Product Code Database
Breathability is the ability of a fabric to allow moisture vapor to be transmitted through the material.
Moisture Vapor Transfer (MVT) in waterproof fabrics occurs by two processes:
Driving Force is the difference in the level of heat and humidity on one side of the material compared to the other side. Also known as the Differential Pressure. By the second law of thermodynamics moisture will move towards dry. Therefore, warm, moist air will flow towards cold, dry air until there is an equilibrium.
Due to body heat and moisture there is almost always higher heat and humidity inside a clothing system. This creates a differential pressure forcing the heat and humidity toward the outside. The greater the difference between the heat and humidity inside the clothing system and the outside, the greater the Differential Pressure to push that heat and humidity out.
| <4,000 |
| 4,000 to 8,000 |
| >9,000 |
Typical maximum with current technologies are in 15,000 range. High-performance fabrics may get A1 test scores in 10,000 to 15,000 g m−2 d−1 range and usually shows that a fabric has a fairly quick release of moisture, but may not be the best over longer periods of use.
The cup is then inverted into a pan of water. Then after period of time the cup is weighed to see how much water has been “pulled” into the cup through the fabric. The weight is then extrapolated to yield the number of grams of fluid passing through a square meter of fabric in 24 hours.
The B-1 variant of test method puts membrane in direct contact with water while B-2 variant adds an ePTFE film between the water and the fabric. While B-2 is a good test, it eliminates the effect of fabric when in direct contact with water. When sweat condenses on the inside of a fabric with a hydrophilic laminate, the lamination will actively pull the water through the fabric reducing condensation. This can be a tremendous addition to the comfort of the user. The B-2 test is also best used for non-waterproof fabrics, so the water in the pan does not pass directly through the uncoated fabric.
| <10,000 |
| 10,000 to 20,000 |
| >20,000 |
Current upper range is 30,000 g m−2 d−1.
Hohenstein added a unique aspect to their testing. They had real people wear garments made with the fabrics of varying Ret values and work out on a treadmill. They gathered the comments of the testers and correlated this to the Ret values of the fabrics and came up with a Comfort Rating System.
| Very good or Extremely Breathable. Comfortable at higher activity rate. |
| Good or Very Breathable. Comfortable at moderate activity rate. |
| Satisfactory or Breathable. Uncomfortable at high activity rate. |
| Unsatisfactory or Slightly Breathable. Moderate comfort at low activity rate. |
| Unsatisfactory or Not Breathable. Uncomfortable and short tolerance time. |
The testers could not perceive a difference in the garments made with fabrics within these ranges. So, a garment made with a 40 Ret fabric and one made with 55 Ret fabric did not have a perceivable comfort difference in use.
| Not applicable |
| 4,000 - 8,000 |
| 8,000 – 15,000+ |
| 5,000 – 12,000 |
| Not applicable |
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