How to Choose Thermal Underwear for Cold-Weather Days

Shannon Prosser

Store Manager

A note from the author

We built this guide around the thermal underwear we sell at 162 Old Garden River Road, so every product named in it is one you can buy from us. Prices are shown as they were on our store the day this went up. If you have questions about fabric, fit, or layering, call us or come in and we'll help you sort it out.

Health Canada's Advice Starts With Layers, and Thermal Underwear Is the First One

Thermal underwear is the layer that sits closest to your skin, so it sets how the rest of your outfit behaves. The Government of Canada's Extreme cold page is a Health Canada "It's Your Health" document, written to help Canadians stay safe in severe winter weather. It makes three points that shape how we choose thermal underwear.

First, it says to dress in layers with a wind resistant outer layer, so you can remove a layer if you get too warm before you start sweating or add one if you get cold. Second, it says synthetic and wool fabrics provide better insulation, and that some synthetics are designed to keep perspiration away from your body. Third, it says that if you get wet, you should change into dry clothing as soon as possible, because you lose heat faster when you're wet.

Put together, those three points describe the job of thermal underwear: keep warm air close to your body, and manage moisture so that the warmth lasts. Everything below, from fabric to weight to fit, comes back to that job. Our men's base layers live in one aisle, so you can browse men's base layers and socks while you read.

Wool, Synthetic, or Silk: The Fabric Decides How It Behaves on a Long Day

Most shoppers ask about fabric first, and for good reason. Health Canada names wool and synthetics as the better insulators, so we'd start there. Here is how the thermal underwear on our shelves breaks down.

• Merino wool: Natural fibre, warm as a base layer, and the choice when you want the warmth to come from the fabric itself.
• Wool blends: A mix of merino and polyester that trades some of the pure-wool feel for a lower price.
• Cotton and polyester knits: A lighter, lower-cost thermal layer for days when you're not working hard.

Silk is the third fabric people ask about. We aren't going to make claims about it here, because we have no silk piece we can describe from our own product pages. Ask us in the store if silk is what you're after, and we'll tell you what we have on hand and what we don't.

Our take: If you can only buy one piece, make it wool or a wool blend. It matches what Health Canada recommends, and every Stanfield's piece below is made in Canada.

Pure Merino Is the Warmest Simple Choice We Carry

If you want one base layer that can also pass as a casual shirt, start with merino. The Stanfield's Men's Merino Wool Base Layer Top ($119.95) is a long sleeve crew neck in 100% merino wool jersey, made with yarns from New Zealand. It has full length set-in sleeves and a two needle hem on the sleeves and bottom, and it's made in Canada.

The matching Stanfield's Men's Merino Wool Base Layer Bottoms ($119.95) are the same 100% merino jersey, with a full length leg and a two needle hem at the bottom "for maximum warmth," as the product page puts it. Both come in black, in sizes S to 2XL, though stock varies by size, so check the product page for your size before you drive over.

Together the set is $239.90. That's the most we'd spend on a single set of thermal underwear, and it makes sense for people who wear it often: ice fishing, snowshoeing, winter work outdoors, or a long season of cold mornings in the Sault. Wearing it only a handful of times a year? Look at the next section instead.

A Two-Layer Wool Blend Gives You Warmth at About Half the Price

Stanfield's two-layer knit is the one we'd point a first-time buyer to. The fabric is built in two layers, and the space between the layers traps warm air from your body. The inner layer is 50% cotton and 50% polyester, chosen for absorbency and softness, and the outer layer is 50% merino wool and 50% polyester, chosen for warmth and strength. The garments carry an anti-microbial treatment.

The Two Layer Wool Blend Base Layer Top ($69.95) is a crew neck with long sleeves, set-in sleeves with rib cuffs, and taped neck and shoulder seams. The Two Layer Wool Blend Base Layer Bottoms ($69.95) add a full, roomy seat and a plush elastic waistband. Both are made in Canada and come in charcoal, in sizes S to 2XL.

A top and bottoms together come to $139.90, which is $100 less than the pure merino set. Our take: This is the best value in the aisle. You give up the all-merino fabric, and you get a thermal set that most people can afford to own two of.

One Piece Instead of Two

The Stanfield's Men's Two Layer Wool Onesie ($129.95) is a union suit, meaning top and bottoms in one garment, made from the same two-layer knit. Its overall fabric is 50% polyester, 25% cotton, and 25% merino wool. It has set-in sleeves with rib cuffs, a full button front, and a back trap door with a button closure for bathroom breaks.

Stanfield's describes it as one of the warmest garments you can wear next to your skin. It comes in charcoal and red, in sizes M to 2XL. We'd choose it for stationary cold, such as sitting on the ice or in a deer stand, where there's no waistband gap to worry about. It's $129.95, roughly half the price of the pure merino set.

