by making the fiber thinner you can increase the amount of dead air space around the fiber. Some superthin fibers are close to the weight of down for an equivalent fiber volume. They stuff down to a small size and have similar warmth-to-weight ratios as down without the wetness issue. Pro: Lightweight and thermally efficient. Good compressibility for stuffing. They do not absorb water and dry fairly quickly. Some fibers are produced in sheets that do not require baffling. Can be stuffed down to a small size. Con: Some are loose fibers that require baffling. Some superthin fibers like Thinsulate are heavy and therefore aren’t good insulators for larger items like parkas and sleeping bags but are very effective in smaller items such as gloves and boots. Examples: Primaloft, Lite Loft, Thinsulate.
Phase Change Materials These materials use tiny spheres or microcapsules either laminated to or embedded within the fabric surface. What is unique about this approach is that the microcapsules can be manufactured to absorb or release heat at a specific temperature. In products designed for cold weather, the microcapsules absorb and retain body heat during periods of activity, and then release the heat back during periods of inactivity—sort of like taking off a layer and putting one back on. For clothing designed for warmer temperatures, the microcapsules absorb body heat, providing a cooling effect. Currently used mostly in gloves and boots. Pro: Absorbs heat to keep you cool in high activity. Releases heat back in low activity. Con: Expensive. Fabric is “tuned” to either cold temperatures or warm temperatures. Example: Outlast.
The Shell Layers
The shell layer consists of an outer jacket and pants layer that protects from wind, rain, snow, and sun. It is essential to have an outer layer that is wind-proof and at least water resistant, if not waterproof. Acting as a windbreaker, the shell layer minimizes convective heat loss, containing the warmth trapped by layers beneath. If your shell layer is waterproof but not breathable, moisture buildup from perspiration is possible, so look for garments that provide ample ventilation options, such as full-front zips and armpit zippers. Waterproof/breathable fabrics provide both wind and rain protection and still allow some perspiration moisture to escape. However, in a driving rain, there is almost nothing you can do to stay totally dry when you are being active. You will either zip up and get moist from sweat or ventilate and get wet from rain, so the goal is to minimize moisture. One thing to think about with shells is sizing—something that fits snugly over a shirt or blouse in the store is not going to work over your wicking layer and two insulating layers. In those cases you need a garment cut large enough to handle most of your inner layers. At the same time, it is not likely that you would buy something so big that you can fit your shell over a down or synthetic parka, so you need to ask yourself if the outer parka also needs to be waterproof.
Wind Shell A wind shell is just that—a shell that projects you from the wind. It is breathable, lets moisture out, and keeps wind out. Typically these are made from fairly lightweight materials such as nylon or nylon blends. They are tightly woven so there are no open spaces for the wind to penetrate. They dry quickly and make excellent outer shells for being active in dry conditions. Pro: Windproof. Allows body moisture to escape. Lightweight. Inexpensive. Con: Not waterproof. Examples: Ripstop Nylon, Pertex.
Soft Shell Soft shells are a step up from a wind shell. These are wind-resistant and water-resistant shells. They are made of synthetic materials with an open weave that allows body heat and built-up moisture from inner layers to escape but is still tightly woven enough to repel light wind and rain. They perform best in active sports where heat production from activity helps draw the moisture out. The heat transfer also works to keep precipitation from entering the fabric. These will keep you dry in “gentle rain” but are not designed to be completely waterproof. They dry quickly and make excellent outer shells. Pro: Wind resistant. Water resistant. Allows body heat and moisture to escape. Lightweight. Dries quickly from body heat. Con: Not completely windproof. Not waterproof. Expensive. If the garment gets totally wet and is in contact with wet inner layers, you can quickly chill from fast water-driven conduction. Examples: Conduit Soft Shell, Polartec Power Shield, Schoeller Dryskin.
Hard Shell Hard shells are waterproof and are designed to keep you dry in pouring rain conditions. There are two approaches to hard shells:
Waterproof Shell These are fabrics that use some type of impermeable waterproof coating (i.e., coated nylon). These will keep you dry from rain but allow water vapor from perspiration to build up in layers underneath. Pro: Very waterproof. Windproof. Inexpensive. Con: Allows for significant body moisture buildup.
Waterproof and Breathable Shell There are a number of ways to make a waterproof and breathable outer shell. All rely on the principle that water droplets from rain are more than 20,000 times larger than water vapor. With a fabric that has a layer with very tiny pores, water vapor can pass through from the inside to the outside while the outside remains impenetrable to water droplets. With all of these fabrics there is always a trade-off between the degree of waterproofness of the fabric and its breathability. Some fabrics use a microporous membrane that is laminated to the fabric (Gore-Tex, Sympatex); others have a microporous coating on the fabric (Ultrex, Triple Point Ceramic, Entrant). Pro: Degrees of waterproofness. Degrees of breathability. Windproof. Con: Degrees of waterproofness. Degrees of breathability. Some body moisture buildup. Expensive.
All hard shells require some form of seam sealing. While the fabric itself may be waterproof, any place where there is stitching means a hole going through the fabric that can let water in. There are a number of approaches to seam sealing including glue, heat sealing, and seam tape.
TRICKS OF THE TRAIL
Bringing Your Rain Gear Back to Life After frequent use, all waterproof and breathable fabrics start to lose their edge. You can revitalize them by washing with a mild nondetergent soap, machine drying, and then lightly ironing the outer fabric on a medium temperature setting. The washing helps restore the membrane or coating’s effectiveness, and the heat of the iron helps bring back the ability to resist water.
Many fabrics (waterproof and waterproof/breathable) have a DWR (durable water repellant) chemical coating on the outside of the fabric. This is what makes water bead up on the surface of your jacket. It’s like your car after a new coat of wax. Over time these coatings wear off, allowing water to seep into the fabric. The garment may still be waterproof, just soaked on the outside and heavier. You can revitalize your DWR finish with spray-on products or by machine-washing it back in with a liquid treatment.
The Head Layer
This is for sun and rain protection, and to reduce heat loss. Up to 70 percent of the body’s heat can be lost through radiation and convection at the head in cold weather. Wearing a hat (preferably wool or synthetic) will conserve heat, allowing the body to send more blood to cold peripheral areas (hands, toes, feet). Other items like wide-brimmed hats can help in a downpour, keep sun off your face, and provide shade to help prevent overheating.
The Hand Layer(s)
These insulate your hands in cold conditions. Gloves and mittens come in all shapes and sizes with lots of different fabrics for insulation. They should fit snugly, not tightly. Gloves provide greater flexibility for your hands, but they are colder than mittens since they have greater surface area at the fingers for radiating heat. A combination of thin synthetic glove liners and fleece or wool mittens is excellent for cold weather. Also good are mitten shells, which add a windproof/waterproof layer. Fingerless gloves or flip-top mittens are great for cooking or other activities that require dexterity.
The Feet Layers
These
