Breathability

From snowheads

This is a really nice way to talk about the problem of sweating!

Basically when we exercise we warm up. Our bodies perspire and the African savanna winds evaporate this perspiration to cool us down.

The problem is caused when we go to unnatural places (like snowy mountains) and do unnatural things (like covering up!) In this situation the moisture is trapped in our clothing and builds up. Then, when we stop exercising the cold environment cools this extra moisture and makes us feel cold and wet - ugh!!

The problem is that if you cover yourself in a waterproof material, you stop the rain getting in but you also stop the moisture getting out.

What is needed is a way to get rid of this excess moisture without letting the rain in - science to the rescue (or engineering anyway).

Years ago those nice people at Gore discovered that if you made really small holes in a bit of plastic then water vapour could get out but water drops couldn't get in.

From these humble beginnings came the infamous Gore-tex and, nowadays, many other similar fabrics.

So, should we all have Gore-tex jackets? Well, therein lies a problem. You see they may be very nice people - but they're fairly greedy too ;) As a result, jackets with the Gore-tex label tend to be fairly pricey.

[edit]

Alternatives

There are two (?) kinds of alternatives: coatings and membranes.

Coatings: are applied to lesser fabrics and frankly, don't offer the same performance as membranes (however, don't be put off by the word "coated" - waterproof materials are often given an extra coating to help them stay dry - confused? read more)