Waterproof Breathable Clothes - Types and Performance
In our post about waterproof breathable fabrics (WBFs), we emphasized the importance of this kind of textiles for sportswear and underlined their main functions, properties, and applications. We also presented the current trends and future projections of their use. We also mentioned various clothes made of waterproof breathable materials such as rain jackets and the reason why they’re so important for outdoor enthusiasts and professionals.
More and more people engage in and enjoy outdoor sports and activities. There are various reasons for the increasing popularity of outdoor pursuits, but among the most important ones are the excitement, the challenges, and difficulties under various environmental conditions as well as the opportunity to spend some time outdoors and reconnect with nature. Since both the environment and the heat generated by activities are beyond the control of the person engaged in the outdoor sports, it is important to provide people with reliable sportswear ready to meet the challenges of rough terrain and/or bad weather. For maximal enjoyment, this clothing must provide both protection from the environment and comfort. It normally forms a layered clothing system, suitable for various activities to be undertaken in various environmental conditions.
Layering is among the most important concepts regarding outdoors apparel. A layered clothing system usually consists of three layers of clothing, each with its functions: a wicking and quick-drying base layer, a breathable mid layer to trap still air next to the skin for better thermal insulation, and a wind- and water-resistant outer layer for maximum protection from the elements. For complete protection from rain or water, it is possible to wear a fully waterproof jacket. However, as we explained in All About Waterproof Breathable Fabrics, the use of a simple waterproof outer layer is ineffective because it shields from rain and snow but it doesn’t let internal water vapor to escape. This leads to a formation of condensation in the clothing system which seriously decreases the system’s capacity for ensuring insulation and weather protection. Moreover, this leads to the feeling of clamminess and what’s worse - to excessive cooling. Therefore, to provide both protection and comfort to the user, the outer layer must be waterproof and breathable.
Types of waterproof breathable clothes
The intense effort during sports leads to increased sweating, thus the waterproof breathable clothing intended for sportswear needs to be functional enough to ensure a higher moisture transfer rate from the body towards the exterior. In addition, it needs an appropriate design and the use of special manufacturing methods engineered towards guaranteeing that the sportswear will retain its waterproofness and durability during wear.
Seams are one of the weakest spots of waterproof clothing as a failure of the seams can threaten the performance of their waterproofness. Main reasons for this are wear and tear as they can quickly degrade the seams. This can be avoided by changing the type of the seams and/or the method of sealing the seams. Unfortunately, many manufacturers do not seal all seams but restrict sealing to the most vulnerable seams such as shoulder seams and side seams. They do that by using specific tapes (welding heat-seal tape is among the most popular types of sealing) for sealing the seams to avoid their failure.
The most popular choices for rain gear are jackets and pants made of waterproof breathable fabric.
Rain pants are generally made of nylon (or nylon blends) and waterproof breathable fabric. When buying a pair of rain pants, there are two important things to check: their functionality and the fit. They need to be wind-resistant and stretchy or loose fitting for freedom of movement since they will probably be worn over other pants. There are two basic designs: simple pants and bib pants.
Bibs are bulky and heavy and have a high back and chest and suspenders. They are not suitable for summer trips - their best use is for cold weather expeditions. They cover much of the torso for two main reasons - this way they keep you warm and minimize the chance that snow will get into your clothes.
Simple pants are cheaper, lighter, less bulky, and easier to get on and off than bib pants. They’re more versatile and are suitable for milder conditions (some types are actually ultralight, however, they are not suitable for continuous use because they are too fragile). For summer hiking, neither of these is better than a pair of shorts or synthetic pants as they’re light, relatively warm, and dry quickly when damp.
Some of the most desirable features of rain pants include:
- Adjustable drawcords and cord locks for individual fit and to seal warmth in.
- Full-length zippers for getting the pants on over boots, crampons, skis, snowshoes, and for ventilation.
- Reinforced knees for added durability.
- Pockets for storing small personal items. Big pockets can hold a map, while zippered pockets are suitable for storing documents and money.
- Length - rain pants need to fully cover your base layer pants underneath. In very cold weather, you may prefer wearing fleece pants for better insulation, while in warmer weather it makes sense to choose thinner and lighter pants.
