Can Merino Wool Really Heat Up in Moist Air? The Answer Will Surprise You!
Why Merino Wool Feels Warmer When It’s Damp & Cold: How It Turns Humidity into Instant Warmth
Venturing out of a warm home into a cold, damp, wintry morning, you might actually feel a rise in temperature—if you’re wearing Merino wool!
As early as 1858, French scientist Coulier discovered that wrapping wool fabric around a thermometer and moving it from a dry atmosphere to one saturated with moisture caused the thermometer’s temperature to rise.
Research by the CSIRO takes this a step further. Tests showed that people wearing Merino wool garments could detect a temperature increase when moving from dry to cool, moist conditions. In contrast, synthetic fibers under the same conditions produced a drop in temperature.
The key to unraveling this phenomenon lies in the structure of the wool fiber. When dry Merino wool is exposed to moist air, water molecules are attracted to sites within the fiber’s internal structure, where molecular forces hold them. This process releases heat energy (known as the heat of sorption). Remarkably, Merino wool can absorb up to 35% of its dry weight in moisture—without feeling wet. (Click here for a more in-depth explanation of the heat of sorption.)
As Merino wool absorbs water vapor, it also releases heat—equivalent to roughly eight hours of warmth from an electric blanket!
This heat is released within about two minutes, gradually decreasing until the wool’s moisture content balances with the surrounding humidity.
The heat of sorption from Merino wool garments benefits anyone braving damp, cold weather. People have long associated Merino wool with warmth; thanks to CSIRO’s research, now we know why.
Merino wool thermals adapt to your body, keeping you warm when damp and cool when active—all thanks to science perfected over millennia.
