Cotton or cooling fabric: which should you choose when it’s really hot?

Why does your cotton T-shirt let you down at 30°C? The answer lies in 4 technical fibers.

Whether you’re an athlete completing a 15-kilometer run in 33°C heat, a parent accompanying your children to a school sports day under the July sun, or a person with limited mobility who needs to stay cool for several hours without the option to change clothes: everyone has experienced that moment when the fabric stops working for you and starts working against you. Cotton sticks, feels heavy, and traps moisture. The activity becomes a struggle.

At G-Heat, we’ve been designing thermoregulatory clothing and gear since 2017. Our role is not medical—it is technical. We help the body maintain its thermal equilibrium, regardless of external conditions, by providing the right materials at the right time. Before designing our products, we must understand how each fiber actually behaves in response to heat and sweat.

Cotton vs. cooling fabrics: what really happens on your skin

Moisture Management: Absorption vs. Wicking

Cotton absorbs sweat like a sponge: up to 27 times its weight in water. This feels comfortable at first, but becomes a problem after just a few minutes of activity. Saturated fibers remain damp against your skin for hours and lose all ability to evaporate moisture. Technical fabrics work the opposite way: they wick moisture to the fabric’s surface to allow it to evaporate continuously, without ever reaching saturation.

This difference makes all the difference over time. In hot weather, waterlogged cotton becomes heavy, cold on the surface but clinging to the skin, and forces you to give up well before the end of the activity. For an athlete or a family on a long day outdoors, the difference in performance is immediate and measurable.

The feeling of coolness: immediate effect vs. lasting effect

A cotton T-shirt feels pleasantly cool when you put it on, thanks to its softness and absorbent structure. This sensation reverses as soon as you start sweating. Technical fabrics maintain consistent coolness, enhanced by technology such as jade microcrystals (JadeCool™), active evaporation weave (TechCool™), moisture-retaining fibers (PolyCool™), or phase-change materials (PhaseCool™), each of which activates a distinct cooling mechanism upon contact with body heat.

A JadeCool men’s cooling UV-protective T-shirt, for example, provides a perceived cooling effect of 15°C within the first 15 seconds of contact, without any prior activation: no need to soak it in water, no batteries required. The result comes from the mineral integrated into the fiber, not from a surface treatment.

Drying speed: a key factor during heat waves

Cotton takes 2 to 3 times longer to dry than technical polyester. At 35°C with sustained exertion, this difference means wearing a damp garment for hours, persistent chafing against the skin, and a gradual loss of thermal efficiency. The rapid drying of TechCool™ fabric, based on a dry technical weave (no wetting required), allows you to stay functional without ever reaching saturation: sweat evaporates during exertion, not afterward.

See also: Guide to UPF 50+ certified clothing

The 4 G-Heat technologies compared to cotton: a fiber-by-fiber analysis

JadeCool™: active mineral conduction

JadeCool technology incorporates jade microcrystals directly into the polyester fiber. Jade is a natural thermal conductor: upon contact with the skin, it captures body heat and transfers it to the garment’s surface, where it dissipates into the air. No activation, no wetting required. The effect is passive and immediate, lasting wash after wash because the crystals are embedded within the fiber itself, not just as a surface finish.

JadeCool™ combines this active cooling with UPF 50+ protection: over 97.5% of UV rays are blocked by the dense weave. It is the most versatile G-Heat technology, found in Anti-UV t-shirts, towels, and neck gaiters. The UV protection comes from the reinforced weave, not the crystals themselves.

TechCool™: passive temperature regulation through dry weaving

TechCool™ technology does not rely on a mineral or chemical treatment, but on the very structure of the weave. An ultra-lightweight, open-weave technical mesh promotes air circulation and the natural evaporation of sweat. No activation or wetting required: the fabric works dry, from the very first movement. This is the preferred technology for high-intensity sports, where heavy sweating requires constant moisture wicking without saturation.

A pair of TechCool™ men's cooling athletic shorts perfectly illustrates this principle: lightweight, thin, stretchy, and breathable, they move with you without resistance or moisture retention.

PolyCool™: controlled moisture retention for prolonged exposure

Unlike JadeCool™ and TechCool™, PolyCool technology works through moisture retention: its super-absorbent fibers capture water (activated by moisture or intense perspiration), then gradually release it through controlled evaporation over several hours. This technology is particularly suited for prolonged static exposure to the sun, whereas TechCool™ and JadeCool™ see their effectiveness enhanced by movement.

A PolyCool cooling sports cap activates upon contact with moisture to provide prolonged cooling on the head and neck for several hours: ideal for a family spending the day outdoors or a cyclist on a long ride.

