How Does Cooling Clothing Work?

You are probably familiar with moisture-wicking clothing that promises to keep you both dry and cool. Maybe you have even wondered how a shirt or a pair of pants with evaporative cooling technology can help keep you from overheating on a hot day or during physical activity.

After all, maintaining an optimal body temperature is essential when you are in hot conditions or participating in activities that can raise your body’s core temperature. But is cooling clothing the answer?

Experts claim these garments—which are sought after by athletes and outdoor enthusiasts alike—not only prevent overheating but also may be able to improve comfort and performance. To help you make sense of these claims on what cooling garments can (and cannot) do, we explore the details of how they work below.

Evaporative Cooling Technology

Evaporative cooling clothing, commonly seen in vests or towels, uses the fundamental scientific property of 'phase change' to keep your temperature from rising. Evaporation takes place when liquid (like sweat) turns into a vapor or evaporates. Because heat energy is used to change the water to vapor, a cooling sensation occurs.

Clothing using evaporative technology relies on this 'phase change' process. First, you wet the vest or towel, wring it out, and then wear it over your other clothing. The fabric remains slightly damp, allowing the water particles to slowly evaporate as air passes over them. During the evaporation process, you'll experience cooling as heat dissipates from your body.

"The fabric releases moisture through evaporation on the top face of the fabric, which results in the skin being kept dry," says Lara Smith, founder of cooling sleepwear and sheets companies Lusomé and SOMÉ.

Moisture-Wicking Fabrics

Fabrics that wick moisture from the body work in a similar fashion. However, instead of getting them wet first, like with cooling towels, they use your sweat to go through the cooling evaporative process. When you get warm and begin to perspire, these special highly-absorbent fabrics draw moisture away from your body as quickly as possible.

As the heat is drawn away from your body, they pull moisture from your skin into the fabric, where it can be turned into a vapor. Most moisture-wicking fabrics strive to pull as much moisture and humidity away from the skin as possible and then disperse it across the largest surface area of the fabric to maximize evaporation.

Smith says two types of fabric are used. These include hydrophilic and hydrophobic fibers. Hydrophilic fabrics absorb and draw moisture in, she says. Meanwhile, hydrophobic fabrics repel moisture, so the fabric and skin won't stay wet.

Breathability and Ventilation 

Some clothing may incorporate breathability and ventilation, while others rely solely on these features, such as a vented rain jacket. Breathable fabrics, also known as fabrics with air permeability, help to prevent heat, sweat, and humidity from being trapped against your body.

These fabrics are better at allowing airflow, unlike polyester, which holds it against your skin. Added ventilation, usually seen as strategic cuts or holes in the clothing, can increase airflow.

Smith notes that although these features can influence the thermal comfort factor of a garment, it is still important to have a mechanism to eliminate sweat and bacteria, like a wicking fabric. 

Phase Change Materials (PCM)

Phase change materials (PCM) were largely developed by NASA when they were working on temperature control for space suits. PCMs rely on materials that change states at various temperatures, similar to the wax of a candle as it liquefies and solidifies.

Sometimes, when used in textiles, these materials are called 'thermocules.' The molecules within the fabric change state depending on temperature fluctuations, so they either absorb or release heat, helping to adjust your body temperature quickly. Think of it as built-in temperature control, also known as thermoregulation.

Thermoregulation is the name for maintaining a steady internal body temperature. It's a biological mechanism that all mammals possess, which is why we sweat when we are hot or shiver when we are cold.

During phase changes, PCMs absorb excess heat from your body and then release it as they phase change again when the ambient temperature drops. In other words, they cool you when you get hot and offer warmth when you get cold.

In turn, this can aid performance and comfort. Since early NASA development, PCMs have found their way into various products, like bedding, medical supplies, and athletic clothing, as a method of thermoregulation. 

Fabric Innovations for Cooling Clothing

There have been other cooling clothing innovations too, such as cool-touch fabrics. These textiles often have a special finish, though some possess it in their natural state, that allows them to feel cool to the touch. The scientific term is 'thermal effusivity,' and it's the reason why some fabrics feel cool when they touch your skin.

The heat from your body is transferred to the textile and a high thermal effusivity makes it feel very cool to the touch. Products like jade powder or polyethylene (PE), which have high thermal effusivity, can be added to fabrics to help them feel cooler and promote heat transfer away from your body.

To embed these cooling agents, a method called micro-encapsulation is often used. This technique captures small quantities of agents into tiny packages, known as microspheres, which can then be embedded into the fabric. Microspheres are also helpful because most only release or activate their agents under certain conditions.

"It is a mechanism to envelop substances [by coating them with] extremely small capsules," says Smith. "Think aloe-infused socks."

Finally, reflective coatings may also help to cool the wearer. Using reflective surfaces to deflect the sunlight and reduce heat absorption, maximizing coolness, isn't new. However, reflective coatings have advanced since their inception, and many can now be added to fabrics without drastically changing their other properties.

Another benefit Smith notes is increased visibility, which is ideal for people like runners, cyclists, or outdoor construction workers who need to have the safety element. 

Applications and Benefits of Cooling Clothing

Cooling fabric has expanded into a variety of clothing options and gear, such as high-performance compression leggings. It's excellent for athletes who want to enhance their performance during strenuous workouts. Cooling textiles with the added benefit of antimicrobial agents or reflective coatings can also keep athletes safe while drawing heat away from the body. This ultimately aids their comfort by reducing heat stress and preventing overheating during exercise.

Outdoor enthusiasts can particularly benefit from cooling clothing, especially in hot and sunny conditions. Hikers, campers, and home gardeners can use cooling textiles to help regulate their body temperature outdoors and prevent heat-related illnesses like heat stroke. Similarly, those living in hot climates may turn to cooling clothing to promote evaporation and reduce heat build-up for comfort and relief during relentless humidity and warmth.

Limitations and Considerations

Although moisture-wicking and cool sensation clothing can provide relief and comfort, it does have its limitations. In high-humidity environments, its effectiveness may be decreased as evaporation is typically slower. Additionally, evaporative clothing is only helpful as long as it stays damp. When the fabric dries out, it will need to be remoistened. 

When choosing cooling clothing, getting the proper fit and design for your activity is imperative. Most moisture-wicking fabrics must be in direct contact with your skin to remove moisture and disperse it into the fabric. If you wear these textiles as an outer layer or a very loose base layer, they may not work as effectively.

Many clothing items also will be geared toward a certain activity, and following these recommendations is wise. For example, a hiker might want a thermal regulating shirt with a reflective coating for UV protection. A cyclist will use a moisture wicking base layer under their jersey in the summer months to not only aid in the cooling process but also to collect much of the sweat produced on a long, hot bike ride and perhaps save the expensive jersey from ultimately getting sweat stains. At the same time, a runner may choose a lighter, moisture-wicking fabric with enhanced breathability. After you've selected the right cooling fabric for your intended purpose, proper care and maintenance are required to keep the garment functioning at optimal levels.

"In general, gently wash and dry and do not use any type of softener or bleach," says Smith. However, she cautions that fabrics vary, making it important to follow the specific item's care instructions. Following the instructions will extend the life of your clothing and help it maintain optimal cooling performance. 

Bottom Line

Cooling clothing can use various techniques to draw heat and moisture away from your skin for a cooling sensation. It can be beneficial for all types of users, including athletes, those who enjoy the outdoors, or hot climate dwellers.

However, choosing the appropriate type and fit is key for optimal comfort, performance, and prevention of overheating. Before committing to a brand or type, explore your options while considering your individual needs, activity levels, and environmental conditions.