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Summer or Winter Shelter Basics Part Three

Saturday 1st February 2014

Summer or Winter Shelter Basics Part Three

(go back to parts one or two)

As mentioned in Part Two, Mylar can be very effective when used properly. When Mylar is used as some sort of clothing or bedding, it is intended to warm you up, not keep you warm. Because it is made from a non-porous material it does not breath and therefore causes moisture to condense and be trapped on the body side of the material. If you are laying on or are wrapped up in Mylar, you will eventually become wet once you have warmed up. Once you are wet, you will become colder and Mylar has now become your enemy. Mylar can keep you from freezing in extreme cold temperatures but generally should not continue to be used as clothing once your body temperature has normalized.

Basically, Mylar has the heat transfer properties of a piece of glass, such as a window. When it is cold outside but warm inside, the window will be cold. So will Mylar. This means you need to do at least two things and three or four if possible. The first requirement is to insulate your skin from the Mylar so that the cold Mylar doesn't make your skin cold. If your skin is cold your body heat can not overcome the cold. The second is to insulate the Mylar from the cold. In other words, wrap yourself in a Mylar blanket and then put your jacket, another blanket or something outside the Mylar to keep it from getting too cold. These two steps, each requiring a very thin layer to make a difference, will allow your own body heat to help keep you warm.

The third option is to add an external source of heat. In the diagram in Part Two it is a fire with additional Mylar or other reflective material used as a shelter which reflects the additional heat back to you. This is ideal and can actually overcome extreme cold temperatures. Where possible, stretch another sheet of Mylar across two verticle sticks on the opposite side of the fire to reflect even more heat into your shelter.

You can increase the efficiency of Mylar even further by using a multilayer Mylar blanket/sleeping bag/tent etc. The multilayer versions include a non-woven nylon laminate on one side that gives the mylar device tear resistance so they last longer. They also help collect the suns heat in the winter instead of reflecting it away. You still treat them exactly the same as plain Mylar as far as the steps mentioned above; you just get a couple of additional benefits.

The last step that can make a huge difference under extreme conditions is to share body heat inside the Mylar blanket/jacket/poncho/sleeping bag etc. As long as you are dry, you do not need to remove any clothing; just let two or more bodies' heat reflect inside the Mylar device to increase the warmth being generated for both or all to benefit from.

Remember, use Mylar to get warm once cold. It is dangerous to count on a Mylar device to keep you warm long term. You should have or find other appropriate shelter and sources of heat to maintain your comfort level long term. 

(go back to parts one or two)

About the author: Jim Higgins

Jim Higgins