Waterproof and Breathability explained

Picture this scene; It’s a cold, dreary start to the day and you’re getting prepared to go on a hunt you’ve been planning for a while.  You gear up and fire on your waterproof, breathable clothing and head out.  The rain starts to fall and, after a while, it gets a little heavier.  Your jacket, trousers and boots repel the rain like it doesn’t even exist.  You have an impenetrable layer against the elements - guaranteeing a comfortable, dry day stalking.   After a few hours of moving around and finding your perfect spot you begin to notice your inner layers feeling damp and you can feel them clinging to your skin.  You immediately assume your waterproof clothing has failed you and that mother nature has won another battle….. but you would be wrong, in most cases anyway.

More than likely this is something some of us will  have experienced at some point during our days stalking and hunting over the years.  When purchasing clothing for the great outdoors we all look for the same thing; our clothing of choice must be; 

• Waterproof

• Breathable

• Wind-proof

With so many fabrics on the market today that claim to be all this and more, it can sometimes be difficult, as a consumer, to decide which is best.  We have GORE-TEX® this, DEER-TEX® that and so many other TEX's that all do the same thing, but differently, it’s no wonder some of us are left scratching our heads.

To make life that little bit simpler I have managed to talk myself into writing a blog explaining what we mean by a garment that is waterproof and breathable.  Hopefully you will be able to use this blog as an aid the next time you purchase your breathable, waterproof clothing from BushWear.

Waterproof

One way to test the waterproofness of a garment is by the static column water resistance test.  This is where a square column measuring 1” by 1” is placed onto the fabric.  It is then filled with water and the level at which the water begins to push through the fabric is recorded.  This recording is measured in millimeters.  So a fabric which states it’s H20 rating or hydrostatic head rating as 10,000mm, means that a column of water 10,000 mm (10 meters) in height showed first signs of water permeating through the fabric at the 10,000mm level.  The higher the rating the more water your garment can resist including pressure against the fabric itself.

The following information will give you some idea as to what sort of level of waterproofness you can expect from a fabric of given rating.

When we talk about pressure we are referring to any external pressure applied to the fabric itself.  Kneeling on the ground or even having a backpack against the fabric increases the pressure against the fabric. This increase in pressure can be enough to allow moisture to seep through the fabric and be absorbed by your inner-layers. This must be taken into consideration when deciding which range of waterproof clothing you would like to purchase. Having a piece of clothing which has a high waterproof rating, but a low breathability rating, is not recommended for all situations. Imagine wearing a black bag; you know you’ll be protected from the rain but with no breathability you’ll be raining sweat on the inside with no where for it to escape.  So lets have a look at what we mean by breathability.

Breathability

The ability of our outdoor gear to allow perspiration to escape is just as important as not letting external water in.  The only issue with the breathability rating of a fabric is that there are three ways to test this - meaning it is not standardised and may vary between manufacturers. However, the breathability of a piece of fabric is frequently measured by g/m²/day - this basically means over the course a 24 hour period the fabric allows X grams of moisture to escape per meter squared of the fabric.  To increase the breathability of a piece of clothing other features are normally incorporated into them.  Features such as mesh lined pockets and pit zips are ideal  for added ventilation.  The following information will give you some idea as to what level of breathability you can expect from an item of clothing with a given rating (g/m²/day).

Now to be honest, I cannot think of a scenario involving hunting or stalking where a low breathable fabric would be ideal.  Referring back to my opening paragraph, if you were to wear clothing which offered high waterproofing levels but low breathability levels you will end up as wet on the inside as your would have done on the outside, if your clothing was not waterproof.

Wrapping it up

As with everything in life the quality of the clothing you purchase is determined by price.  If you want something with high water proofing and high breathability you can expect a more expensive price.  When you begin to sacrifice breathability or waterproofing the price comes down and you basically get what you pay for.  The one thing I always look for when purchasing clothing is to see if the manufacturer lists the levels of breathability and waterproofing.  If one is mentioned and not the other I automatically assume the one which is not mentioned is going to be very low.  If purchasing a garment which is £100 and claims to be waterproofed up to 10,000mm and is stated as breathable, but doesn’t mentioned the value, it’s more than likely going to be below 3,000g/m²/day.  For something to be breathable and waterproof, the rating only needs to be greater than, or equal to, 1,000 in both instances.  As an example look at the Torrent Euro II - Waterproof to 10,000mm with a breathability of 1,000g/m²/day.  I have one myself ,and it’s good for general limited wear, but come the hunting season I know I’m going to grab my high breathing, high waterproof rated clothing.