PhaseCool™: phase-change materials for confined environments

PhaseCool technology relies on phase-change materials (PCMs) microencapsulated within the fiber. These materials absorb body heat by changing from a solid to a liquid state, then gradually release it as they return to room temperature. The cooling effect is precise and controlled, independent of ambient humidity. This is G-Heat technology, designed for confined spaces or areas with poor air circulation, where evaporation is limited.

The EVO PhaseCool cooling sleeves work at room temperature without any specific activation. Worn on the forearms, they maintain stable thermal regulation for 2 to 3 hours, even without heavy sweating: a key piece of equipment for people with limited mobility who cannot rely on physical exertion to trigger sweating.

Learn more: JadeCool Technology: How Does It Work?

Comparison Chart: Cotton vs. 4 G-Heat Technologies

Criterion	Classic Cotton	TechCool™	JadeCool™	PolyCool™
Active principle	Passive absorption	Technical weave with natural evaporation	Jade microcrystals (conduction)	Hydro-retentive fibers (controlled evaporation)
Required activation	None	None (dry)	None (passive, skin contact is enough)	Moistening (soaking or sweating)
UV protection	Very low (UPF 5–10 for white cotton)	UPF 50+	UPF 50+ (dense fabric)	UPF 50+
Contact Qmax index (W/cm²)	0.08 to 0.12 (below the cool feeling threshold of 0.15)	High Qmax (≥ cool feeling threshold)	High Qmax (≥ cool feeling threshold)	High Qmax (≥ cool feeling threshold)
Estimated drying time	2–3 hours	20–30 minutes	30–45 minutes	Variable (progressive evaporation)
Cooling effect duration	Immediate, then disappears once saturated	Continuous during effort (active evaporation)	Permanent (crystals integrated into the fiber)	Several hours after activation
Optimal use	Mild daily use, rest, indoors	Intense sport, running, CrossFit	Versatile: sport, family, UV accessories	Long static exposure, cycling, hiking
Representative G-Heat products	—	Sports shorts, sports headband	Anti-UV T-shirt, neck gaiter, XL towel	Sports cap, cooling vests

“When choosing a fabric for summer, you’re not just choosing a color or a cut. You’re choosing a heat-transfer mechanism. Cotton transfers heat well at rest; but as soon as you start moving, it becomes saturated and traps heat. It’s this saturation that our technologies aim to eliminate. »

— Gwenaël Fournet, Product Expert at G-Heat

Cotton: its real strengths and its actual limitations

The True Benefits of Cotton

Comfortable, soft, breathable in moderate conditions, and hypoallergenic: cotton remains an excellent choice for everyday wear in mild weather, indoors, or during low-intensity activities. It remains the go-to fabric for those with very sensitive skin who cannot tolerate certain synthetics. Its natural softness and pleasant feel explain why it has dominated the textile industry for decades.

Combed organic cotton, fine percale, or lightweight jersey offer better thermal performance than standard thick cotton. The weight (g/m²) and weave matter just as much as the fiber itself: a 200-thread-count percale sheet breathes very differently from a 250 g/m² jersey.

Limitations in hot and humid climates

As soon as you start sweating, cotton becomes a heat trap. Heavy fabric, trapped moisture, friction against the skin, and unpleasant odors amplified by maceration: three hours in the sun are enough to turn a comfortable T-shirt into a burden. The National Institute for Research and Safety (INRS) identifies the type of clothing as one of the primary factors in preventing risks associated with extreme heat, whether at work or during sports activities.

For a sports outing, a family day outdoors, or prolonged exposure with limited mobility, 100% cotton is no longer the best choice above 28–30°C.

UV protection: an often-overlooked factor

A classic white cotton T-shirt offers a UPF rating of 5 to 10, which is very low sun protection. According to Santé publique France, UV exposure is one of the main risk factors for skin cancer, exacerbated by extended time spent outdoors. The cooling t-shirts JadeCool™ and TechCool™ G-Heat feature UPF 50+ protection: over 97.5% of UV rays are blocked by the dense weave, compared to 5–10% for standard cotton. This difference directly benefits athletes, families spending extended time outdoors, and people whose limited mobility restricts their ability to move into the shade.

Don't miss: Heat rashes in adults: how to relieve and prevent them?

Which fabric for which use: the practical guide by persona

Intense exercise and extreme heat: when every minute counts

For running, CrossFit, or summer cycling in temperatures above 28°C, it’s not just about comfort—it’s about maintaining performance. Moisture-saturated fabric slows you down, increases friction, and makes you want to quit before the end of your workout. 100% cotton is not recommended for endurance sports once temperatures exceed this threshold.

The G-Heat solution for athletes: pair a JadeCool men’s cooling anti-UV T-shirt for cooling comfort and UV protection with TechCool men’s cooling athletic shorts for quick-drying performance and freedom of movement. A top-and-bottom combo designed for uninterrupted, sustained effort.

