The term ‘softshell’ has been so abused over the years that it’s just about meaningless, with a Walmart denim Wrangler jacket being as ‘softshell’ as a North Face ‘softshell’, in that when things are good they’re great, but when things are anything but good, they’re terrible.
First off have you read my essay The Art of NOT Suffering? I’d say this is a foundation piece in understanding how and why you stay comfortable and alive in the mountains (hint, it’s not about wearing lots of clothes, in fact often it’s the opposite). Having a full grasp of what ‘comfort’ is, understanding how clothing works and its interaction with the body (fibres, sweat, loft, skin and core temperature), then slowly testing these ideas is vital, many of which are counter-intuitive (going by intuitive thinking is bollocks, ie experts told us to stay off the fat in order to stay thin, which made 160 million Americans obese!).
So first you need to understand your body, which it sounds like you do, i.e. you’re a sweaty bastard, which either means you’re super fit and have a very efficient body, or the opposite! As Dr gear I’d say you’re sweating because you’re wearing too many clothes in the misguided belief this will make you comfortable (it won’t).
Imagine a minus 10 day with little wind. On such a day you can go out and run in just tights and a thin long sleeve top, maybe even a vest and shorts. Throw in a little wind and maybe you’ll add a thin windproof made from unproofed nylon. Your hands and head and feet need a little more, so you add in some gloves or mitts, a hat and wool socks. As long as you’re moving you’re warm enough, and if you’re fit, you can adjust your pace to suit the required temperature you need. Even at a slow jog, your body is pumping out heat, and if you push it, it’ll push out sweat to cool itself, which with high heat or real cold condense into steam as it hits the air. If you can avoid sweating if you stop you will remain warm for a minute or two, even feel even hotter due to the air no longer sucking away the heat, but soon you’ll feel the cold sucking the heat out of you. If on the other hand you’ve got sweaty and your clothes are saturated you will chill immediately, if not before, the air sucking at you, cooling your skin and your core. Have you checked out that guy Wim Hof? A lot of the stuff he does is just about understanding his body, a naked man can be warming in sub-zero temperatures (in still air), then someone whose thick winter clothes are saturated.
All this above is the way you want to think about the ‘action suit’, clothing that will reduce sweating and overheating to a minimum, while protecting the user from snow, wind, rain etc. This is not an easy thing to do, but the colder it gets the easier it becomes. Below freezing is where a true softshell (Montane Extreme for example) really works as it’s designed to be a single layer, rather than multiple layers (again, one is intuitive, the other counter). The single layer is like an Inuit jacket made from caribou or seal skin (skin out, fur in, so windproof and warm), which when worn over the skin allows the hunter to just dump all their heat quickly, something that’s impossible to do with a traditional layered system. Now the problem comes when it’s raining, as you need a system that’s robust enough to keep you warm if it gets wet or damp, plus if it’s raining then maybe you do want to be walking around in a caribou coat! Here you need a layer next to your skin that can cope with moisture without getting you too hot and making things worse (because in any shell layer, be it Gore, plastic or newspaper, you will get wet if you’re doing anything but bird watching).
Some fabrics are good when wet, such as wool, but only when you’re moving, but are slow to dry (if your skin temperature is low it will not dry). Others, such as man-made fabrics, do not retain much water, and dry faster, but are not that warm when wet (again, if something is not warm it will be slow to dry). The construction and micro-loft of base fabric are what’s important and ideally, you need a base that:
a: Does not absorb water (ie: cotton is bad)
b: Has a high enough micro-loft that it contains a good level of air per square inch, i.e. not super dense (old school Helly Hansen was just such a fabric).
c: Has minimum contact with the skin, a good example being a brushed polyester fabric or micropile. This means that even when a fabric is saturated it will feel dry, as the actual contacts points quickly dried (and dry skin will dry the fabric).
d: Allow the sweat out. Some companies use a mesh fabric (such as the current Marmot DriClime), to create a fabric with more pathways out for sweat, plus pockets of air do not get wet but do hold dead air). With this style, you can dump heat very effectively.
So what are the stand out base layers, or if not standout then better than cotton? Well on the conventional front I worked with Montane for several years and found their Premino base layers hit a lot of marks for me (being a mix of Merino wool and Primaloft, Patagonia’s Capilene air being very similar), as the light to medium weight tops had a low density and was a good balance between a natural and a synthetic (it didn’t stink but dried fast). I remember going paddle boarding once with my kids at Convict lake near Mammoth. I had a premino top on while the kids had cotton t-shirts, and of course, we all fell in. Paddling back I realised why they were shivering hard after twenty minutes, my top ‘felt’ dry, which I doubt would be the case if it had been 100% merino (wool after loses its shape when wet, which undermines the materials skin contact area). My ideal base layer would be full sleeve but have sleeves I could roll up, a feature a long front zipper (down to your belly button, so you could dump heat), a hood (heat retention is as important as heat dumping), and a long, not too thin and not too thick, and have used this kind of top in some very cold temps when active.
But by far the best - and in some ways worse - base layer out there is the Norwegian brand Brynje, which is just made from Polypropylene mesh, and is about the most unsophisticated underwear you’ll find. Why it works so well is Polypropylene will not absorb any moisture and being mesh is primarily air, so is warm when the air is still (under a windproof for example). It dries super fast and has the lowest ‘chill’ factor of any fabric I’ve used (whenever I climb a wall my ‘storm kit’ always includes a Brynje top and bottoms as insurance).
I’m waffling I know, but these things are the foundation of your clothing system (action suit). Get it wrong and everything will suck. What’s more, this layer is the cheapest layer of all your clothing, and with the right base layers (and knowing how to use it), you can wear almost anything over the top.
To finish off the action suit you need to add a windproof or waterproof layer, with windproof being best if possible. This could be something light, such as Pertex/nylon, or close-knit stretch fabric, which will be tougher, the classic example being the classic guide pant. These two layers (say base layer, windproof top, guide pants) will actually serve someone well when active over a surprising range of temps. Of course here you need to begin adding in and taking away items when it gets cold, your pace is slower (say climbing vs walking in vs belaying), say a light synthetic duvet, light fleece, gilet etc. Of course, here you’re moving back into a trad layered system, which isn’t a problem if you get the fundamentals as you know how to use these layers right, taking them off and putting them on before you get too hot or before you get too cold. The best example of this would be skiing in Antarctica, where you’d imagine you’d be wearing a down suit in temperatures down to minus thirty, yet in reality, you’re only wearing base layers and shell (but with thick mitts, super warm boots etc) Here you also throw your static belay jacket layer, which can be thrown over everything (again this way you remove all that insulation the moment you take it off before moving).
For sub-zero temperatures, when you’re moving slow, this is where the real softshell works best (fibre pile with a windproof shell, or something like Patagonia Nano Air), as it wicks really well, can dump heat, yet has very good insulation, and does not require a hard shell over the top (a hard shell can be over the top in many sub-zero situations). Yes, these layers - such as the Extreme - can appear very heavy, but in these temps, they can replace all other layers, so overall they can prove lighter. I’ve not used the Helium Extreme myself, but it was designed to try and bridge the gap between a heavyweight ‘shit gets serious layer and something more adaptable (more like the Patagonia Nano Air does).
So I guess my advice would be to nail the concept and efficient use of the clothing you have (‘soft shell’ is really a way of using clothing rather than the clothing itself), and maybe look at picking up a Brynje top. But most of all try and look beyond the marketing bullshit and understand the limits of real-world outdoor comfort, and see the small amount of suffering as all part of the type two fun!