Yeah, fleece all the way for me. If you've a windproof layer with you too it's only really packsize and about 150 g that you are saving. Hiloft and gridded fleeces are amazing. I got through -20 C ice climbing by swapping my normal fleece (Eider thing, but basically an R1 with full length zip) for a Rab boulder one (Thermal pro).
Fleece is more durable, cheaper, deals with sweat better, and feels nicer than insulated garments too. One other thing you could consider instead is something like the Mountain Equipment Switch, which is super breathable but also insulated fairly well.
Just seen the hipbelt on the Osprey rucksack. There's no way that should cause much abrasion problems. I use an Aiguille sack with a similar simple hipbelt with the same jacket and after two years mine is still looking as new.
I'd send it back - I've the same top and it's bombproof. It's been up gritstone chimneys, thrown about, and seen a fair bit of Chamonix granite and no real signs of wear.
If they won't accept it back (I'd be surprised) then the Paramo Fuera is seriously tough, but it is cut like a bin liner. The Ventile and Buffalo windshirt suggestions above will be even more durable but perhaps a bit heavier.
...However, that neglects the fact the air is a poor conductor, so the energy transfer is still dominated* by energy conducted from the body, by the fabric, and by the water itself.
* Body and air will both be radiating to the water, so it would be interesting to compare the radiated energy transfer against conducted energy transfer. My gut feel is that conduction dominates at those temperatures.
This is hideously complicated... Yes, I'd thought that as they were roughly the same contributions given their respective temperatures. That means radiation will be the same, but I'm not sure of the relative contributions of radiation and conduction here. The conduction from air would indeed be lower than through the fabric, but then this starts to depend on how wet the fabric is too...
I am sure our paths will cross at some point and we can put the world of baselayers to rights over a beer or two!
Sorry for completely derailing your thread, Wayne. I think a meco baselayer would be a good investment and that you'd notice the benefit.
Tenohfive, I think I agree with much of what you say, though I am cautious about calling merino 'warm when wet'. I actually wrote a blog post about that too (sorry! https://gearandmountains.wordpress.com/2014/05/23/warm-when-wet/) and though that was geared towards down versus synthetic, some of it still applies. I think merino is certainly a lot better than cotton, but because it absorbs that much more water than synthetics I don't think it's that warm when wet, just because it takes ages to dry. However, its wicking means it might certainly be better than something like a soaking wet Helly Hansen. The thicker baselayer is certainly worthwhile if you don't think you've much chance of overheating, as then the extra insulation is worth it. I suppose I'm writing from my own experience where I don't think there's many days I've been out in the UK and haven't got a bit too hot at some point: if your baselayer is thinner there's less chance of this happening than if it's thick.
Captain, the point regarding 'indirect evaporation' - good term, or at least follows my back-of-a-fag-packet term(!) - is a good one, and something I hadn't really thought all that much about to be honest. It's worth noting that the evaporative effect is less than 'direct evaporation' because some of the thermal energy will now come from the environment, rather than the skin: if it's 30 °C, about half of the energy for evaporative heat loss will come from the air, not the body. In colder weather, however, the body's will contribution will obviously be far greater.
I knew this baselayer thing would be a can of worms, but it's a good debate.