Breathability is the ability of a fabric to allow moisture vapor to be transmitted through the material.
Air permeability is the ability of a fabric to allow air to pass through it. While air permeable fabrics tend to have relatively high moisture vapor transmission, it is not necessary to be air permeable to be breathable.
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.
Also known as JIS L 1099, JIS Z 0208, ISO 2528, Desiccant Method of ASTM E96, JIS K 6328 (JIS is short for Japanese Industry Standards). The A-1 method uses Calcium Chloride solution to simulate sweat while A-2 method uses just water. A desiccant, calcium chloride, is put into a cup. A piece of fabric is then secured over the cup and placed in a controlled environment. 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 show the number of grams of sweat passing through a square meter fabric in 24 hours.
Range | Performance (g m−2 d−1) |
---|---|
Low | <4,000 |
Moderate | 4,000 to 8,000 |
High | >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.
Also known as JIS L 1099 is similar to the ASTM E96-BW test method. A desiccant, potassium acetate, is put into a cup and sealed with a piece of ePTFE (Teflon/Stedfast/Gore-Tex film). The fabric to be tested is then placed over the cup with the fabric side to the cup.
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.
Range | Performance (g m−2 d−1) |
---|---|
Low | <10,000 |
Moderate | 10,000 to 20,000 |
High | >20,000 |
Current upper range is 30,000 g m−2 d−1.
Also known as ISO – 11092 or the Ret or Hohenstein test . In this test, fabric is placed above a porous (sintered) metal plate. The plate is heated and water is channeled into the metal plate, simulating perspiration. The plate is then kept at a constant temperature. As water vapor passes through the plate and the fabric, it causes Evaporative Heat Loss and therefore more energy is needed to keep the plate at a constant temperature. Ret is the measurement of the resistance to evaporative heat loss. The lower the Ret value, the less resistance to moisture transfer and therefore higher breathability.
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.
Range | Performance |
---|---|
Ret 0-6 | Very good or Extremely Breathable. Comfortable at higher activity rate. |
Ret 6 to 13 | Good or Very Breathable. Comfortable at moderate activity rate. |
Ret 13 to 20 | Satisfactory or Breathable. Uncomfortable at high activity rate. |
Ret 20 to 30 | Unsatisfactory or Slightly Breathable. Moderate comfort at low activity rate. |
Ret 30+ | 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.
Ret, A1, B1 and B2 test results do not correlate with each other. Two fabrics may have a B1 of 10,000gr, but one can be 10,000 A1 and the other 4,000 A1. It all depends on the type of coating or lamination and how it moves moisture. Typically hydrophobic coatings perform better than hydrophilic laminations on the Ret and A1 Test. And vice versa, the hydrophilic laminations will perform better on the B1 test.
Below is very generalized positioning of technologies.
Technologies | Ret | B1 | A1 |
---|---|---|---|
Non-coated fabrics | 2-4 | 25,000++ | Not applicable |
MemBrain, and Gore-Tex Pro 2L-3L, Toray Dermizax NX 3L | 4-6 | 25,000+ | 4,000 - 8,000 |
Gore-Tex PacLite, Performance 2L, Entrant HB, PreCip Plus | 6 – 8 | 15,000+ | 8,000 – 15,000+ |
Gore-Tex Performance 3L, PreCip, MemBrain 10, Entrant GII | 7 - 10 | 10 – 15,000 | 5,000 – 12,000 |
Windstopper Softshell, Low end Entrant, most Softshells with film | 8 - 13 | 6 – 10,000 | Not applicable |
Gore-Tex is W. L. Gore & Associates's trade name for waterproof, breathable fabric membrane. It was invented in 1969. Gore-Tex blocks liquid water while allowing water vapor to pass through and is designed to be a lightweight, waterproof fabric for all-weather use. It is composed of expanded PTFE (ePTFE), a stretched out form of the PFAS compound polytetrafluoroethylene (PTFE). Gore-Tex products free of "PFC of environmental concerns" repellent coating lacks the ability to repel oil that "Gore DWR" provided.
A dehumidifier is an air conditioning device which reduces and maintains the level of humidity in the air. This is done usually for health or thermal comfort reasons, or to eliminate musty odor and to prevent the growth of mildew by extracting water from the air. It can be used for household, commercial, or industrial applications. Large dehumidifiers are used in commercial buildings such as indoor ice rinks and swimming pools, as well as manufacturing plants or storage warehouses. Typical air conditioning systems combine dehumidification with cooling, by operating cooling coils below the dewpoint and draining away the water that condenses.
A hygrometer is an instrument which measures the humidity of air or some other gas: that is, how much water vapor it contains. Humidity measurement instruments usually rely on measurements of some other quantities such as temperature, pressure, mass and mechanical or electrical changes in a substance as moisture is absorbed. By calibration and calculation, these measured quantities can lead to a measurement of humidity. Modern electronic devices use the temperature of condensation, or they sense changes in electrical capacitance or resistance to measure humidity differences. A crude hygrometer was invented by Leonardo da Vinci in 1480. Major leaps came forward during the 1600s; Francesco Folli invented a more practical version of the device, while Robert Hooke improved a number of meteorological devices including the hygrometer. A more modern version was created by Swiss polymath Johann Heinrich Lambert in 1755. Later, in the year 1783, Swiss physicist and Geologist Horace Bénédict de Saussure invented the first hygrometer using human hair to measure humidity.
