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Waterproof Breathable Material Does Not Exist!

Physics tells us that getting the sweat while in a vapor state out of a rain garment cannot be done, at least not in the manner that has been advertised for years.

Every person reading this article and every person who does not read the article has experienced the same thing when it rains and that is the drop in ambient air temperature. When it rains the ambient are temperature will drop because the rain water is descending from an altitude where the ambient air temperature is lower than on the surface of the earth. Therefore, the water temperature will be whatever the ambient air temperature is at altitude. I became very aware of this action when I started sailing. I was sailing in Long Island Sound during the summer when temperatures were in the 80s and 90s. When a squall happened the temperature would drop very quickly 20° or more in a matter of minutes.

Air at a higher temperature will hold moisture. Hurricanes are formed over the equator and require warm water which evaporates and this moist air now joins the wind. At some point the moist air will cool and then we have rain. The cool air does not retain the moisture as a vapor.

The human body has a core temperature of 98.6° and as that temperature increases the human body via involuntary action starts sending the excess heat to the skin surface. Also out of the pores of the human- body flows moisture known as sweat which is also in the 90° category. Initially the moisture comes out as a vapor but it quickly cools and turns to a liquid.

If the moist vapor could stay in the vapor state once it reaches the inside surface of a rain garment which is cooler than the vapor the vapor will condense and the inside of the rain garment will become wet. In reality the moist vapor will condense on the skin surface without ever reaching the inside of the rain garment.

In order for the moisture as a vapor to actually move through the fabric that has been laminated to a film there would need to be air pressure that is warm enough to keep the vapor in a vapor state.

Now that we understand why moisture as a vapor cannot ever get out of a rain garment we must examine what can be done to minimize the unpleasantness of the clamminess. The answer is a certain level of insulation. But if you add insulation to the garment, won’t that make you hot, no! Remember when it starts to rain the temperature drops, so some insulation is necessary. But what about when it is not raining, the level of insulation that I believe necessary would not be for arctic purposes but for 40° and warmer. The reason for the thin layer of insulation is to allow the moist vapor to move from your skin surface through the insulation so it will condense between the insulation and the inner side of the exterior of the shell material. If the fabric is vapor permeable when the rain stops and the temperature increases you will experience some of the moisture on the inside evaporating through the fabric so long as it is not coated or laminated to any film.

For the most efficient rain coat see the Wiggy’s DUCKSBACK Zippered Jacket.

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