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All About Fleece Jackets

Everyone's Favorite Midlayer

Not all fleece jackets are created equal.

Differences in synthetic and natural fibers, fleece weights, and jacket features make for a range of possibilities when choosing a fleece jacket. Here’s the lowdown on this popular midlayer.

Enter Synchilla

In 1985, Patagonia released its first Synchilla fleece jacket, a mass-produced, synthetic fiber, midlayer insulating piece that was quick drying, packable, and lightweight, an excellent alternative to the badly pilled powder-blue-and-tan pile sweaters common in the early ’80s, or the traditional water-absorbing wool, down, or cotton layers that dominated mountaineering clothing in the decades before. Synchilla was the product of years of collaboration between Patagonia’s Yvonne Chouinard and the now-defunct Malden Mills, which in 1979 invented Polar Fleece, the mother of all technical synthetic fleeces. Synchilla jackets, produced in vivid colors and mass quantities, ignited a trend that reached into the world beyond the mountaineering community.

Malden Mills’ former CEO Aaron Feuerstein initially declined to patent Polar Fleece, allowing the material to be produced cheaply and widely by multiple companies. Over the next 20+ years, synthetic fleece jackets took on a brace of design features that made “fleece” the preferred midlayer for mountaineers, climbers, skiers, backpackers, fly fishers, and just about every other sort of outdoor enthusiast. Companies like The North Face and Patagonia were soon selling millions of units in the developed world, and fleece jackets also took hold in markets beyond outdoor sports.

The Advantages of Fleece

“Fleece” is a soft-napped, insulating fabric made from polyethylene terephthalate (PET), a hydrophobic fiber first used in waterproof ropes. Hydrophobic fibers repel water, meaning fleece holds less than 1% of its weight in water, retains much of its insulating properties when wet, and is highly breathable, lightweight, machine-washable, and quick drying. Fleece also doesn’t itch, feels warm, can be produced in almost any color or pattern imaginable, and is just as comfortable in the backcountry as on the couch.

The Disadvantages of Fleece

Because it’s hydrophobic, fleece resists soaps and detergents, but not bacteria, making it prone to mountaineerish odors. Also, fleece is fleecy, so it tends to pill over time, especially after washing. Pilling is the process of fibers clumping into small “pills,” which reduce its insulating properties and make the garment look worn or shabby. Fleece generates a high amount of static electricity, attracting lint, pet hair, and dust. If it isn’t treated chemically, synthetic fleece can melt at surprisingly low temperatures, a potential problem if worn by someone sitting close to a campfire.

Fleece Jacket Features

Most fleece jackets have long sleeves, a short stand-up collar, full-length zippers, and some configuration of pockets. Hand-warmer pockets are standard on most jackets—if you’re going to wear your jacket with a climbing harness or hip-belt, make sure the hand-warmer pockets sit above the hips so they can be used even with gear on. Chest, bicep, and interior stash pockets give the wearer plenty of options for carrying electronics and personal items. Pullover fleeces with ¼- and ½-length zips save on zipper weight.

Moving into the more technical realm, underarm zips facilitate ventilation and temperature regulation, and occasionally appear on heavier-weight fleece jackets. Hoods that fit under a helmet or shell are popular with backcountry skiers and mountaineers. Packs’ shoulder harnesses tend to wear and pill fleece quickly—if you plan to wear your fleece ski touring or backpacking, look for a jacket with durable nylon or softshell patches at key wear points. Longer cuts and thumb loops keep layered pieces tucked in and in place.

Fleece Weights: 100-300, Grid Fleeces, “R”s

Fleece “weight” refers to the loft and thickness of the material used in a jacket’s construction, and two common scales exist for describing fleece weights. Most companies use the Polartec scale of 100, 200, 300—the higher the number, the higher the loft of the fleece, and the warmer (and heavier) the jacket will be. Fleece jackets with 100-weight ratings are lightweight, highly breathable, offer the wearer a wide range of movement, and work great as light layering pieces for aerobic activities or warmer conditions. Jackets with 200-weight ratings represent the middle ground in fleece, and this tends to be the most popular weight due to its versatility and ease of layering under hardshells. A 300-weight fleece is significantly loftier and heavier, more difficult to layer, and generally designed with cold or extreme weather conditions in mind.

Grid fleeces feature a grid pattern on the inside face of the jacket that facilitates air circulation and moisture wicking. Most grid fleeces have a smooth, bonded or woven outer face that resists pilling, increases wind-resistance, and makes for a versatile compromise between a traditional fleece jacket and a softshell.

Patagonia developed its own scale for describing fleece weights: R1 to R4. R1 to R3 roughly correspond to the 100 to 300 Polartec scale, whereas R4 is a hybrid fleece combining an R2 grid fleece with a Polartec Windbloc polyester.

Synthetics vs. Naturals

Fleece is spun from PET, which is made from stretched strands of plastic. That means fleece is made of oil, something that eco-friendly outdoor types have come to question over time. Like other plastics, though, PET can be made from recycled petroleum derivatives, and for fleeces, recycled PET poses no significant reduction in fleece’s desirable insulating and hydrophobic properties. Natural fibers like merino wool offer an even more sustainable option for midlayering materials. Merino wool, from Merino sheep, has soft, curly fibers with excellent insulating properties that don’t hold onto a wearer’s mountain funk, are renewable, and offer an alternative to suburban fashion trends.

The Takeaway

A fleece jacket is typically designed to function as a lightweight and breathable midlayer for outdoor activities in a range of weather conditions. Fleece jackets work best worn over a moisture-wicking baselayer material like polypropylene, Capilene, silk, or merino, and under a waterproof and/or windproof hardshell constructed with waterproof membranes or microporous coatings. But not all fleece jackets are created equal. Differences in synthetic and natural fibers, fleece weights, and jacket features make for a range of possibilities in choosing a fleece jacket. Though natural fibers like merino wool aren’t “true” synthetic fleeces, they can eliminate some of the key disadvantages of traditional fleece jackets, such as odor, pet-hair attraction, and non-renewable materials.


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