A Simple Outdoor Clothing System Layer 7: High Loft Insulation

Hi loft insulation is key to staying warm and happy in frigid weather. That, and a good dog.

If you’re going to spend time outside in the cold and snow you’ll want to add a compressible high loft jacket and pants to your clothing system.

This is the eighth in a series of articles outlining a simple clothing system for outdoor recreation. An overview of the system is offered here. Topics covered include baselayers, lightweight fleece insulation, midweight insulating jackets,  wind shells,  winter soft shells and rainwear.

The label that started it all. When did the Army start issuing puffy pants???

My whole deep dive into the idea of a simple outdoor clothing system started a thrift store. I was flipping through the hangers in a Goodwill in Green Bay, WI and looking for something interesting. My wife had found a pair of Pearl Izumi wind pants with three dollars in the pocket the year before at this store, and then a coat made from a Hudson Bay Company point blanket, so I had a pretty good feeling about my odds.

A couple minutes into browsing the men’s section I came across a pair of light grey, insulated pants with a Primaloft tag hanging off them. I looked at the label inside and saw that they were military issue and a size Medium/Regular. My size.

I did a quick Google on price, decided they were a good deal at 20 bucks, and took them home.

Then I tried to figure out what they were.

Staying Warm, Keeping Dry
Camping in winter conditions presents a number of challenges, ironically, one of the biggest is avoiding overheating. Skiing with a pack or hauling a tobaggan with snowshoes can be grueling work. It’s easy to heat up quickly and start to sweat. Once you sweat you start to put moisture into your clothing system that needs to be dried–usually by body heat. Add to this the fact that as soon as you stop for a break your body stops producing as much heat and you’ve got the potential for a real problem. If you sweat-up your clothes while you’re skinning uphill, and then stop for a break on a windy ridge, you’re likely to get seriously cold. Hypothermia cold.

The solution is to pack high loft insulation layers that are sized to fit over the top of your travel clothes. If you have a big, puffy coat and some insulated pants you can throw them on any time you take a break. This allows you to wear less insulation while travelling and reduces the chance you’ll overheat and sweat in the first place. Travel in clothes that keep you a little bit cool, suit up in the puffy stuff when you stop. Instead of getting sweaty, you stay dry, secure in the knowledge that when you do stop you can zip yourself into a mobile sleeping bag that will keep you toasty until you’re ready to start down the trail again. This is the idea behind high loft insulation.

Get Down
In the winter of 1992 the guys at Life Tools ran across a great deal on some down gear from The North Face. They were closing out a classic Sierra down parka and all the Nuptse down pants in the warehouse. Several of us snapped at the chance to outfit ourselves with this setup for the upcoming winter camping season.

The puffy Sierra Parka packed down small and could be pulled out during the day at rest stops to help preserve body heat. The pants didn’t get much use during the day, but shined at night standing around a campfire and sipping schnapps. Both could be worn inside my 5 degree down sleeping bag to help push the comfort range well below zero. It was an ideal setup.

Ideal, that is, until I discovered the Mountainshelter.

Hot Tents
Tucked in with the rental gear in the back room at Life Tools was a tent and folding wood stove combo from Mountainsmith called the Mountainshelter. We had a 4-man version with a small stove. Nobody used the thing. John and Craig had given it a try but pitching the floorless tipi tent and getting the stove to burn efficiently seemed too fussy to be practical. That all changed when Patrick Smith showed us how it was done.

Patrick is the founder of Mountainsmith and it turned out that he and my friend Brian had a mutual friend named Darryl. Brian and Darryl reached out to Patrick and suggested that we set up a dealer meet to show off Mountainsmith products to Midwest dealers on a winter camping trip in the UP (The Upper Peninsula of Michigan, yah). We called all the other regional outdoor stores and tried to get a bunch of people together for a weekend in the Porcupine Mountains.

In the end, we were the only ones who showed for the trip. So Patrick, Brian, Darryl and I piled into Brian’s rusted-out Toyota pickup and a borrowed Chevy van and headed North.

The Mountainshelter was out of production at this time, along with the high-end pulk sleds that Patrick had designed and sold in the earliest days of the company. But Patrick brought along at prototype 12-man Mountainshelter for us to use. The thing was like a circus tent. Two poles, two folding wood stoves, tons of room. We had a pretty luxurious weekend ski touring in the Porkies and Patrick showed us the ins and outs of how to run the stove and shelter.

