The Art of Insulation

Insulators and Mid Layers

Picture, if you will, a barren landscape. Drift snow traversing across wind-scoured tundra - a carpet of white in every direction. The temperature in these parts reaches as low as minus 50-degrees centigrade.

Across the horizon scuttles an Arctic Hare, happy as Larry in pursuit of moss and lichen to chow-down upon. The sprightly wee chap calls this environment “home” - you and I, we call it inhospitable. But what, you may ask, makes the Hare better equipped to survive in such extreme temperatures versus you or I?

Well, because Mr. Hare sports a coat of thick fur, shielding him from the elements by trapping, then warming, cold air between its strands - creating a cosy buffer between himself and the unrelenting cold - whilst we remain nothing more than (comparatively) hairless bags of skin, bones, blood, guts and blubber.

“But I want to be as snuggly and cute as Horatio Hare too!” you protest! Lucky for you we’ve got just the solution for your temperature-woes. The latter however… you’re on your own, you gremlin.

Don’t get left out in the cold.

Here at Freeze, we take warmth seriously. We believe insulation - specifically mid-layer - ranks as one of the most important pieces of kit you can take with you into the mountains and beyond. The correct insulator can be the difference between staying warm and mobile for long periods, versus the onset of hypothermia and (in extreme circumstances) death.

We really do believe everyone should own a least one insulator, and it’s because of this we pride ourselves on stocking the best range of mid-layers from brands such as Patagonia, Arc’teryx, The North Face, Fjallraven, Haglofs and Mountain Hardware - to name just a few.

The great thing about insulators is their versatility. Yes, they’re ideal for use on the slopes, in the backcountry and on Spring tours, but it’s far from unusual to see folk sporting them out on the high-street or at the beach when walking the dog - from early Autumn right the way through to Spring, they’re the perfect piece of layering to grab as you’re rushing out the door.

Choosing Insulators and Mid Layers

The Science.

Okay, so most people generally understand how layering works, but in case you were out the back of the bike sheds smoking fags at the time, here’s a brief explanation…

The general rule of thumb is that multiple, lighter layers are far more effective at keeping you warm and dry than a single bulky layer, that’s why we always advise layering a good shell jacket on top of an insulator, on top of a base-layer.

Base-layer is worn next to skin and its primary function is to wick moisture away from your body. Most base-layers will tend be either synthetic, wool (generally merino) or a hybrid blend of both. Cotton is a big no-no, the reason for this is that it’s a poor transporter of moisture and will saturate quickly, leading to rapid heat loss, known as “hyper-cooling.”

Your mid-layer has the job of retaining heat (hence “insulator”) and, as we’ve already established, the focal point of this opinion piece. They vary wildly in price, function and efficiency - all points we’ll attempt to cover in more depth as you read on.

Finally, you’ve got your outer-layer. Almost always waterproof and breathable (to varying degrees depending on the fabric) their purpose is to shield you from rain, sleet, snow and wind. We always recommend a shell jacket over an insulated one - Why? Because if you overheat in an insulated jacket you’ve generally got no option but to take it off. That’s simply not practical if you’re in the back of beyond and the weather’s closing in. Opting for a mid-layer worn under a shell means you can remove your insulator without also losing the weather-beating properties of the outer-layer.

Pretty straight forward, right?

Where to start…

Fleece, synthetic or down? There’s so many options available that it really can be difficult to work out what’s right for your needs. So, let us break it down for you…

Fleece is the cheapest of the three, but tends to get a bit of a tough time because your dad wore it religiously throughout most of the early-to-mid-nineties when it was, frankly, pretty shitty.

However, times have changed and with it, as has the quality of fleece materials. You just need to look at offerings like the Patagonia R1 Fleece - which uses Polartec’s Power Grid fleece to wick moisture while trapping warm air - or the Haglofs Astro II Zip Top - made of more “traditional” Pontetorto Micro-Fleece - to see that fleece has really upped its game in the last 20 years.

As an affordable and accessible introduction to mid-layer insulation, fleece delivers plenty of bang for your buck. Because fleece is usually single layer, it tends to be more breathable than a double-wall insulated alternative, which assists moisture transportation. However, the down-side to this is that heat is lost at a much faster rate than fill-insulated alternatives. Because of this, fleece tends to be best suited to resort riding, providing extra warmth on long chairlifts, or when sipping a beer at a mountain restaurant in the midday sun.

If you’re heading further afield, we’d suggest taking a fleece in your backpack as a “swap-out” layer. That way, if you’re overheating in your down or synthetic-fill layer, you can throw on your fleece and stow the other in you pack until you need a heat-boost.

