The Great Outdoors Stack Exchange is a question and answer site for people who love being outdoors enjoying nature and wilderness, and learning about the required skills and equipment. It only takes a minute to sign up.
Sign up to join this community
This question asks why we don't apply the layer principle on trousers. Personally, I disagree with the pretext of the question: I certainly do apply the layer principle on trousers when cycling in cold (-10°C < T < -40°C) weather, and I think skiers do, too. The answers to this question on sleeping bags also show a certain degree of discussion.
Assuming dry clothes, is there any situation where the layer principle does not apply?
It's not clear what you think the layer principle, is but you don't have to dress in layers. It's the performance of the complete stackup that matters. In cold weather, this could be achieved, for example, by a polypro sweater then wool sweater then wind breaker, or with a single "winter" jacket. Both can be made to keep you warm equally well, and the winter jacket could even have roughly the same kind of layers all in one unit.
When you're just walking around town and going beween the car and a store, the single thick jacket can be fine. When hiking, layering has distinct advantages. It's a lot more important when hiking to tune your clothing more tightly to the weather and your activity than around town. Too much and you get sweaty. Too little and you get cold. Also, the amount of insulation you need will vary significantly depending on whether you are exerting yourself like when hiking up a hill, or just sitting around eating lunch.
Layers allow you to tune what you wear to the conditions for the least amount of weight and volume of stuff. You can adjust just 3 or 4 possible layers to be the equivalent of a wide range of single-purpose garments. That pile of single-purpose garments would much bulkier and heavier than the 3 or 4 layers.
This may sound somewhat more cumbersome, but it's really not. I haven't owned a "winter" jacket for over 30 years. Instead I use a windbreaker and put a wool sweater under it when it's cold. Try that some time, you'll probably be surprised how warm it is. If it gets even colder, I put on a polypro sweater first, then the wool sweater over that, then the wind breaker over that. So far I haven't been in conditions where that wasn't warm enough.
To me at least, the windbreaker-sweater combination feels less bulky and restrictive. Not only do winter jackets cost way more than a windbreaker and a sweater, but they don't feel as nice. And then you still need a light jacket for warmer but still cool weather. No thanks.
The advantage of layering is that it is versatile so for example if you have a base layer an insulating layer and a shell layer you can wear only the base layer in hot weather, base layer plus shell layer in mild but wet weather, base layer plus mid layer in cold dry weather or all of the above in extreme weather.
Soft shell jackets and lofted down or synthetics add even more permutations.
However, if you know that the conditions will be consistent then more specialist garments may be more appropriate for example in the arctic in winter the temperatures are predictably chilly and you aren't going to get rained on so a full body down and pertex suit may be the most efficient option.
Similarly in equatorial jungle insulation is entirely redundant and the humidity may make waterproofing a moot point.
There are also a number of alternatives to the layering system for mixed conditions for example the Buffalo Clothing System is based on one layer of pile and pertex worn without a base or shell and relies on a combination of wicking and ventilation to keep cool and dispenses with complete waterproofing in favour of good wet insulation performance.
Another alternative is the vapour barrier system which is based on caving gear and dispenses with breathability in favour of a completely waterproof shell which maintains a layer of damp but warm air around your body a bit like a wetsuit.
In practice it comes down to what works for you and allowing some margin for unexpected conditions a big part of the equation is what is comfortable in the range of conditions that you are likely to encounter some people hate getting wet and others hate feeling sweaty. Personally I go for a system which breathes well in most conditions and still insulates well when it's sopping wet this consists of : merino wool base layer (doubled up if it's very cold, pertex/pile jacket, cotton gaberdine or gore-tex shell depending on season)
