Midwinter wool innerwear: joha and Tam Silk enthusiasts compare notes and share recommendations

Is that synthetic innerwear of yours really warm?

For years, many of us have worn synthetic innerwear simply because "the ads make it look warm" or "everyone else wears it." But once you stop to question that assumption, you may realize you've never actually confirmed whether it's truly warm.
Once that doubt sets in, it's natural to start wondering what exactly makes synthetic innerwear warm in the first place. And that naturally leads to comparing it with innerwear made from natural fibers like wool and silk. Many people are curious about these options but hesitate—put off by the itchy image wool has, or by the price difference compared to synthetic innerwear.
ZUTTO carries two wool innerwear brands: joha and Tam silk. In this feature, titled "Winter Wool Innerwear," we'll explore what makes natural-fiber innerwear appealing, along with some points worth knowing before you buy.

What wool can really do as innerwear

Among natural fibers, wool stands out for its excellent moisture absorption. Its curled fibers create countless tiny air pockets, which prevent heat from becoming trapped and help keep body temperature stable—making wool a comfortable choice that's warm in winter and cool in summer.

Merino wool also has natural resistance to bacteria, helping prevent the growth of the microbes that cause odor, so you can expect a deodorizing effect. This isn't just useful during the sweaty summer months—it's reassuring in the cold winter too.

The joha and Tam silk innerwear available at ZUTTO come in both 100% wool versions and wool-silk blends.

We asked longtime users: how do you like wool and silk innerwear?

We have a staff member who regularly wears both joha and Tam silk wool-silk innerwear. What's different from synthetic innerwear? What differences stand out between joha and Tam silk? Let's dig deeper from the perspective of someone who wears them daily.

Wool innerwear enthusiast: Staff member M

In charge of special-order products and promotional planning. Self-described as having a "normal level" of tolerance for wool's itchiness.

Here are the joha and Tam silk wool-silk innerwear pieces this staff member wears regularly.

The joha is in navy (right), and the Tam silk is in GREY (left).

First, why did you decide to wear both joha and Tam silk?

"I'd originally been wearing joha's short-sleeve wool innerwear and really felt how comfortable it was. For winter, I'd been wearing a long-sleeve synthetic innerwear, but it occurred to me that natural fibers like joha or Tam silk might actually be more comfortable, so I decided to get something new this winter. I was going to just pick one brand, but I got curious about whether the fit and feel would differ between them, so I ended up trying both."

What exactly makes wool-silk innerwear feel so comfortable?

"Even in winter, you break into a light sweat sometimes—like after a quick jog to catch the train, or from sitting near a heater. With synthetic innerwear, that sweat never seemed to dry, which left me feeling uncomfortable. In winter, my back and stomach don't get drenched, but I'd notice it under my arms and it would bother me. With wool-blend innerwear, though, it dries relatively quickly and the sweat doesn't turn cold on my skin—it's genuinely comfortable. That difference is really noticeable."

Do you feel a difference in warmth between synthetic innerwear and wool-silk innerwear?

"Comparing warmth is a tricky thing to do... I haven't tested this scientifically, so this is purely my personal impression, but with synthetic innerwear, I'd often notice that once I started sweating even slightly, my whole body would suddenly feel hot, and then just as quickly cool down again. With wool-silk innerwear, there's much less of that up-and-down—it just stays consistently warm."

So what differences do you notice between joha's and Tam silk's wool-silk innerwear?

"Both are blended at 85% merino wool and 15% silk, so I don't notice much difference in how they feel to the touch. But the sizing is quite different. joha fits snugly, close to the body, while Tam silk has more room around the arms and waist. There's also a slight difference in thickness—Tam silk feels a touch thicker and seems to stretch a bit more. So I switch between them depending on what I'm wearing on top: Tam silk under a loose sweater, and joha under a shirt or slim-fitting sweater."

△joha (top) layered over Tam silk (bottom). You can see that Tam silk is cut with more room to spare.

I have sensitive skin, and just hearing "wool innerwear" makes me itch a little—does it feel scratchy?

"Actually, the very first time I put it on after buying it, I felt a slight prickliness on the thin skin of the inside of my arm. I hadn't felt that with the short-sleeve type made of the same material, so I was surprised—wait, this is prickly! But after washing it a few times, that sensation disappeared. I guess you could say the wool fibers became accustomed to use, or something like that. Now I don't notice any prickliness at all, but I think this varies a lot from person to person, so I can't say for sure either way. Still, it's completely different from the prickly sweater feeling that people generally imagine when they hear 'wool'—it's quite soft and gentle."

One reason skin feels prickly is that it has become dry and sensitive. Whether the material is natural or synthetic, the way inner wear keeps you warm is by "generating heat in response to sweat." However, many of the materials commonly used in synthetic inner wear tend to absorb too much sweat. In other words, they also draw away the moisture your skin needs, which can lead to dry skin as a drawback. If you always wear synthetic inner wear, your skin may be drying out without you realizing it. If this sounds familiar, one option is to apply a moisturizing cream and try wearing inner wear made of natural fiber—not limited to wool silk, cotton works too—and see how your skin responds.

What's the difference between joha and Tam silk?

As mentioned by the staff member who loves using both, there isn't much difference in feel or warmth between joha and Tam silk. Let's take a closer look at their construction and sizing.

First, let's lay the joha and Tam silk inner wear on top of each other.

△joha (top) layered over Tam silk (bottom).

The length and sleeves are longer on the joha, while the Tam silk has more room in the body width.

Here's how they look when actually worn. The model is 158cm tall with a slender build, and typically wears size S-M or size 36 in clothing.

When worn, you can clearly see the difference in fit around the shoulders and arms. The joha fits snugly so it doesn't interfere with tops worn over it, while the Tam silk has enough room that it could even be worn as a cut-and-sew top on its own. The depth of the neckline is nearly the same for both, though the Tam silk's collar width (the width of the neck opening) may be slightly wider.