blanket is the cheapest useful thing in a vest.
At a glance
| SOL Emergency Bivvy with Whistle | Mylar Emergency Blankets, 6 pack | |
|---|---|---|
| Form | Sealed bag | Flat sheet |
| Usable in wind | Yes | Barely |
| Weight | Around 3.8 oz | Around 2 oz |
| Cost | Around twenty five dollars | Around a dollar each |
| Reusable | Yes, carefully | Rarely |
| Accepted by strict kit lists | Usually | Sometimes |
Choose the SOL Emergency Bivvy with Whistle if…
Your race specifies a bivvy, or you train alone in the mountains. Getting into a bag is something a cold, tired, shaking person can manage. Wrapping a sheet of foil around yourself on a windy ridge is not. It also traps the moisture you are producing, so expect to be damp as well as warm, which is a fair trade when the alternative is hypothermia.
Check SOL Emergency Bivvy with Whistle on Amazon
Choose the Mylar Emergency Blankets, 6 pack if…
Your kit list accepts a blanket and you want the lightest legal option. A foil blanket is genuinely better than nothing, it packs to the size of a deck of cards, and buying a multipack means you can keep one in every vest and drop bag without thinking about it. Practise opening one before you need to, because they are awkward the first time.
Check Mylar Emergency Blankets, 6 pack on Amazon
Related
Comparison based on published manufacturer specifications and the general consensus of owner reports. We have not tested these products side by side. Confirm current specifications and prices before buying. As an Amazon Associate we earn from qualifying purchases, at no extra cost to you.