Are Merino Wool Socks Hot?
Wool is a very diverse and dynamic material, that works in all types of weather. From the hottest day of the year to the coldest, and depending on where you live, even both on the same day. This is why wool, specifically Merino, is called a “super-fabric” and is the fabric of choice for premium outdoor clothing and active-wear.
Most synthetic fibers are designed to emulate Merino wool, but like most copycats, you can’t emulate the real thing.
Merino socks don’t trap moisture, which keeps your feet cool, light, airy, and comfortable, making Merino ideal for summertime activities.
Merino is also anti-microbial, meaning your feet won’t stink when they sweat, and unlike the traditional wool, ultrafine Merino doesn’t itch because of its soft and ultra-fine fibers.
Merino wool: keeps you cool & warm
In desert conditions, wool is the best fabric choice because of its ability to maintain constant body temperature, even though deserts have large diurnal (daily) temperature fluctuations, with extreme heat during the day and frigid temps at night.
This is why nomadic Bedouins of the Sahara and Arabian Deserts, wear robes made from wool.
merino wool is Breathable
Wool can absorb up to 35% of its own weight in water without feeling damp. While the benefits of this are obvious when it’s cold, they are a little more technical when it’s hot.
When you sweat, your clothes absorb water vapors. Wool will absorb these sweat vapors and move moisture away from your skin, then evaporate the moisture, into the air, without creating fluctuations in your skin temperature.
When people talk about clothing being “breathable,” what they are really talking about is the ability of the clothing to evaporate sweat off the skin the same way that you would while being naked…..which is also the same way the wool functions on the Merino sheep.
Merino wool is naturally crimped
Many fibers hold moisture against your skin. When it's hot, this makes the clothes feel sticky and it also prevents your sweat from evaporating, which will make you even hotter. The natural crimp in wool fibers forces each strand to press against each other, as opposed to side-by-side or lying flat-together.
This keeps tiny air pockets, which act as microscopic insulators, and is one of the main reasons why Merino wool keeps you both warm when it’s cold and cool when it’s hot.
Cool when it's hot and warm when it's cold --- Merino Wool EXPLAINED
Merino wool is a dynamic insulator, and like all great thermos, it keeps you warm in the cold and cool in the heat.Through convection, air can transport heat from one place to another, and it’s through convection that your home loses heat/AC (through doors, windows). Merino wool has tiny air pockets that form from the natural crimp in each fiber strand. These microscopic air pockets limit the amount of circulation and temperature losses, thus retaining heat or cold…depending on the weather.
An easier way to think about this is by picturing a Styrofoam cooler. The Styrofoam has tiny pockets of air that act as insulators for heat or cold, depending on what’s inside the cooler…hot coffee or cold brew, perhaps.
Schematic diagram of a Merino wool fibre showing the major structural features of non-medullated wool. - - (Image Source: Theopoline Itenge, 2007)
Merino Wool: Moisture-wicking, Humidity & keeping you cool
Merino wool absorbs water from both your skin and the atmosphere, which creates a dry microclimate against your body while keeping your skin at its ideal temperature (90°F/33°C).
Dopey sheep or complex superfiber? I think we all know the answer
In addition to wool being able to absorb nearly 1/3 of its weight, Merino also repels water. Wool fibers are made up of a filmy outer layer that helps to repel moisture by drawing in vapors from the atmosphere (during high-humidity conditions).
The tiny pores in the epicuticle layer break the hydrogen bond of water, which then allows moisture to evaporate out before it even had a chance to come in contact with your skin. It’s no wonder that synthetic materials are designed to duplicate the natural fibers of Merino sheep.
merino wool socks keep your feet cool, comfy, & blister-free
Of all the pieces of clothing, socks are among the most important, especially when working or exercising in hot conditions. The palms of your hands and the soles of your feet have more sweat glands than any other part of your body.
Wearing Merino socks, especially during balmy weather, is a great choice. Merino will absorb moisture from your sweaty feet, which then gets evaporated into your shoe.
Socks, like cotton, trap heat, and the sweat that is absorbed doesn’t evaporate out, leaving you stewing in a pool of your own sweat. If you happen to be walking in these soggy, perspiration filled, bacteria infested socks, then blisters develop.
socks & frictional blisters
Frictional foot blisters are the most common skin injury in sports. Many people blame their boots or shoes for causing blisters, yet the sock is more to blame than the shoe. Blisters are caused by friction between the skin of the foot and the sock, with more friction increasing as the sock gets wetter.
Different fabrics cope with moisture differently. However, one of the main ways to reduce blisters is to wear socks that absorb lots of moisture, as this will reduce friction between the sock and skin.
A 2012 study that was published in The Annals of Occupational Hygiene looked at sock fabric and blister prevention and noted that the best sock was a Merino wool blend (50% Merino wool), which was best at regulating temperature, dampness, friction, and comfort.
merino, “smart” wool & synthetic
Superfine Merino wool has superior water absorbency, is quick-drying, and transfers moisture/sweat away from your body.
Synthetic fibers have the same qualities as Merino, which makes sense since synthetics are refurbished laboratory mimicries of Merino. This is why SmartWool, the apparel company, uses Merino wool and has branded it as “Smart.”
Related article: “Are Merino Socks Itchy?” and why do some fabrics itch while others don’t??
Jesse is Director of Pedal Chile and lives in Valdivia, Chile. Jesse has a Master of Science in Health & Human Performance and a Bachelor of Science in Kinesiology. Hobbies: Mountain biking, snowboarding, reading, taster of craft beers, user of compression socks, researcher, & Merino sock wearer.
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Sources & references
Bogerd, C., Niedermann, R., Brühwiler, P. and Rossi, R. (2012). The Effect of Two Sock Fabrics on Perception and Physiological Parameters Associated with Blister Incidence: A Field Study. The Annals of Occupational Hygiene, 56(4).
Brennan, F.H., Jackson, C.R., Olsen, C. and Wilson, C. (2012). Blisters on the Battlefield: The Prevalence of and Factors Associated With Foot Friction Blisters During Operation Iraqi Freedom I. Military Medicine, 177(2), pp.157–162.
BRYANT, C. (2009). How does wool keep you warm even when it’s wet? [online] HowStuffWorks.
Itenge, Theopoline. (2007). Identification of genetic markers associated with wool quality traits in merino sheep.
Hu, J., Irfan Iqbal, M. and Sun, F. (2020). Wool Can Be Cool: Water‐Actuating Woolen Knitwear for Both Hot and Cold. Advanced Functional Materials, p.2005033.
Mares, M.A. (2017). Encyclopedia of deserts. Norman: University Of Oklahoma Press.
Nawaz, N., Troynikov, O. and Watson, C. (2011). Thermal Comfort Properties of Knitted Fabrics Suitable for Skin Layer of Protective Clothing Worn in Extreme Hot Conditions. Advanced Materials Research, 331, pp.184–189.