Outdoor family activities: long-lasting protection

Whether it’s a school sports day, an afternoon at the park, or a weekend camping under the sun, families need gear that lasts for hours without needing frequent reactivation. Prolonged exposure without intense movement calls for technologies with a lasting passive effect. When residual moisture limits evaporation, conduction takes over: a JadeCool cooling neckband works through direct contact with the neck area, without relying on dry air. Blood cooled at the source circulates throughout the body.

For the head, a PolyCool cooling sports cap protects and cools for several hours after activation. Complete your set with a JadeCool XL cooling towel (UPF 50+): unfolded in the shade or placed on the back of the neck, it maintains a surface temperature of 15°C as long as it remains slightly damp. Explore the full range of cooling towels and cooling neck wraps to find the right solution for your family.

Reduced mobility: staying cool without relying on physical exertion

For someone in a wheelchair, recovering from illness, or with limited mobility, natural thermoregulation through sweating is reduced: the body produces less sweat to work with. Technologies that rely exclusively on evaporation (TechCool™) or humidification (PolyCool™) are therefore less effective. PhaseCool™ takes over by directly absorbing body heat without relying on perspiration.

EVO PhaseCool cooling sleeves are worn on the forearms, an area with high vascular density: the cooled blood from this area circulates throughout the body. A discreet, self-contained cooling accessory that operates for 2 to 3 hours per cycle without requiring specific activation. The range of cooling sleeves also includes standard versions for shorter periods of exposure.

How to read a label and make the right choice

Key factors to check regarding composition

Given the proliferation of “cooling” claims, always check:

• Fiber percentage: a blend with 90% technical polyester is nothing like a blend with 50% cotton.
• Weave type: percale, jersey, piqué, openwork; the weave determines breathability just as much as the fiber.
• Weight in g/m²: a key indicator of weight and breathability. Below 160 g/m², you enter the optimal lightness range for warmth.
• Verifiable technical claims: quick-dry, moisture-wicking, UPF certified, measured thermal conductivity.
• Certifications: OEKO-TEX, GOTS, quantified lab tests with standardized protocols and identified testing bodies.

Weight and knit structure

A lightweight fabric (less than 160 g/m²) with an open knit promotes air circulation and evaporation. A heavy or tight fabric, even with the same technology, can trap heat. Adjust the weight to your activity level and the climate: the hotter and more humid it is, the lighter and more open the fabric should be. All G-Heat cooling garments are designed with this criterion of lightness as the starting point for the range.

The Qmax index: the objective measure of cooling upon contact

Qmax is the benchmark indicator for objectively measuring a fabric’s cooling power upon contact with the skin. Expressed in watts per square centimeter (W/cm²), it quantifies the maximum intensity of the heat flux dissipated by the fabric upon contact, according to the Japanese standard JIS L 1927 or the Chinese standard GB/T 35263. The higher the value, the more pronounced the sensation of coolness is the moment the skin touches the fabric.

Reference thresholds recognized by international textile standards:

• Less than 0.10 W/cm²: negligible cooling effect. This is the range for conventional cotton and standard polyesters.
• 0.10 to 0.15 W/cm²: neutral to slightly cool sensation.
• 0.15 W/cm²: official threshold above which a fabric can claim a “cool feeling” effect according to the GB/T 35263-2017 standard.
• 0.15 to 0.20 W/cm²: distinct coolness, perceptible upon contact.
• Greater than 0.20 W/cm²: intense coolness, typical of advanced cooling textiles with mineral fillers or super-absorbent polymers.

In practice: a classic white cotton T-shirt ranges from 0.08 to 0.12 W/cm², below the official coolness threshold. G-Heat technical textiles feature a high Qmax rating, ensuring a cooling sensation from the very first second of contact. JadeCool™ technology harnesses the natural thermal conductivity of jade microcrystals to achieve these levels; PolyCool™ technology relies on super-absorbent fibers that prolong the effect through controlled evaporation.

On a label or technical data sheet, always check for a measured Qmax value, along with the test protocol (JIS L 1927 or GB/T 35263) and the temperature difference used (ΔT 10 °C or 15 °C). In the absence of this information, the “cooling” claim remains unverifiable.

Care: preserving cooling properties over time

To maintain the performance of your technical garments over time, follow these guidelines:

1. Wash at 30°C maximum, never hotter.
2. Avoid fabric softeners, which clog the micro-channels and degrade the surface treatments.
3. Air-dry; do not use a dryer.
4. Do not iron areas treated with cooling finishes.
5. Store flat, away from direct light.

“In the field, the best gear is the one you forget you’re wearing. When you stop thinking about the heat during your workout, that means the fabric is doing exactly what it’s supposed to. You’re 100% focused on your goal.”

