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Waterproof and Breathable - Breathability Explained

Breathability and Waterproofness


Hi Guys. So, you are looking for a new coat, but you are not sure what breathability means?  I am going to do my best to explain and also to give you an insight into waterproofness.

When we consider buying an outdoor coat most of us will be wondering if it is going to be waterproof, it will not be many of us whose first thought will be its breathability, yet this is a very important aspect of a coat. Even some of the most enthusiastic of outdoor people do not often think of the breathability aspect of their clothing.

Breathability is the ability of the fabric to absorb moisture and release it through the material itself allowing it to breath and not be suffocated by the moisture within it, causing sweat to build, moisture to form on the inside and smells to linger in and on the fabric.

If you are an active outdoors enthusiast and you want to boost your performance a breathable garment will ensure this enables this to happen. Breathability is a crucial element in the technicalities of performance wear.

The breathability of fabric that has a continuous motion of absorbing and releasing moisture, such as sweat, should have a higher perspiring capacity within it.

There are many reasons that breathability is important: it can prevent you from overheating. Fabrics that are designed to be warm should have a breathability factor to prevent the wearer from becoming stuffy and producing to much sweat, whilst wearing.

If your jacket is breathable but you are wearing layers beneath that are none breathable then your system will fail and all will become non breathable this means that sweat cannot make it to the breathable layer and will stay inside your clothing.

Breathability also allows air to travel through the fabric, repelling odours and keeping the cloth fresh.

If you were buying footwear, you should also buy shoes, boots, etc with a breathability fabric as this can prevent blisters. An excess of moisture build up from a non-breathable boot can cause excess sweat, causing rubbing and, which, in turn leads to blistering.

Outdoor clothing can contain a breathable, microporous, membrane, which are thin layers of man-made film containing tiny pores which allow vapour to be released but are too small to allow water droplets in. These layers are either 2 or 3 layers thick and are laminated to the face fabric.

The 2-layer version is normally featured in lined-garments where the lining protects the membrane.

The 3-layer version is where the membrane is sandwiched between the outer and inner layers of fabric.

Sometimes mesh is incorporated into clothing as an added breathability aid. Also pit-zips can be found under the armpits of some garments which can be fully opened to allow your armpits to cool if you are overheating but unable to remove your clothing due to outside elements.

At the moment there is no standardised way of testing breathability, but most use the MVP guide to rate their clothing.

MVP stands for Moisture Vapour Transmission and is dependant on the formation of a temperature or pressure gradient between the interior and exterior of the breathable garment. Breathable fabric works by equalling the heat and pressure inside and outside the garment, constantly adjusting one way or the other to keep them in balance.

When you sweat the moisture inside the clothing must pass through the fabric and evaporate on the surface, if however, the passage for this to happen is blocked the build up of moisture has nowhere to go and thus builds up on the inside of the clothing causing condensation on the inside and making the user uncomfortable.

Breathable fabrics work best when the air inside is warm and humid and the air outside is cold and dry.

Breathable clothing is best worn close fitting due to the fact the moisture vapour build up which is on its way out will come into pockets of cooler air between the middle and outer layers and so the condensation should form on the outside.

MVP measures the amount of water vapour that can pass through a square meter of fabric in a 24-hour period:

8000g will give you a good level of breathability for general outdoor use

20000g gives you a good level of breathability for more active use

30000g gives you the best level of breathability.

Waterproof fabrics are resistant to water penetration and usually have a membrane or coating which acts as a barrier and causes non-saturation into the material.

Waterproof ratings are thus:

5000mm this is the minimum rating that an item can be to call itself waterproof and will only be waterproof in a light shower

1000mm-15000mm will withstand a downpour and heavy snow., but if you are out to long eventually the wet will penetrate through the fabric causing wetness

20000mm and above if you are planning to work or be outside in very wet weather for long periods you should look for this rating to make sure you stay waterproof all day.

If your item is water resistant it is NOT waterproof. Water resistant means the item is able to resist the penetration of water to some degree, but it can soon give in and become wet.

So just to sum this up:

Breathable can dispel the build up of condensation and allow any build up of moisture, including sweat, to be expelled.

Waterproof, depending on the rating, will cause water to run off the garment and not penetrate through to the inside.

Water resistant will cause a light amount of water not to penetrate.