This is the against the skin layer. The key here is moisture management – fabric should wick moisture away from the skin to keep you dry and warm. Base layers range from briefs and sports bras to thick long underwear sets1.
The mid layer is the insulating layer, meant to trap heat against the body and provide warmth from low temperatures. Fleece is the most common fabric for mid layer garments2. Mid layer garments should provide warmth without too much bulk.
Your outer layer, or shell, is your weather protection. Depending on your activity, these should be wind-tight, waterproof, and provide additional insulation if necessary. One of the more important factors of the outer shell is that it is breathable – moisture needs to be able to escape from the base and mid layers through the outer layer.
Beyond the Basics
With the wide ranging fabrics and differing garment types available in each layer category, it is possible to create a wide range of combinations to best suit your needs. Sometimes you will need the heaviest of all three layers, other times a light base layer and mid layer vest will do. These are the factors to consider when choosing your layers.
Fabric is the most important consideration here. If you’ll be moving frequently and sweating, or in a damp or wet environment, cotton should be avoided as it retains moisture. Instead, choose fabrics designed to wick moisture away from the skin to evaporate. Activity level is also important for determining how warm you need your base layer to be. Stationary activity – like driving a forklift or ice fishing – means you want a long underwear set, with a lining for extra comfort and warmth. Hiking in mild temperatures likely only needs a long, moisture-wicking shirt. And don’t forget – base layers aren’t just for your upper body; your lower half needs protection too.
Base Layer Examples
The mid-layer is your primary insulation layer. It is meant to trap heat against the body, providing warmth and protection from low temperatures. Keeping your core warm is essential to overall body warmth – the warmer your core is, the more blood gets to your extremities. Vests are versatile layer addition for a range of temperatures and activities to keep your core warm while retaining a full range of motion for your arms. Fleece is often used in warmer environments or with more active duties; insulated vests or jackets are better suited for colder environments or more sedentary duties.
Mid Layer Examples
The outer layer provides protection from the elements – wind, water, and extreme low temperatures. In windy outdoor conditions, or job duties like operating equipment that creates a wind stream, your outer layer needs to be wind tight to prevent the additional chill from reaching you. In rainy conditions, or job duties that mean frequent contact with condensation, your outer layer needs to be waterproof. Remember – moisture is the enemy of warmth. In extreme low temperatures, the outer layer should also provide extra insulation.
Outer Layer Examples
Don’t forget about gloves, hats, socks, footwear and more to protect those areas that your jackets and pants don’t cover. Check out our “How to Choose the Right Gloves” guide for tips on picking the right gloves for your activity and environment.
Down to a Science
You won’t always need all three layers, and sometimes you’ll need more than 3. Often, the waterproof outer layer can be stored until needed, or a mid-layer removed as the temperature rises throughout the day. The more you experiment, the better you’ll be at choosing the right layers for differing duties and activities. What is important is to consider not just the temperature, but your activity, the environment, and how the material of each of your layers works in those conditions.
- “Layering Basics.” https://www.rei.com/learn/expert-advice/layering-basics.html
- “Layering.” http://www.sierratradingpost.com/lp2/layering-guide/
- Kirsten Hostetter. “How Do I Layer for Cold Weather?” http://www.backpacker.com/gear/experts/ask-kristin/how-do-i-layer-for-cold-weather/