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Why is a Hard Shell Necessary?

We are often warned of weather's ability to suddenly change when out in the mountains or on a hike in the woods. If you happen to be unprepared when the weather does change suddenly, wind and rain can quickly turn a pleasant outdoor hike into a miserable shivering experience. Soaked clothing won't just ruin your hike, this situation is potentially very dangerous. As your body's temperature lowers, your risk of hypothermia increases. Hypothermia is the condition in which core body temperature drops below 35°/95°F. It can result from exposure to cold weather, a decrease in heat production, or increase in heat loss. Hypothermia can lead to shivering and stumbling, and if the condition worsens, you may have difficulty moving on your own, become unable to speak or speak incoherently, and it is possible to lose consciousness. If left untreated, hypothermia can even lead to death. We often see the phrase "froze to death" in the news and reports about hiking accidents, but this does not mean it was so cold out that a person froze. Death results from a lower body temperature that causes the body to shut down. Many people think that hypothermia is more likely to occur during cold winters and the reality is that the periods between spring and fall, when people are more likely to encounter wind and rain while outdoors, are more likely to lead to rapid loss of body temperature. Older individuals are particularly susceptible and should be careful of such conditions, as their bodies are less able to feel differences between hot and cold and have a greater difficulty regulating their body temperature.


--- Stopping water from getting in ---

Waterproofing is a measure of the ability to resist pressure from external moisture trying to permeate into a material. This property can be described with a numerical value that measures "water pressure resistance." Water pressure resistance is measured by placing a column of water on the outside layer of a material and applying pressure until water begins to seep through, at which point the height of the water is measured in millimeters.

So then, just how much water pressure resistance is needed from a hard shell?

Most standard windshells, a common outer layer, only have about 300mm of water resistance, making them suitable for light rain for a short period of time.

Without even realizing it people apply extremely high levels of water pressure to their clothing. To give an example, sitting down on a wet bench places about 2,000mm of water pressure on the seat of your pants. Can you imagine what kind of water pressure you place on your pants when you bend down on one knee or how the weight of your backpack affects your jacket? A hard shell requires water pressure resistance far beyond that offered by a standard windshell.

Montbell's hard shells offer 20,000 to 45,000mm of water pressure resistance, meaning they are well equipped to handle even extreme outdoor conditions. They also have features such as the Aquatec Zipper, a water resistant zipper that eliminates the need for storm flaps, and seam taping to protect against water leaking through the fabric's seams.

All models are subjected to storm testing to ensure that water does not leak through.


--- Allowing trapped moisture to escape ---

Is a high level of water resistance the only feature your hard shell needs? Vinyl raincoats certainly have a very high degree of water resistance, but they cannot release heat or water vapor that builds up inside. Similar to windows on a cold winter morning, water vapor can cool and condense into water droplets on the inside of your jacket. So even if your hard shell is able to protect you from external moisture, if it can’t release water vapor, you can still get wet from internal condensation.

Breathability refers to a material's ability to release built up water vapor. GoreTex Fabrics and other membranes make this possible by keeping water from getting in and allowing water vapor to get out. Membranes can do this because liquid water molecules (rain) are larger than vapor molecules (evaporated sweat), which allows vapor molecules to escape through the membrane's microscopic openings. (left figure, excluding certain materials.)

What an outer layer truly needs is "waterproof breathability," a high degree of water resistance combined with the ability to let out internal moisture.

Water Repellency

--- Preventing fabric saturation ---

A good example of water repellency is how water balls up and rolls off of a leaf. Water will always try to stay in a spherical shape due to surface tension. When water comes into contact with the surface of your jacket, this spherical shape will break down and the water spreads out. If the surface of your jacket has a durable water repellent (DWR) treatment, bar-shaped water repellent molecules stick up from the fabric allowing water to maintain its spherical shape and simply roll off your jacket.

