> How on earth is a mid layer that doesn't keep you warm but allows breathability versitlie.
A mid layer should be just that; a mid layer, to go between a base layer and an outer layer. Its purpose is to trap a layer of warm air close to the body, to provide insulation, whilst allowing mositure to escape freely.
Adding a windproof outer shell to a layering system is, IMHO, the best, and cheapest way of improving your comfort on the hill.
If it's warm and still, you wear a base layer
If it's warm and windy, you wear a base layer and windproof shell on top
If it's cool and still, you wear a base layer and a suitably warm midlayer.
If it's cool and windy, you wear a base layer and a suitably warm midlayer, and a windproof shell to stop the warm air being blown from the midlayer.
If it's raining, you decide whether your windproof will provide adequate water resistance, and, if not, replace it with your waterproof.
You can choose the weight of midlayer to suit the weather conditions; lightweight for warmish weather, heavier weight for cooler weather.
You can pick the windproof to suit the activity; lightweight for walking, more robust for scrambling and climbing.
You can replace each of the items as they wear out.
You can wash and proof each layer as appropriate.
A windproof fleece with a fixed membrane has little versatility:
you can't change the level of insulation;
the insulation is used inefficiently, as half of it is outside the windproof layer (generally);
the membrane doesn't allow moisture to escape easily;
you can't use only the windproof layer;
you can't remove the windproof membrane for use under a waterproof;
you can't replace each layer separately;
you can't care for each layer separately;
they're relatively bulky and heavy;
they take a long time to dry.
> I certainly wouldn't advise wearing a windproof fleece under a waterproof jacket
No, neither would I; two layers of poor breathability would result in a rather sweaty captain.
> So Mike do you seriously believe if you went to the Lakes this weekend and you wanted to climb Scafell or Helvellyn and Sundays prediction is rain and cold that you'd be okay with a 100 fleece and a wind smock that weighs 90g?
That would be the 'action core' of my usual 4-layer system, yes:
1 - base layer
2 - 100 weight fleece
3a - nikwaxed, hooded pertex windproof
3b - lightweight waterproof in case of heavy rain
4 - lightweight Primaloft (60g) duvet in case of sub-zero temperatures or prolonged stops
I left the waterproof behind on a trip up Pen-y-Fan a couple of weeks ago; heavy rain and cold unlikely, and the Litespeed windproof easily held off the light rain we encountered.
Edited: 03/05/2007 at 17:36