— Romane Benderradji, Communications Manager at G-Heat

Why choose G-Heat for your cooling gear

Faced with the complexity of materials and the proliferation of marketing promises, G-Heat offers a straightforward approach: solutions that are tested, measured, and designed for real-world conditions.

• Expertise in textile thermoregulation since 2017: G-Heat designs gear to keep the body within its comfort zone, in both heat and cold.
• 4 complementary and well-documented technologies: JadeCool™ (mineral conduction), TechCool™ (dry technical weaving), PolyCool™ (long-lasting moisture retention), and PhaseCool™ (phase-change materials) cover all thermal exposure scenarios.
• Solutions designed for every use: sports, outdoor family activities, limited mobility, professional environments. Each product addresses a real, documented need, not a generic promise.
• Sustained performance: Jade crystals and G-Heat technical fibers are integrated into the fabric’s structure, not just applied as a surface finish. Their properties withstand repeated wash cycles.
• Technical transparency: Certified UPF, measured perceived coolness, documented duration of effect. No unverifiable promises.

Conclusion

Cotton and cooling fabrics are not competitors: they address different physical needs. For a mild, calm day, cotton remains a comfortable choice. For intense heat, sustained exertion, a family day in direct sunlight, or prolonged exposure with limited mobility, G-Heat gear takes over with measurable performance: active cooling upon contact, continuous optimized moisture wicking, and UPF 50+ certified UV protection. Explore the full range of cooling apparel and find the gear suited to your activity.

Whatever the weather. G-Heat, in all weather conditions.

FAQ

Is cotton really less effective than cooling fabrics in extreme heat?

Yes, as soon as you start sweating. Cotton absorbs moisture but traps it against the skin, creating a sticky feeling and added weight. G-Heat technical fabrics continuously wick it away to keep the skin dry and maintain lasting coolness. Above 30°C with moderate exertion, the difference in performance is immediate and measurable.

What is the difference between a breathable fabric and a cooling fabric?

A breathable fabric allows air to circulate without necessarily wicking away sweat. A cooling fabric goes further: it actively wicks away moisture and incorporates an active mechanism to reduce perceived heat, through mineral conduction (JadeCool™), optimized natural evaporation (TechCool™), controlled water retention (PolyCool™), or phase change (PhaseCool™).

Do G-Heat products work without prior activation?

It depends on the technology. JadeCool™ and TechCool™ are entirely passive: no wetting, no batteries; the effect begins upon first contact with the skin. PolyCool™ requires activation by wetting to trigger its maximum controlled evaporation effect. PhaseCool™ (EVO sleeves) works at room temperature without specific activation.

How should you care for a cooling garment to maintain its properties?

Wash at 30°C maximum, without fabric softener, and air-dry. Avoid the dryer and high temperatures, which degrade technical fibers. For JadeCool™ products, the jade crystals are integrated into the fiber and withstand repeated wash cycles: performance does not depend on a surface finish that may wear off.

Which fabric should a person with limited mobility choose in hot weather?

PhaseCool™ is the most suitable technology: it works by directly absorbing body heat without relying on sweat or movement. EVO PhaseCool™ cooling sleeves worn on the forearms help maintain stable thermal regulation for 2 to 3 hours, even during low physical activity in confined spaces.

Is the UPF protection of G-Heat cooling fabrics effective?

Yes, for certified products. Standard white cotton offers a UPF of 5 to 10 (very low protection). JadeCool™ and TechCool™ G-Heat fabrics achieve UPF 50+: over 97.5% of UV rays are blocked by the dense weave. This protection is integrated into the fabric’s structure, not a chemical surface treatment, and remains stable over time and after washing.

Which G-Heat technology is best suited for extended outdoor family use?

JadeCool™ and PolyCool™ are complementary for this use. The JadeCool™ cooling neckband works through direct contact without activation. The PolyCool™ cooling sports cap protects the head for several hours after being moistened. The JadeCool™ XL cooling towel (UPF 50+) completes the protection for breaks or periods of static exposure.

Sources and references

[1] “Work and Heat: Key Takeaways”, National Institute for Research and Safety (INRS)

[2] “Vigilanses No. 16 — Safety of Substances in Textiles”, ANSES Vigilanses

[3] “Work and Heat: Preventive Measures”, National Institute for Research and Safety (INRS)

[4] “Weekly Epidemiological Bulletin 2025-7”, Santé publique France

[5] “Heat Waves and Extreme Heat: Best Practices”, Ameli.fr

[6] “Functional and Smart Textiles”, French Institute of Textiles and Clothing (IFTH)

[7] “JIS L 1927: Testing methods for contact cool feeling of textiles”, Japanese Industrial Standards Committee (JISC) — reference standard for measuring the Qmax index (maximum value of heat flux upon contact, W/cm²)