Bought a down jacket last year on sale, but it has turned out to be a) of a bad quality and b) simply too cold. So I am looking for a better model now.
I'm doing hill walking in the highlands, including peaks with crampons and ice axe in winter, and in the future may also be active in the alps (will sadly move away from Scotland next year). Would also like to have a try at ice climbing some time. The purpose of the jacket is to keep me warm on breaks on the peaks in winter, possibly while belaying, and in case the weather turns really, really bad (blizzard conditions). Usually I'm reasonably warm in a baselayer and fleece when on the move. So the jacket will spend a lot of time in the backpack.
I have made a list of models that I like visually (yeah, yeah, don't judge ...) and can afford, but I find it difficult to estimate how warm they are - I tried the last one I bought in store and thought it to be warm, just to find out later that really it isn't. That jacket was 600 CUIN fill power, weighted 390g in total, but the fill weight isn't shown. I'm even cold in that jacket in the city below 5°C, and on the mountain it's just about okay in good conditions with a fleece underneath.
Now I am looking, for example, at the much better quality Jöttnar Fenrir, which boasts 112g of down filling with 850 CUIN, and a total weight of 380g - better than my last jacket, but I have a feeling that that won't be enough.
So my questions are:
1. How warm a jacket do I need for my uses? Let's assume a common worst case scenario of -5°C on the Munro peaks with strong winds >50 mph. Jacket worn over base layer and micro fleece, and under a hardshell (to keep the down dry).
2. Can jackets of different fill weight and fill power be meaningfully compared? E.g. could one say that if
Jacket 1 with 100g fill and 800 CUIN has a hypothetical 'warmth coefficient' of (100 x 800/1000 = 80, and
Jacket 2 with 200g fill and 600 CUIN has one of (200 x 600)/1000 = 120, then
Jacket 2 is 50% warmer than
Jacket 1?
Then the list would be like this:
Jöttnar Fenrir (112g fill weight/850 CUIN): 95.2
Montbell Alpine Light (135g fill weight/800 CUIN): 108
Norrøna Lyngen (170g fill weight/750 CUIN): 127.5
Mountain Equipment Dewline (191g fill weight/700 CUIN): 133.7
Montbell Frost Line (200g fill weight/800 CUIN): 160
Mountain Equipment Lightline (296g fill weight/750 CUIN): 207.2
I quite like the ME Dewline (even though it has a pretty low fill power for the price) - do you think it would be warm enough for Scottish winter use?
I know I'm being a bit complicated here, but since it's difficult to find out how warm a jacket really is in store, and my last purchase was a flop, I'd like to get it right this time