As part of your gear for hiking, climbing and mountaineering it is essential that your garments be breathable – otherwise your sweat will accumulate inside them, leaving you clammy and miserable.

Four types of waterproof and breathable fabrics commonly found in outdoor clothing are GORE-TEX, eVent, Polartec Neoshell and Pertex Shield.

Sweat permeability

At peak activity levels, your body relies on evaporative heat loss as its primary means to combat overheating. When this process is hindered by impermeable clothing or materials that do not permit airflow close to the skin and allow sweat evaporation, discomfort and cold can quickly set in. Breathable fabrics allow airflow close to your skin allowing sweat evaporation for comforting cooling effects that keep you relaxed and comfortable during physical exertion.

Waterproof breathable fabric technology first popularized by GORE-TEX jackets in 1978 is designed to block rain while still allowing sweat vapor to escape through its membrane or coating. Today, many brands now offer waterproof jackets and pants made with polyurethane or polyester membranes; some even achieve an MVTR Upright Cup score which rivals that of GORE-TEX jackets!

Some fabrics employ physical ventilation features like mesh areas to accelerate wicking processes and avoid condensation build-up, or back vents with flaps that allow air out while keeping water out, or zipper off sleeves that can be opened when not necessary.

Water permeability

Breathability (water vapor permeability ) allows sweat from your body to escape during active use and helps clothing remain dry. A higher breathability also ensures greater comfort.

Most waterproof breathable jackets utilize a membrane or coating that blocks raindrops from entering, while their outer face fabric features durable water repellent finishes to protect it against raindrops soaking through and diminishing breathability.

Permeability in waterproof breathable jackets depends on the relative sizes of pores within their membrane or coating and water molecules and raindroplets that pass through it. Most PTFE and PU membrane pores have diameters ranging between 0.1-10 microns while water vapour molecules and raindroplets typically have much larger dimensions.

Some fabrics boast very high permeation rates, such as eVent and Neoshell; others, such as Victorian Mackintosh made of rubber sandwiched between cloth, have low permeance. Outdoor enthusiasts favor The North Face’s FUTURELIGHT fabric featuring a PU membrane which boasts a reported waterproof rating of 10,000mm with exceptional breathability ratings.

Heat permeability

Breathable fabrics allow air flow close to the skin, helping prevent heat build-up and keeping us feeling cool and comfortable on hot days or during strenuous activities like climbing or running. Breathability is particularly useful on days that reach extreme heat or during activities like climbing and running which require exertion.

Breather fabrics can help regulate body temperature by allowing sweat to escape the surface of the fabric quickly, quickly dissipating into the surrounding air where it can evaporate more readily.

Since GORE-TEX jackets first entered the market in 1978, waterproof/breathable technologies have advanced significantly and become readily available across a range of price points. While ePTFE membranes like those found in GORE-TEX and Patagonia Houdini jackets remain the go-to for waterproof/breathable properties, high performance polyurethane and polyester membranes have made significant inroads into the industry as well.

Brands often tout their rain gear’s breathability, yet it’s important to understand their testing methodology and results. Many test results vary between brands, and don’t translate directly to real world applications.

Comfort

Breathability can play an essential part in your comfort and performance while hiking, mountain biking, skiing or engaging in any outdoor activity. Without breathable clothing, your body could generate excess heat and moisture that is trapped against your skin, leading to discomfort or chills. But with the appropriate gear – for instance choosing jackets with high breathability ratings will help prevent sweat build-up by enabling airflow around you allowing sweating as it releases excess heat – these unpleasant side effects won’t come into play during outdoor adventures!

For more strenuous outdoor pursuits, it is wise to wear waterproof breathable clothing. These garments provide both breathability and waterproof protection – ideal for snowy and rainy conditions alike. A ski jacket designed with waterproof shoulder panels while remaining highly breathable elsewhere makes an excellent mountainous companion.