Choosing Thermal Underwear

Are Wool or Synthetic Base Layers Best for Mountain Sports?

New Zealand Merino Sheep  - Icebreaker
New Zealand Merino Sheep - Icebreaker
Next to the skin there's the option of wool, a natural fiber or, a synthetic such as Polypropylene recycled from soda bottles. The choice may be an environmental one.

Skin is the body's interface with the surroundings. In the mountains where conditions can be harsh - glaring heat and chilling cold - even in the same day the epidermis (skin), the body's largest organ, becomes even more significant. Controlling temperature and fluid loss (sweating) is critical to energy conservation.

Skin provides insulation and acts as a temperature regulator. Since mammalian skin doesn’t have sufficient hair density to be classed as fur; humans need to seek out additional sources of insulation for comfort and survival.

Cotton garments have long been considered inappropriate in the mountains. Once wet (e.g. from sweating) cotton stays wet and when the temperature drops it draws heat away from the body.

Recyclable Synthetic Underwear

Polypropylene – has that staunch bearded mountain-man persona as if to say “Of course I smell – I’m a real mountain man (/ woman)."' Yet 'polypro' as it is commonly known, is developing a new image - a social conscience. In this age of carbon footprints, 'polypro' is becoming an environmental garment of choice.

Polartec®, Polypropylene and Capilene® are among branded synthetic fabrics that can now be recycled.

It may well become commonplace for threadbare fleeces, singlets and long johns, at the term of their wearable life, to be broken down, purified and polymerized into the raw material of polyester chips ready to become the next generation of adventure garments.

Also in the ‘polypro’ line, led by Patagonia, is PCR® clothing - garments made from post consumer recycled plastic. In 13 years they claim to have spared landfills of 92 million plastic soda bottles. Learn more at Patagonia's website.

Pure Merino Wool

Wool is the main competitor in the adventure underwear trade. This stoic natural fiber, a far cry from its scratchy plaid and tweed days, is getting more sensuous and sophisticated by the minute. Only 140 grams per square meter at its silky, odorless, finest (e.g. a Superfine Icebreaker garment); wool can be delicate enough to swaddle a newborn infant.

These days merino thermal garments are equally at home in a backcountry hut, on a challenging desert trail, as a base layer part way up the cold face of a mountain or après-adventure teamed with some street-conscious jeans in the closest cocktail bar.

Icebreaker, the New Zealand-based leader in outdoor apparel was the first company in the world to develop a merino wool layering system.They are so particular about their raw material that they have developed an on-line 'Baacode' system. Customers can trace their pure merino garments through every step of the production process - right back to the New Zealand sheep station the wool came from.

The comment made by Jeremy Moon, founder and CEO of Icebreaker at a Rally in Salt Lake City in 2007, "When you're outdoors, does it make more sense to wrap yourself in something natural, or something plastic?", is very compelling.

Advantages of Wool Underwear

  • Natural fiber
  • Environmentally sustainable raw product - Keratin (protein based)
  • Fine merino wool blends can be worn directly against the skin without irritation
  • Stays warm when wet
  • Renowned for being odorless after weeks of use

Disadvantages of Wool Underwear

  • Fine merino varieties are expensive relative to their synthetic counterparts
  • Slow to dry
  • Short wearable life with rigorous use

Advantages of Synthetic Underwear

  • Typically cheaper than a natural fiber equivalent
  • Quick drying
  • Some products are recyclable
  • Long lasting

Disadvantages of Synthetic Underwear

  • Tendency to harbor odors
  • Can irritate the skin after sustained use
  • Origin of synthetic fibers is oil a carbon based non-renewable resource

There are many factors to take into account for the apparently simple task of choosing thermal underwear. It is becoming increasingly important for environmental concerns to play a part of this everyday decision making process.

Portrait of Lisa Auer, Bishop, California, Martin Svensson

Lisa Auer - Lisa currently shares her time between working as a mountain guide and as a 'word and web smith' as she likes to call herself. Based in ...

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