A beginner's guide to understanding baselayers.
No matter the activity, adding a baselayer underneath your primary clothing can make a big impact on your experience. This article will go over the purpose of a baselayer, how to pick which fabric type is right for you, and how a baselayer should fit.
What is the Purpose of a Baselayer?
A baselayer is the layer of clothing closest to your skin. Sometimes referred to as "long underwear", baselayers are crucial in maintaining comfort outdoors by keeping you warm in the winter and cool in the summer. Good undergarments are incredibly helpful in maintaining temperature and in wicking moisture away from the surface of your skin. In addition to this, their ability to dry quickly means that you won't freeze when you sweat in the winter.
On stormy days, baselayers are crucial to increasing your comfort while wearing a rain jacket. For materials like Goretex to work, sweat needs to exit your rain shell in the form of vapor. If your sweat remains in a liquid state, it won't pass through the millions of tiny pores that make Gortex breathable. Without proper distribution of moisture and sweat, rain jackets and pants can become uncomfortable and even painful as wet clothing creates more friction, causing chaffing.
Baselayers are also great in warmer weather. Lighter baselayers can be used in summer, reducing the likelihood of chafing while keeping you cool. In the case of warmer temperatures, wicking keeps you dry and cool. Thinner fabrics pull water away from the skin through capillary action, taking excess body heat with it.
Baselayer Materials
For the most part, you will likely be deciding between synthetic or wool fabrics (or a hybrid that combines the two). Silk is the third option but is generally not recommended. While silk is known for its soft feel, it does a poor job at temperature regulation and is the least effective at wicking moisture away from the skin. In addition to this, silk is delicate, tends to retain odors, and should be washed after every use.
Synthetic baselayers excel at moisture wicking, are quick to dry, and are not as heavy when wet. Baselayers made of synthetic materials also tend to be less expensive and slightly more durable than their wool counterparts. One of the downsides of wearing synthetic clothing is its tendency to retain odors. While wool can go quite a while before needing a wash, synthetics will start to smell if worn too long. Some brands mitigate this (like Patagonia's Capilene Cool shirts) by treating the fabric in antimicrobial solutions, but the effects may fade over time with washing.
The other material to consider is wool, specifically, merino wool. Merino wool is softer than traditional wool because each individual strand is thinner. The overall texture can depend on the weave, but good manufacturers have their clothing woven in a fashion that reduces the number of ends (of individual strands) that stick out. Weave type can help reduce itch, but some brands like Smartwool also wash their wool in a way that reduces the oils that some people are allergic to. Wool is naturally odor-resistant and is great for multi-day trips because it doesn't need to be washed nearly as frequently as synthetics. Merino wool is also an excellent way to regulate body temperature performing well in warm and cold conditions. Wool generally performs well in regards to its moisture-wicking abilities, but its efficiency does depend somewhat on the weave used.
The disadvantages of wool come down, mostly, to cost. Merino wool can get expensive quickly, with Smartwool's midweight currently costing around $110 for a long sleeve top. Some report that their wool is less durable than synthetic layers, but in most cases, this seems to be caused by overwashing. If you wear your wool multiple times before washing, it will greatly expand the lifespan of your undergarment.
Why Cotton is Not an Option
The phrase "cotton kills" gets thrown around by outdoor enthusiasts often and may seem like an exaggeration to some, but cotton can become dangerous in the wrong conditions. When cotton gets wet, it stays wet. Cotton does not dry quickly. When dry, cotton insulates very well, but when it is wet, it loses its ability to retain heat entirely. Unlike wool, which will continue to insulate you when wet, cotton's insulation abilities are a result of air pockets formed within the fabric. When these pockets of air fill with water, they are useless. Cotton can hold a lot of water, making it exponentially heavier when wet. Because sweat and perspiration are produced in most activities, even a brisk walk, cotton's ability to become waterlogged is not looked upon favorably. If you are going to be exerting yourself in any way, cotton is not a good option. If you plan on going into any damp or wet environments (think mountains, rain, or high humidity areas) will result in uncomfortable or even dangerous conditions.
How Much Insulation do you Need?
Lightweight baselayers perform best in moderate or cool temperatures. Because they are thinner, they dry and wick moisture away from the skin faster than thicker baselayers. These characteristics make lightweight baselayers great for high-output activities like running or on a strenuous hike when you need sweat to be wicked away from your skin quickly.
Midweight baselayers are the most versatile as they do a good job at providing a significant amount of additional warmth while still maintaining decent moisture-wicking abilities. These baselayers are great for almost any occasion (excluding summers in most regions). Perfect for the shoulder seasons and a great layer for winter months.
Heavyweight baselayers are intended to be used in very cold conditions. If your activity involves you working up a sweat, this could be around the 0°F mark (around -17°C). If you are just taking a leisurely stroll around the neighborhood you might want to consider a heavyweight baselayer starting at temperatures below 32°F (0°C). Heavyweight baselayers are not usually designed with moisture-wicking in mind and a lightweight baselayer may be worn under the heavyweight to be more comfortable.
Finding the Right Fit
Baselayers need to be close-fitting to facilitate moisture wicking and to help with temperature regulation. Snug baselayers allow for better sweat-wicking, which is important when you are producing a lot of it. While you want your baselayers to remain very close to the skin, beware of overly tight baselayers. Too tight of a baselayer can result in restricted blood flow and will also limit your movement, especially at your joints. Your baselayer should be making consistent contact with your skin (think spandex) but not tight enough to be considered compression shorts. With higher output activities, it becomes more important to have a baselayer that fits well. Activities that require less effort can afford some wiggle room with sizing.
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