Editor’s note: If you’re new to our “From the Skin Out” series, be sure to check out Base Layers – Part 1.
If your base layers are a second skin for outdoor adventures, then mid layers are your microclimate and powerhouse manager. Often times this is the most neglected part of a good apparel layering system. Sometimes there’s good reasoning behind that; in hot temperatures you likely don’t need anything between your base and outer shell. Going into winter however, you shouldn’t get stuck with simply an insulated shell over your base layers, as you won’t be able to thermoregulate in multiple situations.
With that in mind, what exactly should you be looking for? A good mid layer for an adventurer on the trail will pick up the moisture wicking chain from your base without skipping a beat. For extreme cold applications, insulation is king. You’ll need something that provides high loft and a good warmth to weight ratio. Finally, for those of us on a budget (and let’s be honest, that’s all of us), there is the elusive insulating piece that can do both. If you’re looking for something that can wick like a soft fleece and keep you warm like down, some of the newer synthetic materials and blends are just what you’re looking for.
Your environment will be the biggest determining factor when picking a mid layer. Your first thought should be to the old adage, “Function over Form”. Identify your needs and search for the insulation material that best fits your purpose, then find an apparel piece that fits your application and body. Also be cognizant that every material comes with trade offs. If you’re picking something for sitting in a tree stand, loft and warmth will trump breathability. Likewise, for backpackers and hikers, you’ll want a more efficient material for dumping excess heat.
Like base layers, mid layers come in a lot of different flavors. Not only do we have to gauge different insulation materials like down, wool, and synthetics, but many puffy jackets also use technical liners and face fabrics with different properties. We don’t have the time to launch into a lecture on every product on the market, so we’ll touch on current market trends and some of the best standards that many manufacturers build to.
You’ve probably got a few pieces of technical fleece in your closet. Typically a loose weave of synthetic polyester fibers, most fleece straddles the line between warmth and breathability. Polartec is one of the largest fleece fabric suppliers, and their line ranges from ultra light weight like Power Grid (which is more suited as a base layer), to heavier, more tightly woven offerings like Wind Pro. For layering, fleece is an excellent option for warmer temperatures or high aerobic output when you may value breathability over warmth, although with thicker fabric you won’t have to sacrifice much of either.
Down is the gold standard in warmth. Due to its lofty characteristics, goose down has the highest warmth to weight ratio of any apparel insulation. However, unless your down has been hydrophobically treated like DownTek, it won’t provide much of anything when wet. This necessitates strong liner fabrics that can both be treated with a DWR, and provide a barrier for escaping feathers. When looking at a down product, it is important to understand the way the industry rates it. Every puffy coat and sleeping bag will have a “fill power” rating, which is essentially a fluffiness measurement. The higher the number, the more loft each individual feather has. So and 800-fill jacket will have less down per volume than a 600-fill jacket; this provides more space for warm air to be trapped. The trade off is cost. There is only so much down produced a year, so you’ll be paying a premium for that insanely light mountaineering belay jacket or -20 degree sleeping bag.
A couple of decades ago, fabric manufacturers started to mimic down with synthetic fibers. The goal was to build an insulation that could loft like down, maintain warmth when wet, and stay packable. Brands like Primaloft have largely achieved this by using polyester microfiber in very loose weaves. Early versions were developed for the US Military, and Primaloft still maintains a completely made in the US line for brands that need Berry Compliant supply chains. More recently, Polartec Alpha has pushed standards in breathability and compressibility even further, giving manufacturers what may be the very first “down killer” in terms of performance.
Summer: Arc’teryx Arenite Hoody ($169)
We like the Arenite because it doesn’t behave like a traditional fleece. The hard face to the fabric provides extra wind resistance, but the inside is incredibly soft. This has been our go to piece for summer camping and fall fly fishing. It is very abrasion resistant when compared with similar items. A very athletic fit is something you should be aware of as well. I am 5’10” and the medium fit perfectly. Pro tip: when packing it for a hike, fold it in thirds and then roll it from bottom to top. It will fit nicely in its own hood to save space.
Fall: Black Diamond Hot Forge Hybrid Hoody ($249)
Black Diamond’s Hot Forge line are light weight insulation titans. This season’s Hybrid version uses Primaloft’s Gold Down Blend in the body to preserve core warmth, and more water-resistant Gold (without the down) in the hood, shoulders and arms. Additionally, the jacket packs into its own internal pocket, so you’ll never have to go without having an emergency back up whether it’s on your winter morning commute or a long day in the backcountry. What’s more, BD used a Pertex Quantum face fabric that has an excellent DWR treatment so you can easily forego a shell in light rain or snow to preserve a little extra breathability on the move.
Winter: Eddie Bauer IgniteLite Flux 60 ($187)
Designed in conjunction with Eddie Bauer’s First Ascent guide team, the all new IgniteLite sets a high standard for cold weather performance. Breathable 60g Primaloft Silver insulation is sandwiched between a soft lining and a stretch woven face fabric so the IgniteLite will move with you. It features Eddie Bauer’s Storm Repel treatment – tested on multiple outings on the slopes of Mt. Rainier – that will keep you dry long after your friends’ jackets soak through. This is the mid layer we’ll be rocking for much of the ski season.