Polartec Alpha was designed to be a batting insulation, encapsulated between two shells. Alpha Direct was designed as an inner lining, to be sewn to an outer shell. The cottage industry was smart to build these as stand alone garments because that allowed it to be used as a modular system. Instead of being stuck with the shell that the Alpha Direct was sewn to, you could mix and match depending on the conditions. You could use the mechanical ventilation on those outer shells to cool down because the Alpha has little resistance to air flow when exposed. Of course, in situations where one needed to dump heat, or they only needed light insulation, they could even remove the outer shell and use the bare Alpha. With a three layer system of Alpha, breathable wind shell, and rain shell, we are able to cover a huge range of conditions. The ultralight community has taken this even further and is often pushing to omit the wind shell.
So how should you use your Alpha? Well, the answer is really to use it however works for you….but get the details right first. I have caught myself saying “Alpha is useless without a shell”, which is of course hyperbole. Bare Alpha with no shell does have some utility. It’s just that it’s such a small fraction of its utility without a shell. On the flip side, there are some who claim Alpha is just as functional without a shell, as with. This is certainly incorrect. This is served by confirmation bias in an attempt to justify a two layer system with just an Alpha layer and a rain layer. This system, by omitting the wind shell, takes this wide and adjustable comfort range, and narrows it down to a couple small slivers of that spectrum. Now, that is ok if your use case exists within those slivers….or you just really want that to be the way. Our bodies and systems are adaptable and if we really want a method to work, we can adapt and make it work. People will claim to have hiked thousands of miles in their bare Alpha and therefore call it an optimized system. People have also hiked thousands of miles sleeping in a mylar emergency bivy. Does that mean it’s the best system for everyone? No. It means that they adapted and made a less than ideal system work so they could carry a 3lb base weight. Same with the Alpha systems. Bare Alpha will have some utility, but it will be a small fraction of its potential warmth, even in still air. In windy conditions and when the body is in motion, this fraction gets progressively smaller. Not to mention the snag durability of Alpha Direct is a joke. It’s abrasion resistance is not much better.
So if you are always hiking on buffed out high travel trails with no potential for snags…..and you really don’t need a ton of insulation, then this small sliver of comfort range could work just fine. The reality is that out on the trail, (even the buffed out ones) we experience temperature swings and changes in conditions that would push a bare Alpha user into a less than ideal comfort zone. As previously mentioned, some ultralighters might consider this an acceptable trade-off….to suffer a little bit to make that system work. In such a case, the two piece system user would then put on the rain layer to get the warmth they need out of Alpha. This takes the performance of the system from the 1000+ cfm air permeability of bare Alpha and chops it down to zero cfm (or close to it) of the rain shell and now we’re needing to manage overheating and moisture build up. It’s a very on / off type of system that can work, but is far from optimized for varied conditions.
If this sacrifice was being made to make significant reductions in base weight, I would be the first to board the train. However, this is all to drop a 3 – 4oz wind shell that can functionally fill in this massive range of comfort for me. I use an Alpha-based three piece system, pretty much on a daily basis for running, hiking, biking, and even casual use. With the Alpha, wind shell, and rain shell, I have the full range of options. The amount of time that the conditions call for bare Alpha is likely much less than 10%. The amount of time the rain layer gets used is only when there is heavy precipitation, which is also likely under 10%. The other 80% of the time it’s Alpha with a 100cfm wind shell over it….the way it was designed to be used. When I have reduced this to a two piece system, for most of that 80% time, I’m either too cold or too warm.
It should be noted that most of this applies to 60 gsm and 90 gsm Alpha Direct. At the 120 gsm level things start to look a little different as the length of fiber starts to cover over the open mesh, making it a more useful stand alone piece.