Smartwool Classic Thermal Review | CleverHiker

Bottom Line

From hiking in the Rockies to snuggling up in a cozy car camp, we tested the Smartwool Classic Thermal‘s breathability, warmth, comfort, and more. This layer is one of the warmest base layers we wore and a must-have for fans of merino wool.

When other base layers are too lightweight, this one provides the extra warmth you need. It also allows you to reduce the number of additional layers and thus bulk.

The merino doesn’t disappoint with its natural moisture-wicking qualities and its ability to fight off odors, making it perfect for multi-day wear. The wool is softer than one might think, and the seams are thoughtfully designed to be unobtrusive. The simple, no-frills crew neck design is a classic, and it comes in a ton of colorways to accommodate everyone’s style.

The torso fits a bit snugly, causing the layer to bunch up with heavy activity, but the extended cut gives you plenty of material to tuck into your pants and mitigate the bunch.  We also would have loved to see some thumb holes.

Comfort

When people think of wool, sometimes they think itchy, scratchy, and uncomfortable, but the material of the Classic Thermal is quite the opposite. It is very soft against the skin, even right out of the packaging.

Smartwool has used flatlock seams to avoid chafing and shoulder panels to eliminate top shoulder seams. This means reduced friction from backpack straps and other gear and virtually unnoticeable seams throughout.

The Classic Thermal fit is a little more snug than most other base layers, especially in the torso area. The torso is also longer than usual to aid in tucking the shirt in. We found that, when layered underneath other garments and doing some exercises, the Classic Thermal had a tendency to bunch up and “wedgie.” If this is a concern for you, or if you prefer a more relaxed fit, we recommend sizing up.

Warmth

The Smartwool Classic Thermal is a cold weather base layer. It’s likely too much for the warm months or even spring skiing in some climates. The snug fit of this base layer traps heat efficiently, and the wicking keeps cold moisture away from your skin. 

For the most frigid days, the Classic Thermal provides the extra warmth you need. Instead of adding another insulating layer, it’s much easier and less cumbersome to simply swap out your thin base layer with this one. The Classic Thermal is even warm enough to wear as a standalone layer when the day heats up, increasing versatility.

We even love this layer as a sleep shirt when nighttime temperatures dip on summer backpacking trips, but we wouldn’t use it as an active layer in warm weather.

Breathability

The Smartwool Classic Thermal is not the most breathable base layer of the base layers we tested. The tight, interlock knit fabric is made to trap heat rather than be super breathable.

While the wool naturally wicks moisture well, the lack of breathability increases its drying time. In our controlled lab testing environment, the Classic Thermal took the longest to dry.

The lack of breathability might be a plus, depending on your usage. For example, when worn as a standalone base layer in cold, windy weather, it feels warmer and cozier than most others, delaying the need to add a wind shell.

Versatility

The Smartwool Classic Thermal is a base layer targeted for cold weather, so it doesn’t have as wide a range of uses as some of the others. However, it will stick with you all winter long.

We love that this layer keeps us warm underneath our coat when we’re standing still and is an extra warm standalone layer when we get moving. The thermoregulation of the merino wool in conjunction with the slim, athletic fit, makes it ideal for ski touring or long winter hikes. It even keeps you warm when the wind picks up. Wool’s antimicrobial properties decrease odors, making the Classic Thermal ideal for multi-day camping trips. No one likes the chilling experience of changing their base layers in the wilderness in the dead of winter.

There are better options for shoulder season and summer use, but if you’re looking for something to use all winter long and reduce layers and bulk, the Classic Thermal is an excellent choice.

Style

Although the design is simple, the Smartwool Classic Thermal comes in an incredible 24 different colorways to fit your style. Dark, light, earth tones, stripes, heather, paneling, prints – Smartwool has offered this base layer in just about every style you can imagine. They have even recently updated the Classic Thermal with new colors and a new fit to enhance aesthetics. This layer can tend to run a bit on the snug side, so again, consider sizing up for a more relaxed fit. The extended torso adds extra coverage, but if you’re not tucking it in, it will bunch up at your waist, looking a bit odd.

Given its myriad of designs and updated fit, we wouldn’t feel ashamed to wear the Classic Thermal to a hibachi dinner.

Should You Buy the Smartwool Classic Thermal?

If you’re a big fan of merino wool and you’re looking for a warmer base layer to add to your layering arsenal, the Smartwool Classic Thermal could be the perfect choice.

It gives you the extra warmth you need when temps plummet and is even a cozy standalone layer with decent wind blockage when you need to let off some steam. Although it’s not the most breathable base layer, it still benefits from the natural moisture-wicking, thermoregulating, and odor-resistant qualities of merino wool and achieves what it was designed to do.

It’s soft and comfy with a thoughtful design from the seams down to the fit. If you like a more relaxed drape, be aware that the Classic Thermal features a snug, athletic fit, so you might consider sizing up.

Because of its targeted usage and admittedly steep price tag, we wouldn’t recommend the Classic Thermal for a single, do-it-all base layer. For that, there are more versatile options.

What Other Base Layers Should You Consider?

Smartwool Classic All-Season Review: The All-Season is Smartwool’s lighter, more breathable, and more year-round option. It is still mostly merino wool, but it has a friendlier price tag.

Arc’teryx Rho Heavyweight Zip Neck Review: This is the warmest base layer we tested for cold weather. It’s also very stylish and can easily be used as a mid-layer. 

Ortovox 185 Merino Rock’n’Wool Review: The Rock’n’Wool is similar in warmth to the Classic Thermal but with a touch more breathability and comfort. The style is unique, however, and doesn’t offer as many color options.