How to Choose Insulated garments
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. But with Down and Synthetic wadding combined with a shell fabric can be an outer garment.
- Base layer such as a T-shirt or long underwear.
- Insulation layer such as a fleece jacket or down vest.
- Outer layer (weather-resistant shell) such as a rain jacket. Outer layers may also be insulated.
Typical insulation choices:
- Down: nature’s best insulator.
- Synthetic fibres: engineered to mimic down’s natural loftiness.
- Fleece: usually made from synthetic fibres, though some wool jackets/sweaters exist.
Most warmth for weight
|Insulation lost if wet
Slow to dry
|Dry conditions like high altitude or polar conditions.
Fairly quick to dry
|Potentially wet conditions
|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” (none circulating) 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. 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. (In lab testing, the typical container is a tube.) 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.
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 fibres (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. 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 excelling other synthetics in weight and low bulk, though the differences are not always hugely apparent.
Polar Fleece fabric is construction contains many air pockets that work to trap warm air created by the body, insolating you and keeping you warm. The open knit construction allows air circulation and moisture to move away from the body by convection, which keeps you dry and comfortable during you activity.
History of Fleece
Malden Mills‘ original fabric was revolutionary because it was both lightweight and warm. It picked up less than 1% of its weight in moisture, and even when completely wet, it maintained its loft and insulating properties. It made an ideal outerwear fabric because it actively wicked moisture away from the body.
Today the term polar fleece is applied to a class of high technology, high performance products that offer tremendous warmth relative to their weight, that are soft to the touch, and that are able to wick moisture away from the body so that they feel dry even when soaking wet. This class of fabric includes both fleece and pile fabrics, even though the two fabric types are constructed differently.
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, and maintains its loft under waterproof garments.
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 synthetic insolation wadding. 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. It’s 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 odour-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 an alpine skiing insulation layer in dry conditions.
Buying and Wearing Tips
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.
Understand your individual variables. Your metabolism may cause you to feel chilly easily. Women often get cold more easily than men; older outdoor people regardless of gender, also 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 I think its worthwhile information to include.
A Closer Look at PrimaLoft
Q: PrimaLoft keeps edging closer to down in weight, compressibility and texture. How is that accomplished?
A: It’s our fibre technology. It’s the size of the fibres, the design or the structure of the fibres, and the types of proprietary treatments we put on our fibres.
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 fibres in that funnel than you can with larger fibres (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.
Understanding Heat Transfer
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:
- Conduction: Occurs through the surfaces we touch, particularly the ground below us. Ever sit on a snow drift or a block of ice? That chill you felt on your back side was heat loss caused by conduction.
- Convection: Air circulation carries away body heat. Think about standing outside on a 20F day while wearing fleece. Now think about the same day with a 20 mph wind. The cold air will blow through the fleece and displace the warm air, causing your body temperature to drop unless you add a shell. The shell by itself does not add any insulation, but does cut the wind. That cuts heat loss due to convection. Convection requires moving air. Air temperature alone does not cause convection; that would be conduction. The cold air temperature will cause your body temperature to drop unless you bundle up.
- Radiation: Our bodies are heat-generating machines. When our activity level slows, so does our heat-making ability. Radiation is why your face feels warmer than your back when looking at the sun. The air temperature is the same, but the radiant heat from the sun warms you. The opposite is also true when looking at space at night. This is why it is warmer to sleep under a leafy tree. Radiation is a complicated subject; even for engineering students find it to be a difficult concept.
- Evaporation: When we sweat, the moisture’s evaporation cools our skin. This is good when we’re warm, but less than ideal when active in cold conditions. Of course, humans are exhaling moisture and evaporating moisture from our skin all the time, not just when sweating. It’s just more noticeable during activity.
The Curious CLO
Home insulation is measured by a calculation known as R values. Garments have something similar, a lesser-known metric known as a CLO value. Believed not to be an acronym but simply a truncated version of the word “clothing,” CLO values were hatched in the 1940s and still used to gauge the effectiveness of insulated garments today, though they are rarely presented to consumers.
The CLO benchmark is 1.0, considered to be the amount of clothing necessary for an inactive human to feel comfortable at room temperature, which is considered to be 21C, or roughly 71F.
How much clothing is that? A fully dressed men’s business suit, of all things: shirt, tee, pants, jacket, socks, shoes. (Interestingly, the fabric of the suit was never mandated—just “a business suit.”) Consumers rarely see CLO numbers referenced on promotional materials.