Post by tiamo on Jan 2, 2012 20:41:29 GMT -5
The main function of a performance outdoor jacket is to keep you dry, warm and allow you to move without restriction. With different GSM fabric weights, waterproofing expressed in MM, breathability in MVP and insulation in TOGs, how do you choose the right jacket for your needs?
The following is intended to give the non-expert consumer some insight into how to make a more informed choice and why the most high spec and expensive jacket may not always be right for you.
Background Information,
Modern high performance outdoor clothing, particularly jackets, are made up of layers of materials with different properties to not only keep water out but also allow your body to breath by venting perspiration keeping you dry and therefore warmer.
This is achieved by bonding together several layers of material with different properties to produce a fabric that is both lightweight and highly functional. These fabrics were first used in garments produced for the north face mcmurdo parka sale military, emergency services and people who have to work outside whatever the weather. It was essential that the clothing provided would allow full mobility keeping the wearer comfortable for prolonged periods.
The technology that produced these fabrics has become more generally available for manufacturers to use in clothing for leisure activities such as climbing, skiing, sailing, cycling, hiking and walking. One of the first and most familiar products that came into common use is Gore-Tex although a wide range of high performance layered fabrics have now been developed for this use.
Fabric Construction
In the fabric sandwich it is the outer layer, or shell, which provides the majority of the wind and waterproofing. Oilskins and rubberised cotton were used to make some of the first truly waterproof clothing as the treatment produced a sealed coating impervious to water. These garments were heavy and difficult to move in and any physical exertion caused perspiration that could not escape through the outer layer of clothing. In time this soaked the under garments which conducted heat away from the body making the wearer uncomfortable and cold.
With advent of man made polymer fabrics it became possible for a more sophisticated approach to waterproofing to be developed. Modern materials have a micro-porous structure which means that the networks of very fine gaps between the fibres are too small to allow water droplets in but will allow perspiration, in the form of water vapour, to pass through and out. These fabrics are termed 慴reathable?
Just how good a barrier to water a fabric is can be determined by the height of a column of water that the material can resist ie 1600, 2000 or 8000mm in height. Most fabrics for outdoor use can shrug off or repel a small amount of water sprayed onto them but to be really waterproof the fabric needs to be able to withstand contact with water under pressure trying to force its way through the micro-pores. The pressure increases with column height, to simulate the worst weather conditions possible ?howling wind and lashing rain, the higher the column height resisted, the more waterproof the clothing.
The next internal layer in the fabric make up is a film that attracts the water produced as perspiration and holds it in contact with the outer layer so that it can be vented or breathed to the outside world. This layer can also help increase the wind resistance of the garment
If higher performance is needed a third inner layer can be added which rapidly moves moisture away from the body keeping it warm. The insulating effect of this layer helps the passage of moisture through to The north face jackets the outside by preventing condensation forming. The heat that is retained vaporises the moisture which is essential in assisting the venting process through the outer layer of the garment. The speed at which moisture vapour will be able to escape through the final article is given as an MVP (Moisture north face mcmurdo parka sale Vapour Permeable) rating again the higher the figure the more breathable the garment is.
The total thickness of the various laminated layers that make up the jacket fabric is given as a grams per square metre weight i.e. 279gsm. Thicker fabrics tend to have higher performance and resist abrasion better but can be less flexible. Thicker sections are often incorporated just on the shoulder areas to overcome this problem.
The final features of a truly waterproof garment are that all the seams should be taped or welded to prevent any moisture gaining access through the stitching also zipped openings should be of a watertight design
Breathability
At this stage it should be pointed out that once a garment is soaked having been in torrential rain for some time or in very humid conditions its ability to breath is significantly impaired. Even though water is not penetrating through the fabric layers to the inside, once the outer layers become waterlogged the passage of water vapour from the inside to the surrounding air outside, is no longer an efficient process.
Regardless of how expensive a jacket is or complex the construction of its layers
in conditions of high humidity on the surface of the jacket or in the air surrounding it migration of moisture away from the source to the drier atmosphere, which makes the fabric breath, will be severely hampered.
If perspiration builds up under waterproof clothing it will eventually evaporate escaping through neck or other openings in the jacket. This larger scale evaporation will take body heat away in the process the resulting chill factor is very uncomfortable and difficult to reverse. Once a jacket becomes soaked the best remedy is to take it off as soon as it is practical and allow both sides of the fabric to dry out.
The highest rated and heaviest most waterproof fabrics are often less breathable than there thinner less waterproof counterparts and when waterlogged will take longer to dry out.
So how do I find a Jacket that works for me?
First decide what is the main activity you are going to be using the Jacket for.
Passive or active and the most desirable properties - waterproofing, warmth or mobility.
For example:
Fishing may require sitting still in the pouring rain for long periods. As no physical exertion is producing perspiration and mobility is not important waterproofing and warmth are the most desirable functions rather than breathability and lightweight construction.
Skiing is a physically demanding activity pursued in cold rather than wet conditions. In this case breathability and thermal insulation are most important.
Functionality such as ease of movement together with insulation for warmth can difficult to achieve in one jacket. Some ski jackets are made from a heavyweight fabric to give warmth, but with a soft outer shell that makes the jacket very flexible and easy to move in.
Clothes layering
Another way to gain more adaptable all weather protection that can be modified as conditions dictate is to extend the layering principle to the clothes worn under the top jacket. In this system warmth, windproofing and moisture adsorption are performed by the underwear and middle garments. The outer jacket provides the waterproofing and breathability.
In extreme conditions thermal underwear, which is of a cellular construction, to trap warm air next to the body, is combined with a fleece top. The fleece absorbs perspiration and wicks it away from the body, it is warm and offers enough windproofing to be worn as an outer layer in dry conditions. Higher spec fleece抯 offer good all round protection, including a degree of water resistance and are extremely light and easy to move in. They are ideal for the more physical forms of activity such as climbing and cycling as perspiration will not be trapped. When more substantial waterproofing is needed a lightweight breathable jacket is added which is very flexible and dries the north face sale out quickly after soaking.
Fleece抯 that are designed to fit together with outers are available in what are called 3 in 1 jackets. The outer can be worn on its own, so can the fleece or they can be worn together. Buying a 3 in1 jacket ensures that the properties of the outer jacket and fleece match and that they fit together properly.
Effective clothes layering requires that each layer fit correctly so that air and water vapour circulation is controlled. Too tight and the wearer will be cold and find movement restricted. Too loose and the chimney effect will occur, good in the desert when you want to loose heat, warm air rises and escapes from the jackets neck opening drawing in cold air behind it not desirable in cold conditions.
Hopefully advice will be available where you buy your jacket but it is always useful to have a good idea of what it is you need in terms of functionality before branding, fashion and price confuse the issue.