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In winter, when it’s cold, it’s better to dress in layers like an “onion,” meaning layering multiple pieces of clothing. Start with a base layer. I know that many of you use Heat Tech from Uniqlo, but I don’t recommend it because it traps sweat and heat, making it uncomfortable. For me, the best solution is merino wool. Some people also use base layers made of cashmere and silk or merino wool and silk, but those options tend to be pricier.
Merino wool comes from merino sheep, which are hardy animals capable of withstanding both harsh winters and sweltering summers. Their wool is exceptionally fine and tear-resistant. Additionally, it offers excellent properties: thermal insulation, moisture management, anti-static, odor resistance, lightweight, quick-drying, and wrinkle resistance—all ideal qualities for a winter base layer. This is particularly useful for those who might sweat and feel hot in the Parisian metro, then freeze as soon as they step outside.
The main difference between cheap merino wool and high-quality merino wool lies in the fiber diameter. Unfortunately, manufacturers don’t always disclose this. Fibers can go as fine as 9-12 microns (rarer and more precious than cashmere), but a diameter of 19 microns is already excellent. The finer the fiber, the less it irritates the skin, which is why merino wool feels pleasant even in summer. Some brands add silk, cashmere, or offer virgin merino wool (the first shearing of the sheep, rare and precious). All of these factors influence the price. However, a higher price doesn’t always mean better quality, so research before purchasing.
I recommend having at least two pieces: one with short sleeves and one with long sleeves, depending on the weather.
Here are my two favorite brands:
Icebreaker
During my world tour, I only wore merino wool t-shirts all year round. My favorite brand is Icebreaker, a well-known New Zealand brand among trekkers and globe-trotters.
In winter, my favorite base layer is this hoodie from Icebreaker, with an integrated hood and mittens. Reference: Icebreaker Merino Women’s Luxe Rib Pullover Hoody, which cost 100 euros at the time. Unfortunately, it’s no longer available for purchase. Buying from Icebreaker ensures the origin of the fiber: New Zealand. If you’ve been to New Zealand, you’ll agree with me that the sheep there are probably the happiest in the world, having all that space to roam. The high price reflects the brand’s reputation.
I’ve had it for 6 years now, and apart from a small hole I can repair with embroidery (this hoodie has been terribly mistreated since I sent it to any dry cleaner and ignored washing instructions), it has fully satisfied me. The major difference between a cheap brand and a quality brand lies here: You can afford to mistreat merino wool (everyone occasionally mixes merino wool with jeans in the wash, for example), and this piece has proven to be very durable.
However, its look is a bit casual due to the hood, so it can’t be discreetly worn under a shirt, for instance.
In 2025, you can choose these alternative products, which are easier to wear as a base layer. They’re not identical to mine but are also 100% merino wool. With a fiber diameter of 19 microns, they are of very high-quality merino wool.
Note: I know many people buy from Ortovox. JB had a few t-shirts from Ortovox, but they tore much faster than Icebreaker products.
Hanro
Hanro is a luxurious Swiss brand known for its undergarments made from natural materials such as cotton, linen, wool (merino, cashmere), and silk. Worn by icons like Marilyn Monroe and Nicole Kidman, Hanro now manufactures base layers, loungewear, nightwear—everything lightweight yet warm and/or comfortable.
They have an outlet in Portugal where they sell garments with minor imperfections. On Vinted, I found a seller near the outlet who resells these new items on Vinted at an attractive price (around €20–€25 per piece). The imperfections are indicated in the listing (usually minimal and related to weaving defects). Sure, she makes a profit at that price, but it saves me a trip to Portugal. I chose this V-neck t-shirt, 70% merino wool, 30% silk, in a dark color.
Hanro is experienced in making undershirts to wear beneath formal shirts, so they pay great attention to ensuring these layers remain completely unnoticeable. For example, the sides are seamless, and the armholes, sleeves, and hem have ultra-flat finishes. This ensures that the seams not only don’t irritate the skin but also won’t show under outer layers. If you’re wearing a very tight dress or a flowy blouse, this layer acts as a second skin and is completely invisible.
I chose a dark color, so the t-shirt doesn’t seem transparent to me, but I’m not sure what it would look like in a cream color.
However, I found a small defect at the bottom of the t-shirt, but this is probably why it didn’t pass the quality control.
From Hanro, I also purchased leggings made of 65% silk and 35% cashmere. They are a bit loose and long for me (size S, but I would have preferred XS). They’re so comfortable that I wear them as loungewear/pyjamas. I also noticed an issue with the overlock stitching, which I assume is why the product didn’t pass quality control. Nevertheless, I’m happy since I paid only €25 per piece, and these flaws are not visible.
References
- Icebreaker: LUXE RIB PULLOVER HOODY (Amazon Link) – €100, I got size XS
- Hanro: Woolen Silk Long-Sleeve Chemise. I got size S. The original price is €95, but I paid €25 on Vinted as these were factory seconds with minor defects.
Composition
- Icebreaker: 100% New Zealand merino wool. 19 microns. It comes from farms that have signed 10-year contracts with the brand and do not practice mulesing.
- Hanro: 70% merino wool, 30% silk. Hanro’s merino wool comes from South Africa. It is superfine merino wool with a fiber thickness of 16 to 18.5 microns, of excellent quality. It is mercerized and refined using superwash treatment, which gives it a special sheen and prevents pilling and itching. The wool comes from farms that do not practice mulesing, a controversial technique.
My Opinion
- Icebreaker : You can wear it for several days in a row without any smell. Sweat, if any, is efficiently wicked away. It is quite long and covers the hips. The sleeves have built-in thumbholes. The hoodie stands out and is only suitable for casual looks. Icebreaker also offers more discreet styles; you can read my extensive comparison here. Be cautious to only choose 100% merino items, as some of their t-shirts contain synthetic technical materials for athletes.
- Hanro : The stitching and design are more premium. The feel is exceptional thanks to the 30% silk blend. This brand specializes in this type of product and pays more attention to small details in the sewing. You can wear this piece under tight-fitting clothes with no issues. Second-skin effect. However, due to the 30% silk, you need to be more careful when washing. Hanro also offers products in Supima or Sea Island cotton, which are highly reputed and of excellent quality.
Whether it’s Icebreaker or Hanro, I highly recommend them!
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