Collins Complete Hiking and Camping Manual: The essential guide to comfortable walking, cooking and sleeping. Rick Curtis
(Goose down is finer quality than duck.) Down is rated by its fill power, or how many cubic inches of volume an ounce of down will fill. Fill power goes from 550 cubic inches up to 800—a 700-fill sleeping bag lofts better and is more thermally efficient than a 550-fill bag. Most high-end sleeping bags are made of 700 fill; 800 fill is mostly for expedition-quality garments and sleeping bags.
Since down is a loose fill, sleeping bags and clothing must have a series of small compartments sewn in with baffles to hold the fill evenly throughout, which adds to the manufacturing cost. Down is useful in sleeping bags since it tends to conform to the shape of the occupant and minimizes convection areas. It is also very compressible, which is an advantage when packing. But the same compressibility means that your body weight compresses the down beneath you, significantly reducing your insulation from the cold ground, so you need an insulating pad underneath you more so than with a synthetic bag. Pro: Excellent insulator. Incredible warmth-to-weight ratio. Compresses to extremely compact size. Long life span if cared for properly (up to 20 years). Con: When down gets wet it simply clumps together and loses almost all of its insulative value and is almost impossible to dry in the field. Use depends on your ability to keep it dry. When using a down sleeping bag, take special care to prevent it from getting wet. For example, a vapor barrier sleeping bag liner in a down bag will help the bag stay dry from the inside and a waterproof-breathable bivy sack will help the outside keep dry. Keeping the bag in a waterproof stuff sack will protect it during the day. In wet conditions a down-fill outer parka may get soaked, and a synthetic-fill would be better. Down is a loose fiber fill that requires baffles (see “Tricks of the Trail,”.) Expensive. Some people are allergic.
Synthetic Fibers There is a multitude of different synthetic fibers used for garment and sleeping bag fills. Most are based on some form of polyester. These are primarily used in sleeping bags and heavy outer garments, like parkas. The fibers are fairly efficient at providing dead air space (though not nearly as efficient as down). Some products like Polarguard are made in large sheets. Others create additional dead air space by having hollow channels within the fiber (e.g., Quallofil). Pro: They do not absorb water and dry fairly quickly. Some fibers are produced in sheets that do not require baffling. Con: Heavy. Not as efficient an insulator as down. Hard to compress to a small size. Some are loose fibers that require baffling. Fibers produced in sheets tend to break down over time, losing their loft more quickly. Examples: Polarguard 3D, Polarguard Delta, Quallofil.
“Superthin” Fibers These synthetic fibers are based on the principle that 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.