Person wearing base layers outdoors

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 Label base layers: Peak Comfort line

MEC Peak Comfort base layers come in merino-blend or synthetic fabrics, each with its own benefits:

Close up of three different MEC base layer fabrics

Left to right: MEC Peak Comfort AirGrid Lite, AirGrid Warm, and Merino Warm fabrics.

AirGrid Lite

Great for: moisture management. A good warm weather go-to or base layer if you run hot.

  • Waffle knit keeps fabric off your body to allow air flow, and helps moisture evaporate when you sweat.
  • Durable odour treatment keeps you smelling fresh.
  • Lightweight, dries quickly and moves with you.
  • Bluesign-approved® fabric for sustainability.

AirGrid Warm

Great for: cold weather, high-output activities (think skinning up a steep backcountry slope).

  • 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.
  • Lightweight, packable, 4-way stretch.
  • Includes recycled content.

Merino Warm

Great for: extended days of activity, like cool-weather multi-day hikes.

  • Merino wool fibres are spun around a nylon core to give you all the benefits or merino, but with more durability.
  • Naturally odour resistant and temperature regulating.
  • 4-way stretch for all day comfort.
  • Responsible Wool Standard certified.

In terms of fit, Peak Comfort bottoms are a next-to-skin fit that’s made to contour your body. Tops are slim fitting with a low-profile silhouette for layering and movement.

Person wearing MEC Label base layers, sitting on a log outside holding a mug and looking happy

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.