Patagonia Insulators

Born from chemistry to keep you toasty warm…

Synthetic insulation bridges the gap between fleece and down. Manufactured using polyester strands which mimic the loft and insulating properties of down, synthetic fills offer a more affordable and ethical alternative to their counterpart, but are more carbon-intensive to manufacturer.

One of the many advantages of synthetic fills is their ability to stay warm when wet. This makes them particularly good when touring or hiking in slushy spring conditions, or in snow flurries and light rain showers. They also tend to be significantly lower profile and sleeker fitting than their down alternatives, meaning they fit more comfortably under a shell and don’t have too much impact in your range of movement.

Compared to down, the face fabric for synthetic fills doesn’t need to be quite as tightly woven to retain the fill within the baffles. In recent years, several companies have developed their own “coarser” fill fibres which has allowed them to use more open-weave, air permeable face fabrics. The most notable examples of this are the super-breathable Arc’teryx Proton and Patagonia Nano Air insulators - boasting a CFM rating (the measure of air permeability) of 35 and 40. In laymen’s / laywomen’s terms, a CFM rating of Zero is absolutely windproof (think GORE TEX Windstopper) while by contrast, the average cotton t-shirt has a CFM rating of between 25 & 30 - the higher the CFM, the more breathable to fabric.

On the whole, synthetic fibre fills are a solid choice in terms of warmth, bulk and breathability. They’re generally a great balance of all three and for the most part will service even the most adventurous riders well. However, if you’re in need of absolutely bomber-warmth, down fill’s your one-way ticket to warmth Nirvana.

When it comes to staying warm, Mother Nature has humankind trumped…

Down can occasionally be a bit of a technical and ethical minefield to navigate.

First and foremost, there’s the concern over animal welfare - down is primarily sourced from geese and ducks - and it’s a concern which we here at Freeze share. It’s no secret that there’s been some abhorrent practices undertaken in the name of down production, the most well-reported being “live plucking.” Freeze doesn’t condone this method of down-production, which is why we look for RDS certified down in all down products we stock.

Why use it at all in that case? Well, down is the most efficient insulation available - it’s far warmer per weight that any other form of insulation and it’s long lasting. It’s also far better for the environment than synthetic insulation and fleece - it’s natural, it’s biodegradable, it conserves resources by utilising by-products of food production and it’s renewable - on the whole, down products create a much smaller carbon footprint than synthetics.

Down insulators come in all shapes and sizes, from the super-lightweight Mountain Hardware Ghost Whisperer, to the standalone ultra-burly Arc’teryx Ceres SV - the latter of which is perfect for overnight stops in mountain refuges or bothies – but what they all have in common is their fill power.

What’s fill power, you ask? In the simplest terms possible, “fill power” is a measure of loft, or fluffiness, of the down. The higher the loft, the more the feather “bulks up” when left to stand, which in turn means the more room in which to trap air – more trapped air equates to a higher level of insulation, therefore the higher the fill power, the more insulating the mid-layer will be.

Fill power is expressed in cubic inches per ounce (in ³/oz) - a lofting power of 400 - 450 is considered medium quality, 500 - 550 is considered good, 550 - 750 is considered very good, and 750+ is considered excellent.

A pitfall of down is that it’s very poor at insulating when wet, however as their main area of use is intended to be cold, dry climates this is rarely an issue. Another concern is often their sheer bulk when fully lofted. While this can be an issue with some of the belay-style down jackets, there’s plenty of low-profile options which won’t pose any issue when worn under a shell – examples or which are the Arc’teryx Cerium LT, the Patagonia Down Shirt, or the aforementioned Mountain Hardware Ghost Whisperer.

Fjallraven Insulators

The snugly-warm conclusion…

As Autumn rolls in and the mercury starts to drop, there’s a strange sort of comfort that comes with pulling on an insulator. Perhaps it’s a signal to sub-conscious that Winter’s just around the corner and it won’t be long until our next hikes into the backcountry. Maybe it’s a reminder that we’re vulnerable to the cold, but through the power of human ingenuity, we can learn to adapt and thrive in it. Whatever the reason, there’s something all-encompassing about putting on an insulating layer - it’s what we imagine getting a hug from a Yeti would be like.

The truth is, we can’t tell you which of the three variants is best for you and your needs - each has its pros and cons - but hopefully you feel a wee bit more informed on what each of those are after reading this and you’re now armed with the knowledge to keep Jack Frost at bay this Winter.

Shop all insulators.