A desiccant is a hygroscopic substance that is used to induce or sustain a state of dryness (desiccation) in its vicinity; it is the opposite of a humectant. Commonly encountered pre-packaged desiccants are solids that absorb water. Desiccants for specialized purposes may be in forms other than solid, and may work through other principles, such as chemical bonding of water molecules. They are commonly encountered in foods to retain crispness. Industrially, desiccants are widely used to control the level of water in gas streams.
Heat recovery ventilation (HRV), also known as mechanical ventilation heat recovery (MVHR) or energy recovery ventilation (ERV), is a ventilation system that recovers energy by operating between two air sources at different temperatures. It is used to reduce the heating and cooling demands of buildings.
Waterproofing is the process of making an object, person or structure waterproof or water-resistant so that it remains relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environments or underwater to specified depths.
Waterproof fabrics are fabrics that are, inherently, or have been treated to become, resistant to penetration by water and wetting. The term "waterproof" refers to conformance to a governing specification and specific conditions of a laboratory test method. They are usually natural or synthetic fabrics that are laminated or coated with a waterproofing material such as wax, rubber, polyvinyl chloride (PVC), polyurethane (PU), silicone elastomer, or fluoropolymers. Treatment could be either of the fabric during manufacture or of completed products after manufacture, for instance by a waterproofing spray. Examples include the rubberized fabric used in Mackintosh jackets, sauna suits, and inflatable boats.
Durable water repellent, or DWR, is a coating added to fabrics at the factory to make them water-resistant (hydrophobic). Most factory-applied treatments are fluoropolymer based; these applications are quite thin and not always effective. Durable water repellents are commonly used in conjunction with waterproof breathable fabrics such as Gore-Tex to prevent the outer layer of fabric from becoming saturated with water. This saturation, called 'wetting out,' can reduce the garment's breathability and let water through. As the DWR wears off over time, re-treatment is recommended when necessary. Many spray-on and wash-in products for treatment of non-waterproof garments and re-treatment of proofed garments losing their water-repellency are available.
Moisture vapor transmission rate (MVTR), also water vapor transmission rate (WVTR), is a measure of the passage of water vapor through a substance. It is a measure of the permeability for vapor barriers.
A vapor barrier is any material used for damp proofing, typically a plastic or foil sheet, that resists diffusion of moisture through the wall, floor, ceiling, or roof assemblies of buildings and of packaging to prevent interstitial condensation. Technically, many of these materials are only vapor retarders as they have varying degrees of permeability.
SympaTex is a type of fabric that is branded as waterproof but "breathable", made or licensed by SympaTex Technologies GmbH a company founded in 1986. The fabric features a waterproof, windproof and breatheable membrane that is laminated to fabrics either on its inner surface or sandwiched between two fabric layers. The latter system offers greater durability, by better protecting the integrity of the SympaTex layer from abrasion to both the outside and the inside of the garment.
Wood drying reduces the moisture content of wood before its use. When the drying is done in a kiln, the product is known as kiln-dried timber or lumber, whereas air drying is the more traditional method.
Robert W. Gore was an American engineer and scientist, inventor and businessman. Gore led his family's company, W. L. Gore & Associates, in developing applications of polytetrafluoroethylene (PTFE) ranging from computer cables to medical equipment to the outer layer of space suits. His most significant breakthrough was likely the invention of Gore-Tex, a waterproof and breathable fabric popularly known for its use in sporting and outdoor gear.
A fabric structure is a structure made of fabric, with or without a structural frame made from the weaving of the fabric itself. The technology provides end users a variety of aesthetic free-form building designs. Custom-made structures are engineered and fabricated to meet worldwide structural, flame retardant, weather-resistant, and natural force requirements. Fabric structures are considered a sub-category of tensile structure.
A thermal wheel, also known as a rotary heat exchanger, or rotary air-to-air enthalpy wheel, energy recovery wheel, or heat recovery wheel, is a type of energy recovery heat exchanger positioned within the supply and exhaust air streams of air-handling units or rooftop units or in the exhaust gases of an industrial process, in order to recover the heat energy. Other variants include enthalpy wheels and desiccant wheels. A cooling-specific thermal wheel is sometimes referred to as a Kyoto wheel.
Interstitial condensation is a type of condensation that may occur within an enclosed wall, roof or floor cavity structure, which can create dampening.
Clothing insulation is the thermal insulation provided by clothing.
Moisture management or moisture-wicking is a functional property in textiles that enables them to transfer moisture from the skin, by capillary action through the fabric, spreading it over a large external surface area, which helps in drying quickly. The property is one of the most important for thermal comfort of textiles.
Textile performance, also known as fitness for purpose, is a textile's capacity to withstand various conditions, environments, and hazards, qualifying it for particular uses. The performance of textile products influences their appearance, comfort, durability, and protection. Different textile applications require a different set of performance parameters. As a result, the specifications determine the level of performance of a textile product. Textile testing certifies the product's conformity to buying specification. It describes product manufactured for non-aesthetic purposes, where fitness for purpose is the primary criterion. Engineering of high-performance fabrics presents a unique set of challenges.
Textile testing is the process of measuring the properties and performance of textile materials—textile testing includes physical and chemical testing of raw materials to finished products.