Layered clothing
From Wikipedia, the free encyclopedia
Layered clothing means dividing clothes to layers that are worn on top of each other. Each layer has different, largely non-overlapping functions. Using more or fewer layers, or replacing one layer but not others allows for flexible clothing to match needs of each situation. Two thin layers can be warmer yet lighter than one thick layer, because the air trapped between layers is a good insulator.
Layered clothing is particularly relevant in cold climates, where clothing must at the same time transfer moisture, provide warmth, and protect from wind and rain. In a hot and dry climate clothes have very different functional requirements: they must block the radiation from the Sun, and allow for sufficient air circulation. Therefore layered clothing in the sense used in this article isn't very relevant to hot and dry climates.
Outdoor and sports wear manufacturers favor layered clothing because, among other reasons, it allows them to offer so called "technical" or "functional" clothes which are optimized for the particular demands of a specific layer. Such clothes are often made of advanced synthetic materials, and can be expensive.
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[edit] Layers
Usually at least three layers are identified as following.
- Inner layer provides comfort by keeping the skin dry. Also called base layer.
- Mid layer provides warmth. Also called insulating layer.
- Shell layer protects from wind and water. Also called outer layer.
Often clothes combine two adjacent layers, for instance in the case of warm undergarments that provide both comfort and insulation.
[edit] Inner Layer
The purpose of the inner layer is to draw the sweat away from the skin to the next layers, which makes the wearer feel warmer and more comfortable. The transfer of moisture happens due to capillary action. This is sometimes called wicking, and thus the used materials wicking materials. When moisture has moved from the skin into (nonabsorbent) clothing, it has more surface area and will evaporate faster. If a piece of clothing doesn't transfer moisture well, it's strictly talking not an inner layer garment at all, but simply a comfortable mid layer garment.
- Synthetic materials such as polyester or microfiber-based fabrics are good choices as they don't absorb moisture but may transfer it well. Downsides are that they can be expensive.
- Silk feels more comfortable, but is weaker and harder to take care of, and is less commonly used.
- Cotton is cheap and feels comfortable when dry but it absorbs moisture easily and is slow to dry out, especially in cold conditions. Cotton is better suited for the middle layer.
[edit] Mid Layer
The mid layer is needed in cold weather to provide additional insulation. For maximum warmth multiple thin mid layers can work better than one thicker. The mid layer should be more loose fitting than the inner layer, as this leaves insulating air between the layers. However if best possible moisture transfer is desired, there shouldn't be a too great gap between any adjacent layers of clothing, as that will reduce the capillary action based moisture transfer from one piece of clothing to another.
- Wool is the traditional mid layer material with several good properties: good insulation even when wet, absorbs moisture but doesn't feel wet even when it hold significant moisture, transfers moisture.
- Fleece made from PETE or other synthetics has many of the features of wool, but is lighter. It provides good insulation even when wet, absorbs very little moisture, and dries quickly. Although no longer commonly used in the industrialized world, natural sheepskin fleece could also serve the mid layer function.
- Down has a very good warmth:weight ratio, and can be packed down (squeezed) to take very little room. On the downside, it's expensive, makes for a thick garment, dries slowly, loses its insulating properties when wet or compressed, and stops lofting properly after being washed several times.
- Synthetic Fiberfill such as polyester fiber is used similarly to down, but does not have as good a warmth:weight ratio. However, it is less expensive, provides good insulation even when wet, dries quickly, and absorbs very little moisture. Thinsulate is a brand of very fine fiberfill that provides higher warmth for a given thickness.
- Cotton, as with the inner layer, is a cheap alternative, but a reasonable choice only when low insulation and moisture transfer is needed.
[edit] Shell Layer
The outermost clothes are called the shell layer but only if they block wind and/or water. If wearing, for example, just an undershirt (inner layer) and a fleece jacket (mid layer), there is no shell layer. Ideally the shell layer lets moisture through to the outside (that is, is breathable), while not letting wind and water pass through from the outside to the inside. While this is enabled to some degree by modern materials, even the best and most expensive materials involve a trade off between breathability and water/wind resistance. The shell layer clothes may also need to have good mechanical strength.
- Plastic raincoats protect completely from water and wind, but let through no moisture. To compensate for that, such raincoats usually have flap-covered holes and are very loose fitting at the bottom so as to allow air circulation.
- Waterproof breathable (hard shell) materials are waterproof and somewhat breathable. Their essential element is a thin, porous membrane that blocks liquid water, but lets through water vapor (evaporated sweat). The more expensive materials are typically more breathable. The best-known brand is Gore-Tex.
- Water resistant (soft shell) materials block water only partially. On the other hand they are usually more breathable and comfortable, thinner, and cheaper than completely waterproof materials. Water repellent coatings are often used. Before waterproof-breathable shells were invented, the "60/40" (60% cotton, 40% nylon) parka was widely used. While the soft-shell approach has never actually gone away (UK company Buffalo making its pile-lined Pertex shelled garments since the 70s, for example) it has expanded greatly in recent years, with the term "soft shell" itself being created with the recent upsurge in interest and use. Soft shell fabrics come in numerous varieties with many garments combining different fabrics. In many cases these garments will include insulation, aiming to replace several layers with a single highly flexible one.