John Manders kicking back in the Life Tools Mountainshelter. Gales of November Rendezvous, 1995.

After that weekend I was all-in on the Mountainshelter. I used the thing for every cold weather trip I could, even lashing the stove to the deck of my sea kayak for an October kayak rendezvous. In the Mountainshelter you could stay up late, lounging around in shirt sleeves instead of crawling into your sleeping bag at sunset and shivering until dawn. It was a complete winter camping game-changer.

One of the things the Mountainshelter changed was my need for down pants. With a fire stoked in the stove I didn’t have to bundle up, so my winter insulating layers were only necessary for daytime rest breaks. The down pants seemed unnecessary and made their way into a Rubbermaid bin at the back of my gear closet.

Meanwhile, back at the Goodwill
I never did get rid of those down pants. I held on to them, thinking that at some point they might come in handy for a cold weather trip. So when I picked up the Army surplus puffy pants at Goodwill, something clicked. I started to digging into what they were, starting with a Google search of what was listed on the government label: Trouser, Extreme Cold Weather. I dug a little deeper and finally came upon an article on a website called Imminent Threat Solutions that described the origin and development of the Protective Combat Uniform (PCU)–the clothing system that eventually became the current US Army Issue ECWCS Gen III. Whoop! Down the rabbit hole.

PCU Priorities
In this series of posts I’ve used the 7 layers of the PCU as a framework to simplify outdoor clothing choices. Too many choices leads to uncertainty about what will really work in a broad range of conditions. Narrowing things down deliberately is one way to insure that you’ll purchase clothing that is functional and avoid wasting money on gear you don’t need. If you can keep it simple you’ll spend less money and have a more versatile clothing system.

A fairly strict following of the PCU framework does a good job of setting clothing priorities for most outdoor outdoor activities, but when it comes to high loft insulation, it makes sense to cast a somewhat broader net. Within the context of the PCU/ECWCS system, synthetic insulation is a must in the high loft layers. For general outdoor use down offers some benefits. Both are worth a look.

Get Down! High loft down parka and pants. Mountain Hardwear Sub Zero SL Parka. The North Face Nuptse Pants.

Pros and Cons of Down
Quality down outperforms synthetic insulation in nearly every way. Down is lighter and more compressible than synthetics. It has a longer lifespan and maintains loft better over time than synthetics. What’s more, modern down from most manufacturers is treated to make it water resistant. This helps counteract the one BIG drawback of down–it loses loft and insulating power when wet, and is extremely slow to dry when soaked.

For years I discounted the problem of water resistance in down. All you had to do, I figured, was keep your down gear dry. Sleep in a good tent. Adjust layers so you don’t sweat too much. If you’re hot tent camping you’ll easily be able to dry any residual moisture that finds its way into your down clothes or sleeping bag with the wood stove. Water resistant down makes this even easier, as it is slower to absorb water and is faster to dry unless truly soaked. With all these advantages, it was hard for me to imagine why you would opt for heavier, bulkier synthetic insulation in clothing or sleeping bags.

My recent podcast dive has me reconsidering these ideas. Repeated exposure to moisture from perspiration, followed by compression in a stuff sack, can force water into down insulation, even water repellent down. Freezing conditions can then freeze the down plumes together, matting them and reducing loft. Over time, repeated cycles of damp, compression and freezing will reduce the warmth of down gear dramatically. Even water resistant down takes forever to dry if it is really soaked. If you are on an extended trip in cold weather a sleeping bag or clothing system that loses it’s loft can be dangerous. With a heated tent you have more of a margin of safety because you can dry your down gear by the fire. Cold tent camping requires a bit more caution.

The Real Advantage of Down
Despite the very real issue of moisture in clothing systems, there is one area where down truly outshines any synthetic competitors–ultra high loft clothing. Quite simply, down parkas and pants are available in much higher loft options than their synthetic counterparts. The most extreme examples of this are fully baffled parkas like the Marmot 8000 Meter Parka or Mountain Hardwear Absolute Zero Parka. These jackets are built like a sleeping bag with internal baffles that eliminate any possible cold spots. If you are heading into deep cold, or if you’re a person who gets cold easily, down offers you the warmest, lightest, highest loft jackets and pants available. These options are particularly useful if you’re travelling in very dry winter environments or are hot tent camping.

