Person putting on ski jacket over baselayer, with mountains behind

How to choose base layers

Merino wool and synthetic base layers offer a wide range of benefits over typical activewear leggings, tights or cotton tees, and are far more versatile than your typical winter long johns.

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

MEC carries a variety of these versatile pieces from Helly Hansen, Patagonia, Smartwool and more, as well as MEC-label base layers. Each fabric has an individual weight, 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.
  • Fabric weight: MEC-label base layers come in three weights, from ultralight to expedition.
  • Local and seasonal weather: Knowing where and when you’ll need them narrows your scope.
  • Your favourite activities: You want a fabric and weight that can adapt to your needs, whether you’re hiking or travelling.

Merino wool vs. synthetic base layers

Base layers at MEC fall into two fabric categories: responsibly-sourced merino wool and a synthetic blend. The type of fabric you choose depends largely on your personal preference, as well as climate, activity level and desired amount of warmth.

Merino wool base layers

Merino wool is a renewable, natural fabric that moves and stretches with your body, so it won’t bag out. It has a finer gauge than regular wool, which means it won’t itch and will stay comfortable against your skin all day long.

Merino wool can absorb up to 30% of its own weight in water before it starts to feel wet. Even when it does get wet, it keeps you warm, so you never have that chilled feeling you’d get when wearing wet cotton. Merino wool is naturally antimicrobial, which reduces odours – perfect for travelling or multi-day camping trips.

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

Synthetic base layers

High-performance polyester or polypropylene fabrics wick sweat, absorb very little water and dry quickly with your body heat. Synthetic base layers get antimicrobial treatments to cut down on unwanted odours. They’re highly durable and feel slinky against your skin.

In addition, synthetic fabrics often have a UPF rating for extra UVA/UVB sun protection. These garments are usually more budget-friendly than merino wool options.

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

Blended merino wool and synthetic base layers

Some base layers are a blend of merino wool and synthetic fabrics. These options are the closest you can get to a one-size-fits all base layer, and they’re a good option if you’re short on closet or backpack space. They’re also more durable than full merino wool layers and can withstand lots of activity.

MEC base layer fabric weights

Within each fabric category – merino wool or synthetic – MEC-label base layers come in lightweight, midweight and expedition weight, so you can tailor your layering system for all conditions. The “T” in each weight’s name stands for “thermal.”

Most of the MEC-label products that include wool, including base layers, use merino wool. MEC-label synthetic layers are made from polyester and recycled polyester, and have 4-way stretch woven in for lots of movement.

MEC base layers for men and women

MEC synthetic base layers also give you the option for patterns and prints.

T1 base layers

MEC T1 base layers are our lightweight option. Similar to a tech tee, T1s are more for moisture management than warmth, although they’re a great option if you run hot. A T1 base layer is a great summer go-to. You can even use your T1 synthetic long-sleeve as a sun shirt.

T2 base layers

Our T2 base layers are a midweight and are warmer than T1 pieces. They’re a great option if you just want one versatile layer for all seasons and all activities. T2 pieces are well-suited to fall, winter and spring outings or cool summer nights.

T3 base layers

A MEC T3 layer is the equivalent of a lightweight fleece. These pieces are actually a slightly lighter weight (lower gsm) than our T2 layers, but they’ll keep you warmer, thanks to a high-efficiency grid (aka waffle knit) that traps air more efficiently without weighing you down.

Local climate and seasons

Where and when you plan on getting outside are key to your base layer choices. You might want to clock in a ton of ski days at Mont-Tremblant this winter, camp all over Ontario from spring to fall, or send BC’s Skaha Bluffs all summer. Travelling abroad adds a bit of 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.

Downhill skiers on a run near a chairlift

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 a T3 unless you’re in freezing conditions. If you’re always cold, a heavier weight will help you stay toasty.

T2 and T3 merino wool or synthetic base layers are great cool- and cold-weather options because they have more insulation and heat-trapping properties. Conversely, lightweight layers are great for hot weather; synthetics will wick sweat and dry quickly, while merino’s water retention properties make it a great choice for summer activities, since absorbed water can help keep you cool.

Base layers for different activities

Two trail runners on a path

Are you always trying the latest fitness craze, going from obstacle course races to Crossfit classes? Do you like to focus on endurance, going on long hikes or runs? Maybe you’re a relaxed but avid traveller or car camper. How you like to get outside is key to your base layer choices.

While the material you choose will largely be based on personal preference, some fabrics and weights are better for certain activities:

Relaxed and low-output activities

We recommend merino layers for times when you won’t work up much of a sweat – think travel, relaxed day hikes, downhill skiing, camping, urban cycling, grabbing some après bites, 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, sweaty bike commutes, and intense summer frisbee or soccer sessions. Put these layers through your toughest sweat sessions and multi-day adventures (they dry quickly, so you can wash them midway through your trip).