- Weight depends on design and fabric. Generally, heavier garments are more durable and will outlast lighter ones.
It takes time and practice to adjust clothing, so experiment donning and doffing it when necessary to keep from overheating, or from getting too cold.
The outer layer should provide protection from wind and precipitation so you need to choose your rain jacket wisely keeping in mind that you must find one with the right balance between weight and functionality.
The ideal shell is lightweight, windproof, fully waterproof, and completely breathable, and… it doesn’t exist because there is no garment that can achieve all these objectives. Many passionate outdoorsmen carry two different shell layers - a lightweight windproof shell and a lightweight waterproof jacket. The reason is simple - it’s barely impossible to find one piece of garment that’s fully waterproof, completely breathable, and wind-resistant at the same time. You can be more flexible by carrying such a system with two different outer layers. Rain shell is usually worn only in heavier rain or for periods of low-intensity walking, while breathable wind gear is worn in cool and windy conditions, and for periods of heavy exertion.
Typical Waterproof Breathable Jacket Design
Source: High-Performance Apparel*, p.446
Rain jackets come in different styles and designs. Good jackets feature bonded watertight full front zippers and are easier to ventilate; they are large enough to handle most of your inner layers without restricting mobility; armpit zippers are typical as they allow for ample ventilation - aim for such models where you will be able to zip or unzip the underarm vents during movement with one hand only; seams must be properly sealed; bonded zippers and zipper garages keep the zippers dry; adjustable hems and sleeve cuffs add more functionality because they keep the cold out and offer more precise fit; a drawstring hood with adjustable pull wards off rain and provides protection from wind. In addition, large zippered side-entry pockets are easily accessible and useful for maps, hats, gloves, and other small personal items.
Keep in mind that in driving rain, you cannot stay completely dry on the trail no matter what you do - you will get some moisture, for sure, either from sweat (if you zip the rain jacket) or from precipitation (if you unzip to ventilate). However, you should do whatever is possible to minimize moisture.
The best way to maintain the functionality of a rain shell is to use it only when it is really needed. Rain jackets depend on waterproof breathable membranes or coatings that are too delicate. For example, breathability is reduced when fabric pores get clogged up with dirt and sweat. Thus, you need to: keep the shell clean (always follow the manufacturer’s instructions for proper maintenance of the garment), and maintain the quality of the water-repellent finish applied on the shell surface. When you notice that the DWR on your rain jacket is falling, restore it with a wash-in or spray-on treatment. The outer layer of your rain jacket must be water-resistant in order to maintain the garment’s breathability. The reason is that the DWR finish causes water to bead on a fabric surface without impairing breathability. As the finish degrades, the fabric becomes no different than a regular non-treated fabric - it gets saturated with moisture which seriously reduces breathability of the rain shell. That's why you need to reproof the garment regularly.
Waterproof breathable fabrics are laminates, consisting of up to three distinct bonded layers. 3-layer constructions are the most waterproof and most durable, but also heaviest and least breathable. Such constructions often look the following way:
- Face fabric treated with a DWR. It’s usually made of nylon or polyester and is expected to be durable. In general, the thicker the fabric, the more durable the garment.
- Waterproof breathable membrane.
- Lining protects the membrane from abrasion and pore-clogging contaminants such as body oils.
There are three main types of constructions.
Arrangement of individual layers in WBFs and application in outdoor jackets
Source: Waterproof and Water Repellent Textiles**, p.62
These are the original waterproof breathable constructions. Each 2-layer construction is a laminated product with a DWR-treated face fabric and a waterproof breathable layer. The linings are often warp-knitted mesh constructions (to promote airflow) attached by a separate fabric or mesh liner that hangs inside of the garment. PU coating at the hem and cuff prevents rain wicking into the interior of the garment.
- Lowest price in comparison with the other types of laminates
- Extra weight due to the added layer
- Reduced breathability because of the liner
This type of construction is prevalent in light-to-medium-weight garments for skiing, hiking as well as casual and fashion jackets, and some rain pants.
Their construction is very similar to the construction of the 2-layer laminates, as the main difference is that the protective fabric or scrim gets eliminated in exchange for a printed or sprayed-on partial protective layer. It provides a barrier between the laminate and the skin or other clothing layers.
