How do we keep warm in chilly conditions? Add a layer of insulation. Insulating jackets, vests or pullovers are designed to trap body heat, hold it close to our skin and buffer us from colder external air.
Insulation is the middle layer of a 3-layer cold-weather clothing system. Such a layering system involves:
Typical insulation choices:
Most warmth for weight
|Insulation reduced if wet
Slow to dry
Fairly quick to dry
|Potentially wet conditions|
|Fleece||Soft, breathable, stretchy
|Vigorous activity in cool conditions|
Advantages: Impressive warmth for minimal weight. Goose down plumules (a mix of feathers and puffy clusters) exhibit a natural loftiness that is exceptionally efficient at trapping "dead" (noncirculating) air and retaining warmth. Can be compressed into a very small shape. Luxurious feel. Long lasting.
Disadvantages: Loses its warmth-retaining abilities if it gets wet (except for new "water-resistant down" garments). Very slow to dry. Expensive.
Overview: Down garments make an excellent choice for dry, very cold conditions and are well-suited for moderate activity in dry weather such as skiing or snowboarding in powder. Also good for dry, chilly mornings when camping, belaying or backpacking. Relying on down in wet or damp conditions is risky, though; down garments must be carefully shielded from moisture.
Not all down is created equal: Down is graded according to fill power, which indicates how many cubic inches 1 ounce of down occupies when placed inside a container. Down ranges from 450 to 900 fill power. Higher numbers indicate a higher quality of down, with more air-trapping ability. Down with higher fill-power numbers includes fewer feathers and uses bigger, more mature down plumules. Larger down clusters are more durable and can better withstand repeated compressing.
New water-resistant down was first introduced in sleeping bags in 2012 but is starting to appear in outerwear, too. This micro-treatment of down feathers promises to retain down's loft even in wet conditions—a big breakthrough.
Advantages: Water-resistant, will dry much more quickly than down and even retains some thermal resistance when damp. Less expensive, too. The most advanced synthetic fibers (e.g., PrimaLoft) have drawn close to down in breathability, weight, texture and compressibility.
Disadvantages: Down still trumps synthetics in minimizing bulk and weight, though an innovator such as PrimaLoft continues to narrow the gap. Less durable than down, especially if repeatedly compressed.
Overview: A very good insulation choice if wet conditions are expected. It performs quite nicely in dry conditions, too, of course. Personally, I wore a lightweight jacket lined with PrimaLoft during a midsummer climb of 14,411-foot Mt. Rainier and found it to be quite comfortable in what I estimate were 40F (or less) temperatures on the summit. Coworkers tell me they also like synthetic insulation during cool mornings when hiking, camping or sea kayaking. Despite advances, synthetic insulation still can't match high-end down for warmth in extreme cold. Nearly all synthetic insulation is made of polyester.
Like down, not all polyester is identical. The science of synthetic insulation fabrics continues to evolve. At the moment, the PrimaLoft family of insulations (explained in more detail later in this article) is widely considered the most highly evolved "species" of the synthetic world, often besting other synthetics in weight and low bulk, though the differences are not always hugely apparent. Clothing manufacturers routinely create their own proprietary variation of polyester: Coreloft and ThermaTek from Arc'Teryx, for example, Heatseeker (The North Face); Thermal R (Marmot); Thermogreen (Patagonia); and so on. Most of these examples also have a green/eco version, meaning they were manufactured from recycled materials.
Advantages: Very good breathability, making it a good choice when insulation is needed during vigorous, highly aerobic activity. (Down and synthetic jackets/vests are best worn for moderate to sedentary activities.) Dries quickly when wet, usually faster than a puffy-style synthetic garment.
Disadvantages: Not for serious or prolonged cold. While most synthetic fleeces dry quickly, a few are prone to retaining water (and it's not always easy to predict which fleece items are the exception to the dries-quickly rule). Fleece is also bulky and heavy when compared to down and synthetics. Wind can also permeate fleece pretty easily (which leads to chills) unless it contains a wind-blocking membrane (which inhibits stretch) or is worn under a jacket.
Overview: Fleece comes in various weights (light, mid and heavy). Heavier garments, logically, are better suited to colder conditions. Polartec is one of the best-known brand names in fleece. Its Classic fleece categories—100 (lightweight), 200 (mid) and 300 (heavy)—remain popular and are in widespread use. Its Thermal Pro and Thermal Pro High Loft products offer next-generation benefits in terms of lower weight and reduced bulk. Some fleece-like pullovers are specially engineered to provide extra stretch, wind-resistance, water-resistance or some combination of all of these. Ultimately, though, even the heaviest fleece is not as warm as a jacket insulated with down or a synthetic such as PrimaLoft.
