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admin23/03/2010 15:48:58

Compston CornerAmbleside Cumbria LA22 9DS

What is a Windproof ?

   Words by tcsh

   on 12/08/2010 16:25:00

Depending on when you are heading out in to the hills, there are a few main things that will be looking for in a jacket. In the winter it tends to be warmth, and waterproofing, in summer it is breathability and physical weight. There is one factor however, that is needed virtually all year round – Wind Proofing.

Windproof vs Fleece?

fleece-vs-windproof Whether you use a windproof or a fleece really depends on why you are getting cold. If the air is just cold, like it is in the winter then it is often worth getting a fleece on as your body needs the insulation against the cold temperatures. A fleece, like any form of insulation, will trap a layer of air than can warm up with your body heat and therefore keep you warm. That is why, when you exert yourself in a layer of insulation, you very quickly get too warm.

On the other hand, if you are getting cold because of the wind then a fleece often does not work. As a fleece is naturally permeable the breeze will blow through it and continue to chill you. In this situation, a wind proof layer is of more use as the cold breeze cannot get in.

This is particularly useful in summer conditions when you can be confronted by an unexpected cold wind. In this situation a fleece may be too permeable, but it may also make you way too warm when the wind dies down - a windproof keeps this cool breeze off you without insulating your body.

NB: Not to confuse the issue, but you can now get fleeces that are almost completely windproof, without being too bulky. In the past, windproof fleeces relied on just piling the fibres into a fabric so that no wind could reach you, but it ended up a bit like wearing a shag pile carpet! Now, with modern technology, you can get thinner weight fleeces that have such tight knit fleece fibres that wind finds it very hard to penetrate.

So what kinds of windproof are there then?

There are two main types of windproof material; membrane and flash heated.


The idea behind these is that you take a normal garment, like a fleece to a soft shell jacket, and you insert a layer of windproof material into the construction. What you end up with is a fabric that looks very much like the original but is now completely windproof. This is great for incorporating windproofness into standard garments and can be found in many ranges from almost all manufacturers.

image A windproof membrane is nearly always made from a type of plastic. Now don’t panic, we’re not talking plastic bags here, we’re talking about the most advance breathable polymers available - products such as PTFE (the same as they use in Goretex), which are riddled with tiny little holes that allow the moisture vapour molecules that you produce, to percolate through and escape into the environment. These holes are so fine that, although moisture can get through them, they do not allow a breeze to pass through them in return, hence Wind Proof.

The most well known of these membrane technologies is Gore’s Windstopper fabrics (pictured left) which, like Goretex, is used by many brands in their softshells, gloves and fleeces. Polartec, the fleece fabric company, also produce a fabric called Powersheild, which is a windproof soft shell with a built in membrane. They also do Windbloc which is the same but in a fleece version.

NB: Be careful when you are looking at windproof garments, that the item not too cheap, as these can often be made with membranes that do not have a good breathability rating and will be a bit like wearing a bin liner!

Flash Heated Fabrics

These fabrics are completely different to membranes and are used quite differently too. Instead of being buried inside a garment, these windproof fabrics form the outer shell of an item of clothing. Made from very closely weaved synthetic fibres, which repel the wind, these fabrics are also treated to a burst of heat in the inside which fuses the fibre ends together, thus creating a barrier to the chilling breezes. The spaces between the fused fibres are still large enough to allow water vapour through however, thus making these fabrics breathable as well.

The classic (and probably original) flash heated fabric is Pertex, who started life making parachute fabrics, but are still a market leader in this type of fabric technology. Other companies also make their own versions like Haglofs PERFORMAC™ fabric which has many of the same qualities as Pertex.

Ok, so what are the downsides?

Both have their advantages and disadvantages, which one you choose depends on what you are looking for.


As mentioned previously, these are used in combination with other fabrics, and therefore tend to be very comfortable. The combination fabrics act as a wicking liner than enables moisture to be transported away from your body quicker.

This can also be an issue however, when you just want a windproof layer with no insulation. To date, no one really makes a windstopper that is just the membrane. All membrane products are therefore slightly heavy and, in the summer, can be too hot to wear for a prolonged period of time.


Flash Heated

These are super lightweight, as it is just the windproof on its own. That means that you can get a Pertex top like the Montane Featherlite Smock (left) which is smaller than an apple and weighs less than one too!

The downside is that, as there is often no liner, they can feel clammy. Although they are breathing as quick (if not quicker) than the equivalent windstopper, you can often feel the moisture against your skin before it is transferred to the other side.

Ok, so I’m still not sure which one to go for, which one is best?

As always, there is no best. If you are looking for a jacket or pair of trousers etc that keeps the wind out, no matter what, then you would do well to go for a membrane based wind proof garment, such as a Gore Windstopper or a Polartec Powershield.

If you are going to be working hard or in warmer weather when you don’t want your jacket to warm you up as well, then a flash heated garment like Pertex or Haglofs PERFORMAC™ would be more suited to you.

Make sense?

· Umm, yeah, thanks ..... I think I’ll buy both to be on the safe side!

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