Understanding Down Fill Power
We can’t move on to a discussion of synthetic insulation before diving into one of the biggest misunderstandings that people have about down–fill power. The tags on down garments frequently reference the fill power used in their construction. Garments with higher fill power ratings are more expensive. Many people assume that they are also warmer than lower fill power options. This is not the case.

For instance, imagine you are comparing two down coats that look virtually identical. One coat is filled with 800 fill power down. The other is filled with 650 fill power down. Which one is warmer?


The coats will be equally warm. Fill power has little to do with warmth. LOFT is the key factor in how warm a down garment will be. It’s not the fill power that counts, its how puffy the jacket is. Puffier jackets are warmer. Thinner jackets are less warm.

If loft is the key to warmth, what does fill power signify? Fill power has to do with the quality of the down in the garment rather than it’s warmth. Down rated at 800 fill power has more volume per ounce than down rated at 650. This means that you get the same loft for less weight when you switch from 650 to 800 fill power. Higher fill power garments will be lighter. They’re also typically more compressible and longer lived since the higher fill power down is made from higher quality down plumes.

What this means is that, all other factors being equal, a coat stuffed with a higher fill power down will be lighter and more compressible than one filled with less expensive down. It will NOT be warmer. You only need to spring for the more expensive down fill if you are trying to hold the weight of your garments to the absolute minimum. Few people need to do this.

When things get serious, go synthetic. Not as puffy, way better in the wet. Black Diamond Stance Belay Parka. Army Surplus Primaloft pants.

Synthetic Insulation
As you might guess, the biggest advantage of synthetic insulation for winter camping is its moisture resistance. Down feathers flatten out and lose their loft when soaked. Synthetic fibers don’t have this problem. In fact, synthetic insulations are made from polyester fibers which are naturally hydrophobic or water repellent. The fibers do not absorb moisture. This means that when a synthetic garment does get wet, either from perspiration or environmental factors, the insulation fibers themselves do not absorb water. The shell may be soaked, there may be water within the insulating layers, but the fibers themselves will be no more wet than your polyester baselayer might be. Put another way, synthetic garments may get wet on the macro scale, but they don’t get wet at the micro scale. This fact dramatically reduces the time necessary to dry synthetic insulating garments and makes it possible to dry them with body heat rather than next to a wood stove.

Consider the following scenario. You’re on a late winter snowshoe trip in the Boundary Waters, carrying a pack and pulling a light pulk sled. As you make your way along the shoreline of a large lake you fail to notice an area of weak ice in your path and break through. Both legs go into thigh-deep water. Even though the water is shallow, the combination of pack, snowshoes and sled makes it tough to crawl back onto the ice. You need to work your way out of the pack and free your feet from the snowshoes one at a time before you can get out of the water. By the time you’re finished and back on firm terrain you’re soaked with ice water from the waist down and all the way up both arms. Air temperature is just below freezing.

Sometimes you get wet. A misstep at the north end of Angleworm Lake, BWCAW.

If you’re wearing the clothing system outlined in this series your next steps are simple and effective. First, wring the water out of your clothing to the best of your ability. You don’t need to take them off to do this. Next, put on a puffy high loft insulating layer over your wet clothes. See to your footwear. Change socks. Start walking.

Once you start moving, your body heat will begin to drive moisture out through the clothing system and away from your baselayer. Within about 30 minutes your synthetic baselayer should be dry and you’ll feel substantially warmer. An hour or so of hiking should drive most of the moisture out of your lightweight fleece layer and through your soft shell. At this point you’re probably warm enough to ditch your puffy layers and put them back into your pack.

What happens to those puffy layers next is the main reason why synthetic insulation is superior to down when things get serious. All the moisture that was driven out of your baselayer and lightweight fleece will have passed into your puffy layer. If that layer is down, a good amount of moisture will have been absorbed by the down plumes. The jacket and pants might not seem like they have lost much loft, but when you cram them into a stuffsack for the rest of the day, the down fibers will be compressed and will freeze together. Next time the puffy layer comes out of your pack it will be a clumpy mess. If you don’t have a good external heat source available you’ll have compromised insulation for the rest of your trip.

