MicroModal and Lyocell (TENCEL fibers) run cooler and drier than cotton or synthetics because they wick moisture efficiently and breathe without holding heat. A relaxed fit compounds the advantage by allowing airflow rather than pressing fabric against skin.
By the time you notice you're sweating through your jeans on a ninety-degree commute, the underwear decision is already made, and if you picked by brand or how it felt in the store, you probably picked wrong. What actually keeps you cool comes down to two things: how fast the fabric pulls moisture away from skin, and how much airflow the fit lets through.
How the main fabrics actually compare
| Fabric | Moisture wicking | Breathability | Heat retention |
|---|---|---|---|
| Cotton | Low | Moderate | High when wet |
| Polyester / Nylon | Moderate | Low | High |
| MicroModal (TENCEL) | High | High | Low |
| Lyocell (TENCEL) | High | High | Low |
Cotton absorbs moisture well but holds it, which means a sweaty pair of cotton briefs becomes a warm, damp compress. Synthetics like polyester wick faster but don't breathe, so heat builds under the fabric. TENCEL fibers, MicroModal and Lyocell, are derived from wood pulp and handle both problems: they pull moisture away from skin and release it quickly, so the fabric stays drier and cooler against your body. [1]
Fit is the other half of the equation. Compression-style underwear holds fabric tightly against skin regardless of material, which limits airflow and traps heat in the one area that benefits most from staying cool. A relaxed cut creates a small but real air gap. Research on garment fit and thermoregulation confirms that fit independently affects local temperature, separate from fabric choice. [2]
- Hot weather daily wear: MicroModal or Lyocell in a relaxed brief or boxer brief.
- Training: Same fibers, but watch for compression cuts marketed as performance, which often prioritize support over airflow.
- Sauna or steam: You want fabric that won't hold heat after you leave. Natural and naturally derived fibers recover faster than synthetics.
Oakman launches Fall 2026. Founding members get first access and founding pricing locked in. Reserve your spot.
Where Oakman fits
Oakman is built specifically for active men looking for scrotal cooling all day and want the option of a cold pack for cooling in the sauna or after heat exposure. The fabric is TENCEL MicroModal, naturally derived from wood pulp rather than plastic, blended with ROICA V550, a clean Japanese stretch fiber, rather than conventional spandex. The fit is athletic with a gusset, an extra panel that gives the testicles room and airflow. Dyes are bluesign approved, so what touches your skin is controlled all the way through the supply chain. The Founding 100 get first access when the brand launches Fall 2026.
Related reading
Related reading
Frequently asked questions
Does underwear fabric actually affect how hot you feel down there?
Yes, meaningfully. Fabrics that hold moisture trap heat against skin, while breathable fibers that wick and release moisture keep the area cooler. The difference between a wet cotton brief and a dry MicroModal one is noticeable within an hour of activity.
Is cotton or synthetic better for staying cool?
Neither is ideal. Cotton absorbs sweat but holds it, turning damp and warm. Synthetics wick faster but don't breathe well, so heat accumulates under the fabric. Naturally derived fibers like MicroModal and Lyocell handle both moisture and airflow better than either. [1]
Does underwear fit affect temperature as much as fabric?
Fit matters independently of fabric. A compressive cut holds fabric against skin and limits airflow regardless of what the fabric is made from. A relaxed fit creates enough space for air to circulate, which compounds the benefit of a breathable material. [2]
Does underwear tightness affect male fertility?
Research suggests it can be a factor. A large study of men attending a fertility clinic found those who primarily wore boxers had meaningfully higher sperm concentration than those in tighter styles. [3] More detail at our post on tight underwear and fertility.
What should I look for in underwear for sauna use?
Prioritize fabric that releases heat and moisture quickly after you leave the sauna, not just during. Naturally derived fibers recover faster than synthetics. A relaxed fit also helps the area that needs to stay cool return to its normal temperature more efficiently.
This article is for general educational purposes and is not medical advice. If you have specific concerns about fertility or your health, talk to a qualified clinician.
References
- Comparative Assessment of Sensory Comfort Properties Across Eco-Friendly Textile Materials for Apparel. 2025. Journal of Natural Fibers (Taylor & Francis). [Link]
- Zleczewski, et al.. (2024). Garment fit, scrotal thermoregulation, and male fertility outcomes: a narrative review. Translational Andrology and Urology. [Link]
- Minguez-Alarcon L, et al.. (2018). Type of underwear worn and markers of testicular function among men attending a fertility center. Human Reproduction. [Link]