A Waffle Knit Shirt Is the Light, Low-Cost Option for Moderate Cold

The Stanfield's Men's Waffle Knit Base Layer Shirt ($39.95) uses a waffle texture to trap pockets of warm air, and Stanfield's calls it a good thermal layer for moderate to very cold weather. It's 50% cotton and 50% polyester, made in Canada, in charcoal mix, in sizes S to XXXL.

It's the entry point, and we're happy to say so. Health Canada's advice is that wool and synthetics insulate better, and that you lose heat faster when you're wet. A cotton blend takes on moisture, so we'd choose the waffle knit for dry, low-effort days and move up to wool when you plan to sweat.

Weight Matters: Heavyweight Is a Middle Layer, Not an Underwear Layer

Thermal underwear comes in a range of weights, and the heaviest pieces shouldn't be your first layer. A good example is the Stanfield's Men's Heritage Fleece Lined Heavy Weight Wool Henley ($189.95). The outside is an 80% wool, 20% nylon heavy weight rib knit, and the inside is 100% moisture management fleece, with a three button placket and a made in Canada label.

Stanfield's lined it with fleece so that you don't need an extra garment under it, which makes it a warm shirt on its own rather than a base layer. It comes in alpine green, black, grey, and purple leaf, in sizes XS to 2XL. One note from the product page matters: This garment shrinks because of its fibres. The sizing allows for it, so buy your normal size and follow the washing instructions.

So how do you choose a weight? Think about how you'll spend the day.

• Moving all day (snowshoeing, shovelling, hauling gear): A lighter wool or the waffle knit, so you don't overheat before you start sweating.
• Standing or sitting still (ice fishing, hunting from a stand): The two-layer knit, the merino set, or the onesie.
• Everyday winter wear: The two-layer set, with a heavier shirt such as the henley on top.

How to Layer on Top: Base Layer, Then Insulation, Then a Wind Resistant Shell

Health Canada's layering advice is short: dress in layers, with a wind resistant outer layer. Applied to a day outside, that looks like this.

1. Base layer: Your thermal underwear, worn next to the skin.
2. Middle layer: A heavier wool or fleece piece, such as the henley above.
3. Outer layer: A wind resistant shell, which you can open or remove before you start to sweat.

Add warm socks, gloves, and a hat, which the same page lists as part of dressing for cold. For socks, the Darn Tough Men's Over-the-Calf Midweight Hunting Socks ($44.95) are 59% merino wool, 38% nylon, and 3% elastane. They reach just below the knee, so they cover the shin and leave little bare leg between your boot and your bottoms.

The layer most people skip is the one that comes off. Health Canada says to remove a layer before you start sweating, because wet clothing loses heat faster. Take off the shell first, then open the middle layer, and keep the thermal underwear on.

Fit and Care Keep Thermal Underwear Working

Thermal underwear works by holding warm air close to your body, so it should fit snugly without squeezing. A loose top bunches under your jacket, and a tight pair of bottoms can restrict movement at the knee. If you're between sizes, the product pages list the sizes we carry, and we can help you in the store.

Check the care instructions on each product page or garment label before you wash anything. The henley's note about shrinkage is the clearest example, and wool in general is worth treating with the same care. The Darn Tough socks, for their part, are listed as machine wash cold on gentle, inside out, and tumble dry low or hang dry.

Questions

Wool, synthetic, or silk?

Health Canada says synthetic and wool fabrics provide better insulation, so we'd start with wool or a wool blend. Merino is our warmest simple choice, and a blend such as Stanfield's two-layer knit costs less. Synthetics can help move perspiration away from your skin. Ask us in the store about silk, since we have no silk product page to point you to.

How do I layer on top?

Wear thermal underwear next to the skin, add an insulating middle layer such as a heavier wool shirt or fleece, and finish with a wind resistant outer layer, as Health Canada recommends. Choose pieces you can remove one at a time, and take a layer off before you start to sweat. Add warm socks, gloves, and a hat to finish the outfit.

Do I wear it directly on skin?

Yes. A base layer is made to sit next to your skin, which is how it traps warm air and manages moisture. Stanfield's describes its two-layer knit as keeping warm air close to your body, and its onesie as one of the warmest garments you can wear next to the skin. Whether you add regular underwear below is a comfort choice.

Come See Thermal Underwear at Our Store in Sault Ste. Marie

The easiest way to choose thermal underwear is to feel the fabrics side by side and try on a size. Visit Great Lakes Outfitters at 162 Old Garden River Rd, Sault Ste. Marie, ON P6B 5A6, or call us at (705) 253-2361, and tell us what your cold-weather days look like so we can match you to the right set.

Talk to us about it

• 162 Old Garden River Rd, Sault Ste. Marie, ON P6B 5A6
• (705) 253-2361
• Open today 10 a.m. to 6 p.m.
• Send us a message

References

• Government of Canada, Health Canada: Extreme cold (It's Your Health)

About the author

Shannon Prosser

Store Manager

I have been here three years. Before that, I worked for Moore's Clothing and Charm Diamond. I manage the store. Come to me for clothing and footwear: Outdoor Research, The North Face, Columbia, Kuhl, and all of our footwear.

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