Inner or base layer

The purpose of the inner layer is to draw sweat away from the skin to the outer layers to feel warmer. The transfer of moisture happens due to capillary action, sometimes called wicking. The used materials are called 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 does not transfer moisture well, it is not strictly an inner layer garment at all but simply a comfortable mid-layer garment.

• Wool has a combination of wicking and water-repelling properties^[1] and is highly odour resistant.^[2]

Mid layer

The mid layer is needed in cold weather to provide additional insulation. The use of multiple thin layers facilitates the adjustment of warmth. The mid-layer should be more loose-fitting than the inner layer, as this leaves insulating air between the layers. However, if the best possible moisture transfer is desired, too great a gap between any adjacent layers of clothing may reduce the moisture transfer by capillary action from one piece of clothing to another. Conversely, layers that are extremely loose-fitting can facilitate the increased elimination of moisture and heat, owing to enhanced air circulation.

• Wool, a traditional material used for mid-layer clothing, possesses several beneficial properties. It provides effective insulation even when damp, has the capacity to absorb moisture without imparting a wet sensation, and facilitates efficient moisture transfer.
• 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 to weight ratio, and can be compressed to take up very little room. On the downside, it is expensive, makes 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 to weight ratio. However, it is less expensive, provides better insulation when wet, dries quickly, and absorbs very little moisture. There are brands of very fine fiberfill, like Thinsulate, PrimaLoft or Thermolite, that provide 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.

Shell layer

A waterproof breathable (hard shell) jacket

The outermost clothes are called the shell layer, but only if they block wind or water or have good mechanical strength. 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 slight trade-off between breath-ability and water- and wind resistance.

If heavy sweating is expected, one should avoid wearing any shell layer garments unless their protective properties are essential. For example, when one is jogging, no traditional shell layer is likely to be able to transfer enough moisture to keep the wearer feeling dry. But as more air permeable membranes emerge, when combined with pit zips the amount of moisture being transferred outwards would be sufficient for cardiovascular activities. As a general rule, one should consider using sufficiently warm mid layer clothes.

Both "soft" and "hard" shell jackets and layers exist. Hard shells are commonly woven fabric and do not rip. Soft shell may rip more easily, but are more flexible.

• Plastic raincoats protect completely from water and wind, but let no moisture through. To compensate for that, raincoats usually have flap-covered holes and are very loose-fitting at the bottom 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. Well-known brand, Gore-Tex, has the best breathability, although it has less wind resistance.^[3]
• Water resistant (soft shell) materials generally block water only partially, but more fully waterproof soft shells are emerging such as polartec neoshell or DryQ Elite. 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. Soft shells are not water "proof".

The term soft shell is increasingly used to describe garments that combine partial or full water resistance with partial or full wind breaking ability. Soft shell fabrics come in numerous varieties with many garments offering a combination, such as a wicking layer. In many cases insulation is combined in an attempt to replace several layers with a single highly flexible one. One of the most unique characteristics of the woven soft-shell fabrics is the combination of windproof, a high level of water resistance, and stretch -- in many cases four-way stretch. Solid plastic films and micro-perforated laminates typically breathe much less and do not stretch at all.

Vents

Some clothes feature adjustable vents, such as below armpits. The positioning and design of the vents allow for area specific cooling while only marginally reducing exterior moisture resistance.

Removing layers

Removing the shell layer during heavy exercise can pose problems if the clothes underneath lack required mechanical strength or waterproofing. In such situations, using a mid-layer with enough of the required shell layer properties can be a good choice.