What's a Mylar Blanket and How Does It Work?
Mylar blankets have powerful heat reflective qualities that can be beneficial to anyone struggling with winter heating insecurities.
Derived from NASA technology, the common name for these sheets of foil is 'space blankets'. Also known as solar blankets, Mylar emergency blankets, they help people stay warm. They are efficient, light weight and reliable.
Mylar can reflect the wearer's body heat back
So, how exactly can a paper-thin sheet help hold in heat?
Manufacturers created the material by depositing vaporized aluminum onto a very thin plastic film. The resulting material is thin, flexible and thermal-reflective -- meaning it reflects heat. The aluminum helps redirect infrared energy. Depending on how the blanket is made, it can reflect heat away (that's how NASA used it to cool down Skylab), or it can reflect heat in (that's how it regulates body temperature). Sometimes called a passive warming system, space blankets assist the body in conserving that infrared energy.
Conduction is the transfer of heat or cold between two objects. For example, if you sit down on a pile of snow, your backside will get colder, and the snow will get warmer. With convective heat loss, however, the cold object is moving -- like a cold wind. The wind takes the warmth away from whatever it touches. The faster the object is traveling, the colder you'll get. You can help reduce convective heat loss by wearing layers of clothing as insulation. A space blanket forms a barrier between the wearer and the wind, providing insulation.
Lastly, we also lose body heat through radiation -- it simply radiates off our body. The reflective agent on space blankets -- usually silver or gold -- reflects about 80 percent of our body heat back to us.
Information used from https://adventure.howstuffworks.com/survival/gear/space-blanket.htm