The layering System

dannah layering system

The laying system

Layering your clothing is a tried-and-true way to ensure your comfort in the outdoors. The beauty of this simple concept is that it allows you to make quick adjustments based on your activity level and changes in the weather.

Each layer has a function. The base layer (against your skin) manages moisture; the insulating layer protects you from the cold; the shell layer (outer layer) shields you from wind and rain. You simply add or subtract layers as needed.

Your Base Layer: Moisture Management


This is your next-to-skin layer. More than any other layer, the base layer helps regulate your body temperature by moving perspiration away from your skin. Trapped inside your clothing, perspiration can leave you chilled or damp no matter how well your shell layer fends off rain and snow.

Keeping your skin dry is important for maintaining a cool body temperature in the summer and avoiding hypothermia in the winter. If you’ve ever worn a cotton T-shirt under your raincoat while you walked, you probably remember feeling wet and clammy, even though you weren’t getting wet from the rain itself. Cotton is an example of a fabric that retains perspiration and can leave you vulnerable to unwanted chills.

For outdoor comfort, your base layer should be made of merino wool (popularized by brands such as SmartWool, Ibex and Icebreaker), synthetic fabrics (such as Capilene, PowerDry and CoolMax polyester) or, for a few uses, silk. Rather than absorbing moisture, these fabrics transport (or “wick”) perspiration away from your skin, dispersing it on the outer surface where it can evaporate. The result: You stay drier even when you sweat, and your shirt dries faster afterwards.

Examples: A base layer can be anything from briefs and sports bras to long underwear sets (tops and bottoms) to tights and T-shirts. It can be designed to fit snugly or a loose fitting, fine-mesh garment. For cool conditions, thermal underwear is available in light-, mid- and expedition-weights. Choose the weight that best matches your activity and the temperature.

Your Middle Layer: Insulation


The insulating layer helps you retain heat by trapping air close to your body. Polyester fleece vests, jackets and tights are classic examples of insulation ideal for outdoor activities. They not only trap air but are also made with moisture-wicking fibres to help keep you dry.

Natural fibres such as wool and goose down are excellent insulators. Wool sweaters and shirts (especially the new generation of merino wool products) offer soft, reliable warmth and keep on insulating even when wet. For very cold and dry conditions, goose down is an excellent choice. It offers an unbeatable warmth-to-weight ratio and is highly compressible. Down’s main drawback is that it must be kept dry to maintain its insulating ability.

Classic fleece such as Polartec 100, 200 or Thermal Pro polyester and other synthetic insulations such as Thinsulate provide warmth for a variety of conditions. These are popular insulators because they’re lightweight, breathable and insulate even when wet. They also dry faster and have a higher warmth-to-weight ratio than even wool. Classic fleece’s main drawbacks are wind permeability and bulk (it’s less compressible than other fabrics).

Like thermal underwear, fleece garments are available in 3 weights for different uses:

  • Lightweight for aerobic activity or mild climates.
  • Midweight for moderate activity or climates.
  • Expedition-weight for low activity or cold climates.

Examples: For high-energy activities such as cross-country skiing, biking or running, choose lighter-weight fleece to avoid overheating. Tights or tops made of Polartec 100 or Polartec PowerDry are excellent for this. For very cold conditions, try thicker fleece such as Polartec 200 or 300.

Wind fleece such as Polartec WindPro polyester or Gore WindStopper adds a high level of wind resistance to fleece. It accomplishes this via a hidden membrane, The membrane can affect the breathability and are best used as soft outer garments in dry conditions.

Your waterproof Layer: Weather Protection


The waterproof or outer layer protects you from wind, rain or snow. waterproofs range from pricey mountaineering jackets to simple windproof jackets, but most are designed to block precipitation and hold in your body heat while allowing water vapour to escape. Most are treated with a durable water repellent (DWR) finish to make water bead up and roll off.

An outer shell is an important piece in bad weather, because if wind and water are allowed to penetrate to your inner layers, you begin to cool off. Furthermore, without proper ventilation, perspiration can’t evaporate but instead condenses on the inside of your shell.

Fit is another consideration. Your shell layer should be roomy enough to fit easily over other layers and not restrict your movement.

Fabric Weights

Though classified as “underwear,” every top in this category is appropriate for use as a stand-alone garment. Micro weight and lightweight T-shirts are standard summertime attire for active outdoor types—when hiking, riding, climbing, taking training runs, you name it—and they’re excellent for gym workouts.

When selecting tops and bottoms for use as base layers (actual underwear), anticipate the conditions you’ll face when choosing the heft of the fabric. Here are our general guidelines:

  • Micro weight: For mild to cool conditions.
  • Lightweight: Cool to moderately cold conditions.
  • Midweight: Moderately cold to cold conditions.
  • Heavyweight: Cold, frigid or blustery conditions.

