Emergency Mylar Sleeping Bag Test

We wanted to test a mylar sleeping bag to see if they really work. We found that they do have waterproof, wind breaking, heating properties. 

The Experience Test

In 35 degree weather with a moderate breeze and light rain I slid into an emergency mylar bivvy/sleeping bag and went into the back yard. I wore shorts, a t-shirt and flip flops.

I started out warm and dry and stood still within the 7 foot bivvy. I pulled it over my head and synched it up around my neck with my hands. 

Here's what I found:

1. Waterproof: 10/10. I remained dry. No rain water passed through.
2. Wind Breaker: 9/10. I didn't feel the wind. The breeze was light but I couldn't feel it at all on my skin.
3. Heating: ??/10. Here's where it gets interesting. The material is intended to radiate heat produced by the body back to the body. It did that - the radiant properties checked out. I could feel the heat building within. At some point I could see steam coming out around my head. Very cool.
   
   However, the conductive properties are a weakness. The material was pulled tight on my shoulders. They were cold. I decided to take it a step further and stepped of my flip flops onto the grass. I instantly felt the cold of the wet grass. I knelt down and my knees were instantly exposed to the cold temperature. I sat down and started to get cold all over.
   
   I stood back up and back onto the flip flops and could feel my heat radiating back - but this time there was a cold draft.

I went inside the garage to inspect the bivvy. It was torn in 3 places. I hadn't gone anywhere. I had only knelt and sat. The material had failed.

The Results

These emergency coverings are a good backup for normal insulated clothing. They are waterproof and windproof as long as you don't break out of them. 

They work great when you can use their radiant properties. But they don't work at all as insulation. That means sitting or laying down without insulated clothing is not really an option because the ground will suck the heat out of your body.

We still believe these belong in a go-bag because the price and weight to function ratio is still worth it. We also recommend having insulating clothing in your go-bag.