I think of it as "The 'L' Word," because when people hear "Layering," they tend to zone out. It's a term that carries with it an almost dismissive familiarity, but even avid outdoor enthusiasts frequently have an incomplete understanding of the concept. It isn't really about staying warm. It's about staying cool. It's about temperature regulation.

Layering is about keeping your cool, NOT about getting you warm.

The easiest way to be warm is to grab the biggest, poofiest hooded down parka you can find. If you're doing much more than belaying an ice climber or standing at a bus stop, though, it's easy to overheat... and although being too warm might sound great, your body doesn't see it that way. The "You" of your heart and mind might cherish excess warmth, but your body has one mission: Keep it neutral. If you're too hot, your body will work to cool you down.

It might strike you as cruel, but it is eminently usual. If we give this particular rabbit hole more consideration, it's quickly apparent that your situation can only snowball until you're totally jammed. To wit, you're overheating so your body starts cooling you down... so you bundle up more, and your body redoubles its efforts to cool you... so you put on an extra hat and do some jumping jacks, and your body works even harder to cool you... all in all, it's not a scenario that ends in comfort, which is why I stress the importance of staying on the cool side of comfort.

Be proactive in removing layers... Take them off before you're too hot. There's a sensory sweet spot in that area between feeling cold and feeling that you'll be warm soon; when you sense you've started warming, or that you're not cold, it's probably time to shed a layer. The more aerobic your activity level, the more proactive you need to be in removing layers. You don't need to wear much when your metabolism is cranked to high!

Imagine that you're in your house and the thermostat is on whatever "regular" is for you, maybe 68*F. You're comfortable, maybe wearing a long-sleeved shirt or even a flannel. Now imagine that the thermostat's set at 80 and the furnace is humming along... if you're like me, you won't be wearing much more than underwear. Or maybe you visit someone who you know habitually has their heat set high, so you wear a bit less clothing there than you would at home. Just as these indoor situations are a microclimate of sorts, your body maintains its own microclimate.

Your body doesn't really care what the weather is like outside. Or inside, for that matter. Your body just wants to be the same temperature, all the time.

By way of example, I've had a sedentary day. I was wearing a very thin merino wool henley and an unbuttoned flannel at the desk; my dog started bringing me bits and pieces of laundry, which means he's bored and it's time to go for a walk. I keep the house around 65F, and it's a bit below freezing outside, around 28F. I tossed on a fleece vest (okay, wool, but same idea), an uninsulated rain jacket, and a hat on our way outdoors. I wore a pair of leather work gloves that were stashed in the jacket pocket and we walked about a mile. When we got home I removed all but the thin merino shirt, since the walk had boosted my metabolic heat production & I was too warm in the flannel. The point is that I didn't need to add much of anything to go outside, because I knew that the activity would turn on my "furnace."

If I had gone out to sit on a log for a few hours instead of walking, I would've needed to dress differently. Adding layers does add insulation, but if you're headed out to hunt from a tree stand, for example, wearing enough layers to stay warm can restrict your mobility. For sedentary activity you're probably better served by just throwing on one or two big thick layers...

I know, sometimes it's hard to feel motivated about going out into the cold. Sometimes we don't care if wearing a really warm jacket will make us too warm... if we're going outside, darnit, we're gonna be warm. When it's bitter cold and I'm headed out snowshoeing, and I want to make sure I'm warm enough, I'll toss on a sort of "ceremonial" down jacket or something. I know I won't be able to wear it long. But it gets me out the door feeling cozy, and after moving 5 or 10 minutes I shuck the jacket and stash it. Actually, for single-digit snowshoeing my "go-to" combo is a wool baselayer, a super light windbreaker, a down vest, and a hat. The down vest never stays on long, but it's sure nice to have!

There's a lot more we could discuss, but I wanted to get this idea out there for you as winter comes on. I've met countless people who have approached "layering" as "wearing a bunch of layers to stay super warm," and thought this angle of the concept might be of help.

Down fill power is one of the most broadly misunderstood concepts in the outdoor industry, even by those who sell down-filled products. Through my work in specialty retail I overheard countless misguided explanations of fill power from people impressing companions with their knowledge, retail staffers, and a whole stack of others who should've known better. I think that what happens is people try to "run" with an incomplete understanding, and fill in their gaps of knowledge with supposition. Let's take a nuts n' bolts look at fill power.

The fill power numbers are those that you'll frequently see on a hang tag or even embroidered onto a product, usually a number ranging from 500 to 900. Maybe you'll see a "625" or a "900+" or a "750..." but really, why do any of them matter? What do they mean? It's super simple, but also super critical to understand this core concept... in fact, it's so important I'll set it apart:

The fill power number represents how much space one massed ounce of that down occupies.

By extension, the weight of one ounce (as weighed on a scale) of 550-fill down will occupy 550 cubic inches. One ounce of 900-fill down will occupy 900 cubic inches.

