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Go beyond long johns. Base layers are the core of your active closet.

How to choose base layers

Merino wool, synthetic, and merino-blend base layers are far more versatile than your typical winter long johns.

Think of base layers as the core of your active closet. While they’re great for chilly-weather activities, you can use these tops and bottoms for hiking, climbing, camping, running, training or travelling all year long. A great base layer wicks moisture and keeps you warm during any activity.

Base layers come in different fabrics with different weights, which is measured in grams per square metre (gsm). The larger the number, the heavier and thicker the garment – although where base layers are concerned, heavier/thicker does not always mean warmer.

When you’re choosing base layers, here are some things to consider:

  • Merino wool or synthetic: These insulating fabrics work in different ways.
  • Activity output: You want a fabric and weight that can adapt to your needs and how hard you’re working.
  • Weather conditions: Knowing where and when you’ll need them narrows your scope.

Merino wool, synthetic or merino blend fabrics

The type of fabric you choose depends a lot on your activity level and desired amount of warmth.

Synthetic base layers

High-performance polyester or polypropylene fabrics wick sweat and absorb very little water. They also:

  • Dry quickly with your body heat.
  • Are highly durable and usually more budget-friendly than merino wool options.
  • Have antimicrobial treatments to cut down on odours.
  • Often have a UPF rating for extra UVA/UVB sun protection.

Most synthetic base layers are dryer-safe, but we recommend washing in cold water and hanging to dry to extend their lives.

Merino wool base layers

Merino wool is a renewable, natural fabric that moves and stretches with your body. It also:

  • Has a finer gauge than regular wool, which means it won’t itch against your skin.
  • Is naturally antimicrobial, which reduces odours – perfect for travelling or multi-day camping trips.
  • Can absorb up to 30% of its own weight in water before it starts to feel wet. A great choice for summer activities, since absorbed water can help keep you cool.

To help your merino wool layers last, wash and dry with care. We recommend a cold-water wash and laying flat to dry.

Merino wool and synthetic blend

A blend of merino wool and synthetic fabrics is the closest you can get to a one-size-fits all base layer. A merino-synthetic blend:

  • Is generally more durable than full merino wool layers.
  • Can withstand lots of activity.
  • Is good if you’re short on closet or backpack space, since you get the best of both worlds in one item.

MEC base layering system

We’ve got base layers down to a T. Our thermal warmth rating system is here to help you choose the right layer with ease. It’s easy – the higher the number, the warmer the base layer.

Cool T0

Super lightweight and sweat-wicking for working hard.

  • Lightest weight for high exertion or the foundation in your layering system.
  • Recycled polyester is bluesign®-approved.
  • Believe it or not, the fabric is made with coffee grounds for naturally antimicrobial properties. The coffee grounds constantly absorb odors and even reflect UV rays! Read more about Singtex® coffee mill.
  • Ideal for: running, cycling or any high-energy activity where you’ll be working up a big sweat. A great option for warmer weather or sunny days as well.

Warm T1

Temp-regulating merino-blend for high output activities.

  • Keeps you warm when temps drop and cool in warmer seasons.
  • Moves moisture away for quick-drying comfort.
  • Recycled polyester is bluesign®-approved, merino wool is responsibly sourced.
  • Ideal for: cross-country skiing, running or cycling – basically any activity where you’ll be on the move, but wanting a little more warmth.

Warmer T2

Mid-weight and moisture-wicking for all kinds of activities. Merino-blend or synthetic options.

  • Slim fit for easy layering.
  • Grid construction is kind of genius: air in the gaps act as an insulator to keep you warm without being bulky.
  • Grid also improves wicking, since moisture doesn’t stay trapped against your skin.
  • Recycled polyester is bluesign®-approved, merino wool is responsibly sourced.
  • Ideal for: cross-country skiing, backcountry skiing, snowshoeing. This is your warmth all-rounder, a match for most activities and perfect for piling on multiple layers.

Warmest T3

Expedition-grade warmth when it matters most. Merino-blend or synthetic options.

  • Made for high exertion in harsh conditions.
  • Moves sweat away from the body to chase away chills.
  • Keeps you warm during downtime.
  • Grid construction is kind of genius: air in the gaps act as an insulator to keep you warm without being bulky.
  • Grid also improves wicking, since moisture doesn’t stay trapped against your skin.
  • Made with responsibly sourced merino wool and recycled polyester.
  • Ideal for: winter camping, trekking, ice climbing. If you’re venturing into deep freeze temps where you’ll be standing still or exposed to the elements for longer periods of time, then this base layer is your best bet.

Activity output and base layers

How you like to get outside is key to your base layer choices. Do you like sweaty hikes and steep ski trips? Maybe you’re a relaxed traveller or car camper? While the material you choose will largely be based on personal preference, some fabrics are better for certain activities:

Relaxed and low-output activities

We recommend merino or merino-blend layers for times when you won’t work up much of a sweat – think travel, relaxed day hikes, downhill skiing, camping, urban cycling, staying cozy in your sleeping bag, or just hanging out. They’ll keep you warm and comfortable all day long. Merino base layers are even great as everyday T-shirts or winter pajamas.

High-energy, high-output activities

Grab synthetic base layers for moderate- to high-output activities such as brisk hikes, indoor or outdoor climbing, running, backcountry and cross-country skiing, or sweaty bike commutes. Put these layers through your toughest sweat sessions and multi-day adventures (they dry quickly, so you can wash them midway through your trip).

Weather conditions

Where and when you plan on getting outside are key to your base layer choices. Typically, the colder the average temperature, the higher warmth factor you should go for. Be sure to factor in your internal body temp as well – if you run hot, you probably won’t need the warmest weight unless you’re in freezing conditions. If you’re always cold, a heavier weight will help you stay toasty. Travelling adds a twist to choosing base layers, since you’ll want to go with what’s best for your destination’s season while saving on luggage space.