A recent trend: Fleece middle layers made out of actual fleece—natural, 100% wool, that is. Already a huge hit with active outdoor types in socks and base layers for its adaptability to cool or warm conditions and its odor-free nature, mid layers made from soft, finely textured merino wool are worth a look. Just be aware that heavier cuts of wool tend to dry slowly. One suggested use is as a downhill skiing layer in dry conditions.
Anticipate the weather. Will you be going out in wet conditions? If you bring a down jacket or vest, be sure to also bring along a weather shield (usually a waterproof-breathable shell) so your down fill stays dry. Alternatively, a synthetic insulation layer offers a little more peace of mind. Regarding temperature, if you're having a tough time deciding between a lighter or heavier garment, usually it's best to opt for the warmer option. This offers greater versatility despite a minor increase in weight and bulk.
Understand the energy output your activity requires. Skiing or climbing in dry, alpine conditions? A puffy down jacket should work beautifully. Hiking in variable conditions? Go with fleece and, for very cool nights at high elevation, consider also toting a synthetic jacket.
Jacket or vest? It's a matter of personal preference. Vests are often preferred by high-energy, high-metabolism types who understand their tolerance for cold and need a just-enough insulation buffer for their core. Get chilled easily? Carry a jacket. A few items, such as the REI Spruce Run Jacket, offers zip-off sleeves, though such sleeves (due to the zippers) are a little bulkier.
Understand your individual variables. Your metabolism may cause you to feel chilly easily. Women often get cold more easily than men; same deal with older outdoor people regardless of gender. Ditto with slender people. In all cases, make sure you choose a garment engineered to keep someone with your characteristics warm
Manage your layers. If you feel too warm during an activity, do not hesitate to open a zipper or strip off a layer. Or reverse those actions when conditions turn cool. Add a cap and gloves when temperatures turn cold.
The remainder of this article features topics that may interest only tech-minded readers, but we think it's worthwhile information to include.
PrimaLoft has emerged as one of the premier synthetic insulations in the outdoor marketplace. Vanessa Mason is the company's global director of business development and the holder of a master's degree in chemical engineering with a specialty in polymer sciences and materials. She addressed a few questions about PrimaLoft's approach to synthetic insulation with REI.com:
Q: PrimaLoft keeps edging closer to down in weight, compressibility and texture. How is that accomplished?
A: It's our fiber technology. It's the size of the fibers, the design or the structure of the fibers, and the types of proprietary treatments we put on our fibers.
Q: PrimaLoft has a good reputation among retailers and in the outdoor media. Yet some shoppers have second thoughts about PrimaLoft because of its relatively thin appearance compared to puffy down jackets. Should they be concerned?
A: That's something people in this industry are educated about—thickness does not necessarily equate to warmth. But it's difficult for some consumers to see that picture. Why does PrimaLoft work? Because it has an extreme microfiber structure. Think of a funnel. With PrimaLoft, you can fit greater number of smaller fibers in that funnel than you can with larger fibers (typical of older synthetic insulations). We just trap more air spaces, so we don't need as much volume to trap as much air.
Q: Is PrimaLoft close to being the equivalent of down?
A: You can get anywhere from 450-fill-power down to 900-fill-power down. Look at pinnacle (superior) down products—900 at the top of the pyramid, 450 and 500 along the bottom. Then look at the pinnacle synthetics, and PrimaLoft One is the best synthetic insulation you can buy. The pinnacle synthetic only crosses over to the down chart near the bottom end of the down pyramid. We usually equate PrimaLoft One as the equivalent of down in the 500 to 550 range. You could not replace a 900-filll-power down garment with PrimaLoft One and expect to get the same performance in dry conditions. However, wet down doesn't even come close to the bottom end of the synthetic pyramid in regard to thermal performance. As soon as you get down wet, you lose a lot of its thermal properties.
Everything in nature moves toward equilibrium. Cold air cools a warm object, and the process works simultaneously in reverse.
Insulation experts like to point out that people don't get cold, they lose heat. Our individual metabolisms create body heat. We lose that heat 4 ways:
By T.D. Wood
Read Author Bio
Last updated: Mon Oct 22 10:49:51 PDT 2012
In This Article
How are we doing? Give us feedback on this page.