The terms "water repellent" and "waterproof" are often confused and used interchangeably. This is due in part to the various water repellent sprays that are on the market. Most products that call themselves "waterproof", are in fact, "water repellent". These sprays can give cotton t-shirts water repellent qualities for a short amount of time, but they cannot make that same cotton t-shirt waterproof. These sprays may stop a fine mist from seeping through, but spilling a drink on the same cotton t-shirt won’t have the same effect as the treatment has very low level of water resistance. In other words, clothing that is only water repellent cannot completely stop rain or snow.

Water repellency affects a garment's breathability. The more your garment is worn, the more its DWR treatment is affected by dirt and friction. When a garment's DWR treatment becomes worn down, water is able to spread out over the fabric's surface, saturating it and blocking the membrane's pores. With the pores blocked, water vapor trapped inside is unable to escape. A hard shell with no water repellency can become saturated with water, becoming heavy and rob the body of its heat due to water's high thermal conductivity.

Maintaining a hard shell's performance

Although the performance of a hard shell's waterproof breathable membrane won't degrade over time, DWR treatments will degrade. Therefore, maintaining a garment's DWR treatment is essential maintenance for the overall performance of your hard shell.

A hard shell's DWR treatment degrades the more it is used. On a microscopic level, when a DWR treatment is functioning properly, the bar-shaped water repellent treatment stands up in well-aligned rows. When these rows become disorderly and unaligned, water droplets lose their surface tension and spread out over the surface of the fabric.

When you start to notice that rain no longer beads off of your hard shell and the outer fabric is instead absorbing water, please see our maintenance and care page for more information on retreating your hard shell.

Choosing the right hard shell

Waterproof breathable fabric begins as an extremely thin membrane, which is then sandwiched between an outer fabric and inner fabric to protect it. For hard shells, even if the waterproof breathable membrane is the same, differences in thread thickness and weave used in the outer and inner fabric can affect the durability and weight of the item.

Montbell designs our hard shells with a variety of materials and features to meet the demands of the hot and humid climate of Japan. In addition to making products with GORE-TEX, Montbell also has designed our own proprietary waterproof breathable membranes; DRY-TEC, Breeze DRY-TEC and Super Hydro Breeze.

For example, take the following two products in the Montbell hard shell lineup. Both are designed with similar weights and features, and both jackets are designed for superior comfort when conditions become less than favorable. However, there are differences in foul weather performance. The GORE-TEX Storm Cruiser offers more than twice the water resistance of the DRY-TEC Peak Shell when comparing water column results.


GORE-TEX fabrics are perfect for highly aerobic sports that require the ultimate in waterproof / breathable technology. GORE-TEX fabrics are available in 3-layer and 2-layer constructions.

The full coverage Storm Cruiser Jacket, utilizing the uniquely soft GORE C-KNIT Backer Technology, is light weight and dependable. By incorporating the C-Knit concept this rain jacket becomes supple, quieter, and far more comfortable that previous Storm Cruiser models. The extremely thin, yet densely circular knit backing is bonded to the GORE-TEX membrane, making a laminate that is 10% lighter and 15% more breathable than previous GORE-TEX constructions.

GORE-TEX, GORE and designs are trademarks of W.L. Gore & Associates.


Developed by Montbell, DRY-TEC is a 2-ply waterproof/breathable fabric that's very soft and comfortable. We begin by laminating fabric to a microporous membrane that is only 25 microns thick. The micropores of this super-thin membrane make the fabric impervious to liquid water but still allow water vapor molecules to pass through. The laminated membrane is then coated with polyurethane coating and finished with a hydrophilic coating designed to wick moisture away from your skin. The polyurethane/hydrophilic coating makes up the second layer of 2-ply DRYTEC.

The Rain Trekker Jacket utilizes DRY-TEC in combination with our Dry Lining Technology to increase comfort and create a quieter jacket. Dry Lining Technology is a woven polyester lining designed to dry quickly and feel comfortable, even next to skin, no matter your level of activity. This woven lining, rather than a knit lining, also aids in making the Rain Trekker Jacket as light as possible.