Some people get cold easily. If so, consider choosing a heavier fabric. Just avoid overdoing it. If conditions become unexpectedly mild, a mid-weight or heavyweight first layer could feel a touch too toasty during vigorous activity.

Tip: Always carry a spare micro or lightweight top on my outings. They weight very little and dry very fast. At the end of a sweaty day I can change out of my “motion” shirt and into my “resting” shirt. This allows me to hand-rinse or air-day my motion shirt in preparation the next day. It’s a nice little luxury.

A few words on fit: The warmer the conditions, the looser you want your base layer to be. Snug-fitting base layers keep body-generated warmth close to your skin, boosting comfort in cool conditions. When temperatures heat up, it’s best to let your next-to-skin layers hang loose to accommodate lots of air circulation. If a garment’s advertising promotes an “athletic fit,” figure its fit will be on the snug side.


Why Wicking Underwear Beats Cotton

Wicking underwear:

  • Efficiently transports perspiration away from skin.
  • Dries much faster than conventional cotton underwear.
  • Reduces the risk of dramatic swings in body temperature.

In very windy or extremely cold conditions, such advantages are potentially life-saving.

Base Layers



This refers principally to polyester and polyester blends. Some underwear blends use high percentages of nylon (as a means of increasing abrasion resistance), or they add small amounts of spandex or elastin (to enhance stretch). Polyester, though, is the dominant synthetic fibre used in wicking first layers. It’s a soft, easy-care fabric with reliable moisture-management attributes.

Additional pros:

  • Lightest in this group.
  • Abrasion-resistant.
  • Wrinkle-resistant.
  • Easy care.

Additional cons:

  • Odours may build if worn repeatedly on multiday outings.
  • Potentially vulnerable to staining.
  • Petroleum-based fibre.


This almost always refers to merino wool, which is popular due to its soft “ultrafine” fibres. Many people are surprised to learn that lightweight (even “micro weight”) merino wool creates a terrific all-season base layer.

Additional pros:

  • Lightweight merino wool is soft on skin.
  • Usually machine-washable.
  • Stain- and wrinkle-resistant.
  • Natural fibre with a high comfort factor

Additional cons:

  • Typically available only in darker colours.
  • Potentially vulnerable to shrinkage.

What is Merino Wool?

Full wool Merino sheep.
Full wool Merino sheep. (Photo credit: Wikipedia)

The source of merino wool is merino sheep, a breed that originated centuries ago in Spain. (The word “merino” has Spanish roots.)

Merino sheep were introduced to Australia in 1794, and they flourished in the island nation’s temperate interior. Today the majority of merino sheep are raised in New Zealand (at high elevations), Australia, South Africa and South America where the climates and the vegetation consumed by sheep contribute to the exceptional quality of merino wool. It is estimated that 1 square inch of skin on a merino sheep produces roughly 4 times the number of fibres than other breeds.

As mentioned earlier, merino wool fibres range between 15 to 24 microns in diameter, with 17.5-micron fibres (rated “ultrafine”) often used for next-to-skin apparel. The merino industry regards 18.5 microns as the average fibre diameter most people can wear without experiencing an itchy sensation.

In comparison, human hair ranges between 18 and 180 microns, with an average diameter of about 60 microns. Only the wispiest, most flaxen human hair comes close to approximating the diameter of merino wool.

The abundant crimps in merino wool fibres permits the spinning of high bulk, resilient yarns, which can then be knitted or woven into structures tailored to particular end uses. For outdoor apparel and socks, knits are the most common structures.


Silk (Treated Silk)

Silk underwear is largely a specialty fabric, intended primarily for cool- and cold-weather usage. “Treated” indicates the silk has been chemically modified to enhance wicking (a fabric’s capacity for moving perspiration off skin to speed its evaporation). Fans of silk are strongly attracted to its smooth texture.

Additional pros:

  • Soft, luxurious texture.
  • Thin; adds no bulk and layers well.
  • Natural fibre.

Additional cons:

  • Some styles require hand-washing; machine washing sometimes causes shrinkage.
  • Potentially vulnerable to abrasion and sunlight.
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Wicking: Synthetic Fabrics

Wicking: Synthetic Fabrics

Capillary action also occurs with synthetic performance underwear. Here’s how:

  1. An active person wearing a polyester T-shirt begins to sweat.
  2. A high-humidity “microclimate” is created between the person’s sweating skin and the shirt covering the skin.
  3. Perspiration vapour and moisture condense on the garment’s interior (its underside).
  4. Because everything in nature moves toward equilibrium, the high-humidity air mass between skin and garment will seek a path to a lower-humidity environment. The difference (gradient) between temperature and humidity on both sides of the garment becomes the driving force that moves the warmer, wetter air beneath the garment toward the cooler, dryer air on the outside.
  5. Wicking takes place when perspiration moisture travels along the surface of the fibre but is not absorbed into the fibre. (Synthetic fibres are, essentially, plastic—and virtually non-absorbent). Moisture escapes to the outside through the interstitial spaces (the miniscule holes) between the knitted yarns.
  6. Moisture is dispersed across the fabric’s exterior, where it evaporates after contacting the lower-humidity environment outside the shirt.

