KORETEX TEXTILE GROUP

What is Moisture Transfer Rate (and Why Does It Matter)?

By gaining a deeper understanding of moisture transfer rate, you can create gear that allows you to perform at your best, even in the worst conditions.



















When shopping for outdoor hiking, there are many factors to consider: the waterproofness and breathability of clothing, its features, and its construction. When choosing outerwear, you want it to keep you dry and warm in rain, snow, and strong winds, and to minimize moisture buildup on the inside of your garment—that's where moisture transfer rate comes in.


What is Moisture Transfer Rate?

Moisture transfer rate is a scientific measurement used to quantify the amount of water vapor or body moisture that can pass through a fabric or garment. When a garment is described as highly breathable, it means that a significant amount of water vapor can pass through it.

Moisture transfer rate is usually expressed in g/m²/24hrs (grams per square meter per 24 hours).

How to Test Moisture Transfer Rate?

The purpose of the Moisture Transfer Rate test for waterproof and breathable outerwear is to simulate the real-world use of a laminate by measuring the ease with which moist air generated by a user's sweat flows from the inside of the jacket to the outside or from one side of the laminate to the other. There are several methods for the Moisture Transfer Rate) test, the most common being the JIS 1099 B1 method (or the inverted cup method). In this method, a cup of hydrophilic desiccant solution composed of potassium acetate is weighed and placed on the surface of the waterproof laminate. The other side of the laminate is in direct contact with water. Because potassium acetate is highly hydrophilic (i.e., attracts water), it draws water vapor from the water bath through the fabric and absorbs it into the potassium acetate in the cup; the increase in the weight of the desiccant solution after a certain time allows the calculation of the moisture transfer rate.

Why is Moisture Transfer Rate Important?

Moisture transfer rate plays a crucial role when purchasing gear for use in harsh weather. This rating tells you how breathable the garment is.

High moisture transfer rate and breathability are two ways users regulate their body temperature. The less moisture trapped inside a jacket, the more comfortable it is. The rapid dissipation of moisture (including sweat) helps eliminate condensation inside clothing, reducing the risk of overheating, cold, and hypothermia.

Furthermore, moisture transfer rate ratings can serve as a guide when shopping, helping you choose clothing suitable for your activities and conditions.