If your puffy layer is synthetic it will have absorbed much less moisture. Most of it will have passed through the system out into the environment. What moisture is still trapped in the jacket will have very little impact on its insulating value, even if it spends the next several hours crammed into a stuff sack. When things get serious, synthetic is what you want.

[Update: Another key benefit of synthetic high loft insulation is that you can wear these puffy layers inside your sleeping bag to push the temperature rating lower. Since you are carrying these layers anyway it makes sense to take advantage of them to reduce the weight and bulk of your winter bag. Synthetic puffy layers are less likely to lose loft than their down alternatives when worn as part of a sleep system. In a future post I’ll explore the idea of sleeping bags as the final layer in a clothing system and the benefits of synthetic sleeping bags in challenging conditions.]

Types of Synthetic Insulation
Twenty years ago we had two main options in synthetic insulation: Polarguard and Primaloft. Polarguard was a bulky continuous filament insulation with a reputation for durability. Primaloft was a shorter fiber insulation that had a softer hand and a more down-like feel. Both were very water resistant. Polarguard tended to be favored in sleeping bags because it had a bit more loft for similar weight and better durability when repeatedly stuffed and unstuffed. Primaloft frequently got the nod in clothing because it was more compressible and had a softer hand.

Today there are a bewildering variety of synthetic insulations on the market. Primaloft is still on the scene, but Polarguard has gone. Every manufacturer of sleeping bags and synthetic high loft clothing seems to have a proprietary insulation with a slick name. How the heck does a person make sense of all these different options?

In general, I think it is safe to say that continuous filament insulations like Polarguard are more durable and maintain their loft better than shorter stable, bonded fibers like Primaloft. That being said, I’ve been digging into the details of these various synthetic insulations trying to figure out which ones are short fiber and which are continuous filament and, frankly, I’m ready to give up. There isn’t a lot of transparency out there when you start digging.

The whole topic is fairly confusing and a little bit frustrating, so instead of focusing on the details of each insulation, I decided to come up with a simple rule that skips the need for a PhD in textiles engineering. It comes down to brand and brand.

Choosing Between Synthetic Insulations
When choosing synthetic insulation layers I focus either on a recognizable brand of insulation, or a reputable brand of clothing. Preferably both.

For instance, Primaloft Sport is an established, quality high loft insulation brand. That’s what’s in my Army surplus pants. After much testing, the US Army recently switched the spec for puffy layers from Primaloft to Climashield. Climashield is a continuous filament fiber similar to Polarguard that offers superior durability. Given the testing and field use that has gone into both of these insulations I think it is safe to consider them both to be safe choices, with Climashield getting the nod for long term durability.

But what about all the proprietary insulations from all the clothing manufacturers in the Outdoor market? What about HyperDAS, PlumaFill, Thermal R, Thermoball, Heetseeker, and on and on and on? Here it gets a little tougher, because, while many of these insulations offer impressive loft and compressibility, it’s hard to know how durable they will be over time. The problem of Thinsulate Lite Loft comes to mind.

Back in the 1990s 3M introduced a sleeping bag insulation called Thinsulate Lite Loft that seemed to outperform Polarguard in every way. It was lighter, more compressible and had a softer hand than Polarguard. Lite Loft performance came close to down, and well respected sleeping bag manufacturers like Moonstone and Sierra Designs jumped on board and switched their lines over entirely to the new material.

Problem was that Lite Loft didn’t hold up. It was puffy out of the gate but after a year or so of use it would go flat. There were a lot of useless synthetic bags out there a few years into the Lite Loft experiment, and a lot of folks who got burned.

So when it comes to proprietary insulations it can be hard to judge how well they will hold up over time. The best brands extensively test their insulations and back them up with a strong warranty. This is where the second “brand” comes into my heuristic. If the product is sold by a respected outdoor brand with a solid warranty there is a good chance the stuff will work. Should the insulation degrade prematurely you will at least have the option of pursuing a replacement under warranty. This isn’t a perfect solution, but absent third-party testing and evaluation of all the myriad products on the market, it may be the best we can do.