Wicking is enhanced by:

Fabric construction:

  • Fibres with an altered texture (roughened or grooved) can transport moisture more quickly.
  • Fabrics such as Polartec PowerDry use a 2-sided “bi-component” construction. Such fabrics typically position thinner yarns closer to the skin (sometimes dotted with moisture-collecting “touch spots”) and place larger yarns on the garment’s exterior, providing more surface area for moisture dispersal and evaporation

Chemical treatments:

  • Some type of chemical finish is applied to nearly every synthetic fabric in order to boost wicking performance. The finish usually convey some degree of hydrophilic (water-attracting) attributes to polyester, allowing it to more speedily draw moisture along its non-absorbent fibres and transport it to the garment’s exterior.

Note: Polyester, while synthetic, does have a very small absorption rate, roughly 0.4% of its weight. (In contrast, cotton can absorb 7% of its weight.) Polyester’s absorption rate is so minimal that it is generally regarded as non-absorbent.

Wicking Magic of Wool

Superfine wool Merino ewes and lambs, Walcha, NSW.
Superfine wool Merino ewes and lambs, Walcha, NSW. (Photo credit: Wikipedia)

Wicking magic of Wool

Technically, it can be argued that wool does not wick moisture. The end result, however—fibres moving perspiration away from skin and dispersing it through evaporation—is the same.

Rather than straining perspiration moisture and vapour through the tiny, tiny gaps in a non-absorbent synthetic knit, wool’s inner core (cortex) absorbs moisture—between 27% and 36% of its weight.

This absorbed moisture is then impacted by the lower humidity, air movement and (potentially) sunlight on the outside of the garment. The result: evaporation.

With so much moisture being absorbed, will a wool garment feel soggy? If it becomes saturated and is confined to a damp or high-humidity environment, it could. (Synthetics are often a better choice for excursions where persistent rain is likely.)

Yet wool has the capacity to both absorb moisture (in a vaporous state such as perspiration) while also resisting water (in a liquid state such as light rain). This is one of the almost-too-good-to-be-true marvels of wool.

Wool fibres have a scaly exterior layer called the cuticle, and that is overlaid with the epicuticle, itself coated with lanolin, a waxy, water-shedding film. It is the epicuticle and its waxy coating that makes wool resistant to mist and light rain (hydrophobic). It is this hydrophobic layer that touches your skin, minimizing (or eliminating) any sensation of dampness.

A very sweaty person can overwhelm any fabric. During those moments a wool garment will likely feel less damp and clammy on your skin than a synthetic garment, but it may feel weightier. A synthetic garment will dry out and feel lighter more quickly.

As a total sweat machine myself, I have to laugh at enthusiastic promotional claims (“Keeps you dry!”) sometimes linked to wicking garments. If a T-shirt shut down my ability to sweat, I’d be worried. What wicking fabrics do is allow you to feel drier faster than if you were wearing cotton or some other nontechnical fabric—and that’s a huge positive that, in my mind, makes them worth the money.

Wool Texture and Temperature Regulation

Some people may be hesitant to consider wearing wool as a next-to-skin fabric.

Realize that performance underwear designed with wool uses merino wool, which consists of “ultrafine” fibres just 17.5 microns in width, fine enough that people will not experience the scratchy sensation often associated with traditional wool. The average human hair, just for comparison, measures 60 microns.

A property unique to wool is its ability to release small amounts of heat as it absorbs water. This effect is known by the arcane term “heat of sorption.” Energy, in the form of small amounts of heat, is produced through the work of moisture-absorption by wool fibres. Thus, in damp conditions, a wearer could potentially collect a small amount of comfort from this phenomenon. This is in addition to the countless warmth-trapping air pockets created by all the crimps inherent merino wool fibres.

Could that make wool too warm in hot conditions? Not necessarily. Evaporating moisture within the cortex can cool the air between the wool fabric and your skin, promoting a stable body temperature. Also, breathable wool fibres can buffer skin from air heated by the sun the same way they can trap warmed air and keep it close to skin in cool conditions.

Admittedly, these nuances can be tough to detect in the field, and when conditions turn seriously cold, you will obviously need more than a lightweight wool tee to maintain a comfortable body temperature.



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