Selecting the Best Base Layers for Winter Outdoor Activities

The most important idea to take from this article is that you should layer clothing in winter if you are in low temperatures at around freezing or lower.  Layering clothing means that you wear several layers - usually 3 layers.   The first layer is the base layer or thermal long underwear layer.  I am sure everybody knows about long underwear from old west TV shows.  In the olden days this is what you wore in addition to the usual underwear as a layer under your pants to keep you a little warmer.  The olden days goes back to the old west where cowboys and even shop owners in Wyoming, South Dakota, and even Denver - wore Long Johns or Union Suits or some kind of layer of warm underwear - usually long underwear, next to the skin.

Today we can choose from thin silk layers, fleece or lofted expedition weight long underwear and many other fabric technical choices in-between.  We also have a choice of short sleeve, long sleeve, Zip-T, crewneck, mock turtleneck or turtleneck, shants, etc.  A Zip-T is a top with a half-zipper at the neck.  This allows you to unzip it and get additional ventilation when the temperature goes up.  In selecting from these choices consider whether the weather will remain cold all day long, or will there be a warm up.  If you expect a warm-up, wear a Zip-T for the flexibility that it gives, or a crewneck.  If you are in Antartica in the winter you would want a turtleneck all day and night.  In addition to the long legged base layer you may also want to choose from a technical warm underwear as well.  This would be a performance boxer or brief that is made from a  wicking polyester or some other type of fabric that does not promote clamminess from perspiration.  Fabrics that hold on to water result in chilling and discomfort from feeling cold.  Since you will wear clothing over the baselayer it is best to pick a fabric that is smooth on the outside so that you can easily slide on the next layer.  For extreme cold choose a fleece type base layer with a smooth outer surface.     

Fabric choices    

There are several good choices for the base layer fabric.  Wool:  Wool fibers have a waterproof outer layer that repels water.  This feature of wool also means that water is not held near the skin where it can cause chilling.  Wool does hold water and does not wick away moisture the way that man-made fibers do.  Moist wool is actually still able to insulate the body from cold because of the way moisture is held between the fibers. A lot of people still prefer wool or a wool blend for their thermals.  Historically wool was a popular choice for soldiers in WW II.  It is important to note that wool can shrink in the wash.  Merino wool base layers can be worn next to the skin without feeling the itch typical of wool.   Silk: Usually silk is worn as a thin layer.  I like silk as an additional layer and I sometimes have worn a 4th layer of silk in single digit weather.  Silk is smooth and this makes it easy to slip on a layer over it.   Buy silk fabric that is treated to improve its wicking capability.  If you are doing winter outdoor sports,  look for silk base layers knitted in the interlock pattern because this will improve its elasticity.  This is important if you will be active while outdoors in the cold.  Modern day silk is machine washable and a fairly easy care fabric.   Polyester and Polypropylene:  These fabrics dry fast and wick moisture away from the skin.   These fabrics hold their shape well which is important to reduce bunching when worn under other apparel.  Polyester and Polypropylene have good durability and hold up well to washing.  Hikers and backpackers prefer a polypropylene base layer because it keeps you warm and dry, but it weighs less than polyester. Compared to silk and wool polypropylene and polyester are easy care fabrics that can be washed in warm water.   These fabrics are among the best rated modern day fabrics for winter outdoor sports.   Polyester and Polypropylene are not naturally odor resistant fabrics.  However, look for odor resistant treatment in Hot Chillys base layers. 

Fabric Weights    

Heavyweight and Expedition Weight thermals usually have a lofted layer against the skin to trap heat for extra warmth.   Look for fabrics for your base layer shirt that are smooth on the outside for ease of on-off of the outer layer shirt.   Heavyweight fabrics may not be the best choice for extreme exercise even in moderately cold conditions because of the potential to overheat and because the fabric is more restrictive of your movement while engaging in extreme sports.
Midweight: Most choices for baselayers fall in the midweight range.  There are actually a wide range of thicknesses and fabric textures in the mid-weight range of base layers.   For you midweight base layer select the fabric based on your ability to handle cold and the expected temperature range.  Highly textured fabrics have the ability to trap heat and keep you warmer. Examples are waffle weave texture.   Some fabrics are thicker but smoother in texture.  These types tend to be Polyester or some other form of manmade fabric.  Look closely at the knit pattern to see if there are air spaces within the fabric of the base layer that can trap air.  These can be smooth and easy to put on or off and also to slip another layer over the base layer, but still able to trap air to retain warmth.
Lightweight: Lightweight base layers are good for extreme exercise in moderately cold temperatures or as an additional layer.  They are also good for more sedentary activities at about the freezing level.  This would include ice fishing, walking and football games.

Other Technical Features

Some base layers have zones or panels that provide extra stretch or ventilation.  Some highly technical base layer products have zones of Heavyweight fabric and zones of lightweight fabric in areas that are high heat output areas such as the armpits.  If you look at a highly technical base layer you will see that there are usually panels around the shoulders and side-waist that allow the garment to be more form-fitting to eliminate bunching and improve your ability to move while doing extreme sports.  This type of base layer would be particularly useful as skiing base layers.
At Overland Trails we have a large assortment of Base Layer types.  Many of our base layers are highly technical at liquidation prices, that are not expensive in price but are and are not cheap base layers - they are very high quality made by such well-known brands as Hot Chillys and Coldpruf.  These high performance base layer s are very good choices for extreme outdoor activities in cold conditions.   

Selecting the Best Base Layer For Your Activity

There are specialized base layers for every sport.  You can choose from  running base layers, ski base layer, snowboard base layer.  Each is a little different in the location and  capability of stretch panels, padding etc.  A running base layer can have additional evaporation panels in high heat areas.