Outdoor Clothing - Three Layer System

Outdoor and Hiking Clothing used to be any combination of day to day items of clothing which were used to keep you warm and dry. Nowadays, the generally-accepted way of getting yourself dressed for Hiking and Outdoor Activities is to use a Three-Layer System. In this section, know what the

Three Layer System is and what the layers are:

1 - Base Layer / Thermal Underwear

The Base Layer is the first layer of clothing you put on and it is in direct contact with your skin. For Outdoor Activities, it is very likely that you will be sweating, cooling down, sweating, cooling down, etc. It is important that your clothing works in a way that it can cool down quickly but not too much. This is where the base layer comes in:

Purpose of the Base Layer
A common problem in many Outdoor Activities is 'after-exercise chill'. Cotton T-shirts and other common underwear capture the moisture of sweat in their fabric and after your body has already cooled down and stops sweating, the wet cotton will keep on cooling your body down. Not only is this uncomfortable, it also forces your body to increase its heat production and it increases the chances of under cooling. The base layer should not retain moisture but transport it away from the skin, thereby countering 'after-exercise chill'.

Base Layer Materials
The materials used for Base Layers change constantly as manufacturers come up with new high tech synthetic fabrics or re-invent older materials like wool. In general, they all have common characteristics:

  • The materials absorb only a very small percentage (< 1%) of their weight in moisture. In practice, this means that they retract moisture from your skin and dries very quickly.
  • The fibers are very lightweight but very durable.
  • They are treated to decrease the tendency of base layers to itch and smell due to body odors and/or fungi.
2 - Insulation Layer

The Insulation Layer is the second layer of clothing which is put on after wearing the base layer. The purpose of the Insulation Layer is to retain body heat and the best way to do so is by creating a layer of still or dead air around your body. This still air will seriously decrease the heat exchange between your body and the outside world.

Fleece / Bunting / Pile
The Insulation Layer mostly consists of polyesters that are treated in a way that makes the fibers stand up and trap air between the fibers. This trapped air forms the protective layer of still air forming the main insulation. The most popular materials are:

  • Fleece - Fleece is mostly made out of polyesters. A dense knit of polyester fabric is taken and passed through a 'napping' machine. On one side of the fabric, the machine will pick out and rake up the fabric loops, creating a fabric with a tight solid weave on one side and a fluffy air retaining surface at the other side.
  • Bunting - This is fleece that has been 'napped' on both sides, creating a tight solid weave with wooly air retaining at the surfaces on both sides.
  • Pile - This is single-sided Fleece that has undergone more 'napping' and has been processed further to create a much thicker open fabric.

Characteristics of Fleece / Bunting / Pile
Fleece, Bunting, and Pile combine a few characteristics that make them so suitable as Insulation Layer materials. First of all, they posses the ability to retain still air which insulates and prevents body heat loss as outlined above. Besides this, the treated Polyesters used have almost the same moisture-transporting qualities as Base Layers. They transport moisture to the outer layer and dry very quickly.

3 - Outer Shells

The Third and final Layer in the Three-Layer System is the Outer Shell which is the only layer with direct contact to the outside world. The Outer Shell serves three main purposes:

  • Protection from wind and outside moisture like rain and snow.
  • Getting rid of body moisture
  • Protection from chafing, cuts, scrapes, and other outside damage.

Before high tech fabrics were developed, these purposes were performed by separate pieces of clothing. Nowadays, however, Outer Shells can be waterproof, shock-absorbing, and breathable windbreakers.

Outer Shell Materials
The theory behind Outer Shell materials is the fact that a water drop is much larger in size than a water vapor molecule. In essence, combining waterproofness with breathability boils down to finding a membrane with a pore size much smaller than a water drop but much bigger than a water vapor molecule. In 1976, Gore-Tex was developed which is a membrane of a petrochemical polymer called polytetrafluorethylene (PTFE). Since 1976, many variations of Gore-Tex have been developed which fall under the category name of PTFE laminates.

Judging Waterproofness
Keeping outside moisture out is probably the most important task and, unlike breathability, waterproofness depends on more than just the fabric. Here are some guidelines on judging waterproofness:

  • The most important factor remains the fabric. For an outdoor clothing Outer Shell, a score of 40 psi would signify a good state of waterproofness.
  • Seams - Just like in Outdoor Tents, seams are the vulnerable spots in Outer Shells. Seams should be sealed and coated well to prevent leaking. If possible, look for as little seams as possible and avoid seams in vulnerable places such as shoulders and upper back.
  • Zippers - Zippers are another weak point in your defense against moisture. Nowadays, waterproof zippers do exist so ask around. Otherwise, look for zippers that are well-shielded.

Using this Three Layer System gives you the best possible protection from outdoor conditions. At the same time, the system is flexible enough to change specific parts for better, worst, or specific conditions. In most cases, the Three Layer System pertains to upper body clothing. The torso and neck area are the most important things to insulate as they protect your body core. In extremely cold conditions, however, this Three-Layer System can be used for full body protection.

/home/t27bsa/public_html/data/pages/resources/layering/home.txt · Last modified: 2009/08/13 10:47 by Charles Doak
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