The significance, the difference between those fill powers, relates to that old proverbial question about a glass half-full... Given the same weighted amounts, 500-fill down won't fill as much space as 900-fill down. In fact, an ounce of 900-fill down fills nearly twice as much space as 500-fill down. But that doesn't mean that 900-fill is better! That's so important I'll say it again:

900-fill down is NOT BETTER than 500-fill down.

It IS different, and it CAN be better for SOME situations... but sometimes 900-fill down is a WORSE choice than 500-fill down. Similarly, 900-fill down is NOT WARMER than 500-fill down... but this is where things can get confusing for people.

If you have equal weights of two down samples, the 900-fill sample will fill nearly twice as much space. Given that the purpose of insulation is to create dead air space, the 900-fill sample will create a lot more dead air space. An ounce of 900-fill down is warmer than an ounce of 500-fill down, BUT IN PRACTICAL TERMS other variables will almost always be more significant in understanding how warm something will be.

I say this because each fill power rating has its own sort of specialized niche. An automotive analogy: A 3/4-ton pickup can't accelerate or handle like a Corvette, and the Corvette can't haul a load of lumber.

The reality is that 900-fill down won't be used in applications better-suited to 500-fill down, or vice versa. The advantage of higher fill powers is that you can use less of them to achieve the same amount of warmth of lower fill powers... Higher fill powers allow you to use less weight and less bulk to achieve the same amount of warmth. This DOES NOT MEAN that a 1/2"-thick 900-fill jacket will be as warm or warmer than a 2"-thick 500 fill jacket. The amount of loft, the poofiness, is what determines warmth. It's the thickness of the jacket, not the fill power of the down, that ultimately determines how warm the jacket will be.

It is the THICKNESS of the jacket, not the fill power of the down, that determines how warm a jacket will be.

If I made two jackets as examples (maybe this is something we can do for a future video?) and filled both of them to 1-inch thick, using 500-fill down in one jacket and 900-fill down in the other jacket, they would be equally warm. Re-read that part! EQUALLY WARM! The difference would be that the 900-fill jacket would use less down to get that thickness, so it would be lighter weight and would pack smaller.

And that, friends, is the reason to use higher fill powers... you can create lighter weight things that stuff into smaller balls. It wouldn't make a lot of sense to use 850 fill inside a nylon shell that could be made with a lighter-weight nylon.

Lower fill powers, frankly, are better for routine use. The products made with lower fill powers will cost less... both because the down itself is less expensive, and because the materials enclosing it are also less expensive. Lower cost aside, the lower fill powers are also more versatile, more resilient. They don't require as much fussing or attention. Here at Backcountry Bonsai we ran some experiments on the effects of humidity on down, and found that the lower fill powers retained their loft better than higher fill powers under humid conditions. Anecdotal experience also indicates that higher fill powers are more susceptible to losing loft and/or matting under more extreme or prolonged conditions.

Heavier shell material will actually compress higher fill-power down, whereas it will not have the same effect on lower fill powers... We believe that, by extension, and in consideration of our humidity testing, lower fill power downs are overall more durable. (Gross comparison, what's easier to break... one toothpick, or ten of them in a bundle?) So a lower fill power product can cost less, work better under worse conditions, and last longer... the trade-off being that it does so at the expense of some additional weight and bulk.

You will also see down billed as "grey" or "white," and you should know that color has NO effect on insulating properties. In our experience working with material that weighs less than an ounce per square yard, we prefer grey down simply because it is less "contrasty" behind the rich fabric colors we prefer. (White down is more visible through the material, and the whiteness somewhat "fades" the material color.) Hey, pop quiz: What weighs more: A ton of feathers, or a ton of bricks?

I hope you said they weigh the same! In a similar way, 700-fill down is 700-fill down... regardless of whether that down was sourced from duck or goose. "Goose down" has a certain cachet, I'm guessing because of some historical basis, but if all other factors are equal, duck and goose down of the same fill power are of the same quality, same warmth, same weight, and same compressibility. True eider down, the undisputed king of all downs and easily costing 10 times more than "standard" 900-fill downs, is duck down.

One last thing we should address: all of the downs we're talking about are hypoallergenic. Do you have allergies? Horrid allergies? Cool. You'll be fine with down. What people are allergic to isn't down itself, but the dust and dander and extraneous oils & dirts associated with FEATHERS. Feathers, by the way, are not down. Feathers have quills... you know, like those super-old-school feather pens in the ink well. Feathers poke. Feathers can wreak havoc on allergies. A lot of upholstery and even home bedding is filled with feathers... they're tougher, they "give way" less, so they maintain more cushion. (If you had a pillow filled only with 900-fill down, when you laid your head down there wouldn't be anything left but two layers of nylon between your head and the mattress.) I had a featherbed for a short while... could NOT sleep on it, because of all the allergens associated with feather products. When you start talking about down, though, from fill powers 500 and up... you're not talking about feathers anymore. The down we're talking about, even the 500-ish stuff, is pretty high end. You're gonna love it.

Musings