- Lightest type
- Relatively low cost
- Reduced breathability because of the protective layers
2.5-layer laminates are used mainly for lightweight and ultralight rain clothing. They’re suitable for intensive outdoor activities such as fell running and mountain biking.
They comprise three layers as described above. A waterproof breathable membrane is glued between the face fabric and a soft lining to produce a material that is hardwearing but slightly stiff. This is the most durable of all three types of laminates described here because the membrane is protected by fabric on both sides. It is developed for the needs of alpinists and other outdoor enthusiasts who are in a need of hard-wearing waterproof breathable garments.
- Most expensive type
- Lower breathability than the 2-layer construction
- Least flexibility
3-layer laminates are widely used in the top range of outdoor sportswear. Garments incorporating these fabrics are promoted as exclusive high-performance shells.
We described the main principle of how WBFs function in our post about waterproof breathable textiles. In short, their functionality depends on the relative humidity levels: moisture wants to establish an equilibrium that’s why if it’s more humid inside the garment, moisture will move outward and the opposite.
The first two tables below show fabric waterproofness and breathability ratings together with a brief explanation of the practical meaning of these ratings. Table 3 shows the heat energy produced by various activities and the corresponding perspiration rates related to these pursuits.
Table 1: Fabric waterproof ratings
Table 2: Fabric breathability ratings
Table 3: Heat energy produced by various activities and corresponding perspiration rates
Source: Waterproof and Water Repellent Textiles, p.32
Several studies have shown that waterproof breathable fabrics can be ranked according to their capacity to transfer water vapor to the ambient environment. These agree that ePTFE laminated membranes are most permeable, followed by hydrophilic and PU microporous laminates and then PU coatings. However, even the capacity for moisture vapor transfer through ePTFE membranes is limited as Table 3 shows. It confirms that water vapor cannot be completely diffused despite the manufacturers’ claims about the breathability of their products. Moreover, rain and snow reduce breathability further because the vapor pressure above the fabric is increased. Additionally, in prolonged precipitation as well as in cold weather (because of condensation), pores on the fabric can get clogged. Therefore, you should expect the breathability of a rain jacket or rain pants to be compromised in the field, mostly by moisture, but also by dirt, and body oils.
What are the waterproofness and breathability ratings of today’s sportswear? First, let’s begin with the fact that manufacturers use different numbers to label their products “waterproof” so it can be really hard to compare two “waterproof” garments from different producers, especially if their ratings are not publicly announced as often happens. However, any garment with a rating of 20 000mm or more is acknowledged to be fully waterproof. The situation with breathability ratings is worse because different manufacturers often use different methods to measure breathability. Moreover, various test methods use different temperatures or humidity conditions and can give vastly differing values. By the way, nowadays, you will rarely see any breathability ratings on the labels of the garments.
What most people don’t know is that despite the fact that there are various names, brands, and garments on the market, the number of WBFs manufacturers is far smaller. Nowadays, the waterproofness of most products falls within 8000-28 000mm water column per 24 hours, while the range of breathability is between 5000g/m2 and 30 000g/m2 per 24 hours. Just for a reference, 20 years ago, the breathability of the then modern WBFs was no more than 10 000g/m2.
Although we didn’t call all types of waterproof breathable clothes in this article, you should know that there are various types of WB garments besides rain jackets and rain pants.
There are various constructions of waterproof breathable fabrics available on the market. Some of the most widely spread constructions are 2-layer, 2.5-layer, and 3-layer laminates. Each one has its own pros and cons related to its durability, breathability, weight, compactness, and price. Waterproof breathable constructions are used extensively in sports products especially to provide protection from the elements for hikers, mountaineers, cyclists, sailors, and other outdoor professionals and enthusiasts. Recent years have seen significantly increased participation in outdoor sports and activities so manufacturers offer different grades of fabrics suited to different performance requirements.
The technology behind designing WBFs and clothes has continued to evolve for achieving improved functionality. However, there is still significant potential for further developments.
* In J. McLoughlin, & T. Sabir (Eds.), High-Performance Apparel: Materials, Development, and Applications, 2018, Elsevier Ltd.
** In J. Williams (Ed.), Waterproof and Water Repellent Textiles and Clothing, 2018, Elsevier Ltd.