How Puffy?
How puffy should your puffy layers be? As puffy as you can find. I’ve tried a variety of lighter weight insulating jackets and for true winter use I prefer something with as much loft as possible. Down sweaters, Puffball Pullovers, Primaloft sweaters, short-waisted down jackets, Nano Puff hoodies–all of these jackets work OK in cool weather, but all of them come up short when you’re looking for a layer that will be truly warm in winter conditions.

I currently own two high loft jackets for winter travel. The first is a Mountain Hardwear Sub Zero SL Parka. This is a thigh-length, baffled down parka with a hood. It’s exceptionally warm and compresses down to almost nothing. Mountain Hardwear doesn’t make this jacket any longer but similar parkas are available from a range of manufacturers. A down parka like this is an excellent choice for deep cold weather trips, especially in conjunction with a hot tent.

My second parka is a Black Diamond Stance Belay Parka. It is a very puffy hooded synthetic parka that hits below the waist. It’s bulkier than the Sub Zero in a stuff sack and has less loft, so it won’t be as warm, but it is the puffiest synthetic parka I could find from a well regarded brand at an affordable price. I plan on using this parka for most of my future winter trips so that I have the added margin of safety that synthetic insulation provides.

I don’t think that any of the thinner synthetic puffy coats are really adequate for an outer insulation layer in true winter conditions. They are certainly nice to have in spring and fall, but they aren’t really necessary within the parameters of our simple clothing system. If you have all the other layers of the system in your closet there isn’t really any reason to add a thin puffy layer to your quiver. It won’t be warm enough for winter and it will be redundant with your midweight insulating jacket. Skip the thin puffy jackets.

Pants are a little easier than parkas because there aren’t quite as many options. There are only a few brands out there that make puffy pants at all, and most of these are not quite as lofty as my old down pants. Down pants are available from a variety of manufacturers but are typically quite expensive. Unless you’re planning to climb K2 it’s hard to justify a massively puffy pair of down pants. In fact, given how affordable they are, surplus puffy pants may be the best option out there.

Surplus Options
The ECWCS Level 7 Trouser and Parka are currently made from Climashield insulation and are a durable, affordable choice if you are leaning toward synthetic puffy layers. These garments come in a wide range of sizes and, in most cases, will cost less than half of what you’ll pay for similar garments from major outdoor brands. The pants in particular are very affordable. They even come in a a fairly neutral color. Surplus puffys don’t offer a warranty but given the established durability of Climashield they are a safe bet. Make sure to size down one full size in the parka if you go this route. The parkas are cut to be worn over body armor. Buy your normal size in pants, they are cut to fit over layers.

Inside pockets allow you to dry gloves and socks.

Parkas should have a hood, full front zipper, handwarmer pockets and internal pockets for drying gloves and socks. Your parka hem should hit below the waist to overlap with your puffy pants.

Pants should have full size zips to allow easy on and off without removing skis or snowshoes. Clip-on suspenders can be added to any puffy pants and are a big help in holding them up.

High loft insulating layers should be sized to fit over the top of the complete cold weather clothing system. This means the parka should fit over baselayer, lightweight fleece, midweight jacket, wind shell and soft shell. Pants should fit over baselayer, lightweight fleece and soft shell.

Full size zips on pants make it easy to get them on and off without removing skis or snowshoes.

Make sure to try on your layers with your puffys. For some reason there is currently a trend toward a slim cut in the sleeves of parkas. This is my only complaint about the Black Diamond parka that I purchased this year–the sleeves are a little tight when I have all my layers on underneath. I would prefer a little more room. Try them on first to make sure they fit.

Buy This Not This
Buy the puffiest high loft synthetic parka that you can find. Make sure it has a hood and fits over all your other layers. If you get cold easily and will be camping with a heated tent, buy a super high loft hooded down parka. Buy a pair of Army surplus ECWCS Level 7 pants.

Don’t buy a thin puffy jacket. Don’t buy a jacket without a hood. Don’t buy high loft down layers if you are taking extended trips in challenging conditions.

A Final Note on the Mountainshelter
Patrick Smith sold Mountainsmith some years ago and started a new outdoor brand called Kifaru. Kifaru immediately began to produce a new version of the Mountainshelter with a revised stove design. My friend Scott and I purchased one of these tents back in the early 2000s and have been using it ever since. Kifaru tents and stoves have evolved over time and are lighter and stronger than ever. If you are interested in checking out their lineup of tents and stoves you can find them here.

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