We are heading for colder weather and I am continually amazed how little people know about Warm clothing. Some seem to think that the heavier the better, yet the best expedition clothing, worn to the coldest places on earth weighs surprisingly little.
Let's start with an executive summary. Good quality down is about twice as warm as the best synthetic insulation, which is about twice as warm as a good fleece, which is about twice as warm as wool. All approximate and all weight for weight.
Insulation comes from trapping small pockets of air. Evolution has developed goose down (which is different to feathers) to be the very best, this is because geese live in very cold conditions, but their insulation needs to be light weight so that they can still fly.
Despite using down in duvets for centuries it was not until 1940 that Eddie Bauer patented the down jacket, that is now standard wear in most of the world's cold regions.
But not all down is equal. How good it is can be measured by fillpower. This is a number. USA and European fillpower numbers are measured differently, as a result for any given number the European measure is warmer. USA 600 fillpower is where down starts to be good. Only the very best elite garments in the world make it up to 900 fillpower and only one manufacturer (that I know of) has made it up to 1,000 European, which will be about twice as warm for its weight as the USA 600. If a down garment does not tell you what fillpower it is using just don't buy it, they are hiding how bad they are.
Down is very durable, it lasts for ever. But it has an immense problem, it reacts very badly to being wet. Basically it forms clumps and provides no insulation. It is incredibly difficult to dry out and unless you follow special procedures the clumps remain. Many times I have seen people wearing down jackets in the rain that have gone totally flat, doing more harm than good. You can buy down jackets made of waterproof material or wear them under a waterproof. This fails when your own condensation soaks the jacket. So down is really only practical when worn in sub zero conditions.
The USA military have to be prepared to deploy large numbers of people to live and fight outdoors in the world's worst weather, so insulation is important to them. But the shortcomings of down make it largely impractical. In typical American fashion they threw money at the problem, in scientific research. This resulted in Primaloft, which still provides good insulation when wet and which dries out very quickly. However it has a problem in losing its loft, and therefore its insulation, over time. A regularly worn 2 year old jacket will be noticeably less warm than a new one. Never put Primaloft clothing in stuff sacs. Now there have been developed many competitors to Primaloft but it is well worth researching what you are buying as some synthetic insulation is pretty useless.
Both down and synthetic insulation have to be built into a series of pockets in order to make a garment. Sew through quilting is the lightest and cheapest way to do this. Box quilting is more expensive but appreciably warmer as there are no cold patches. Synthetic insulation can be woven together in such a way that it requires only the minimum of quilting.
This brings us to fleece, this was pioneered by Polertec and has been much copied. There is an immense difference between cheap high street fleeces and the real thing, even within Polartec there are several products of different qualities. The main problem fleeces have is that the wind goes straight through them, so they are best worn under another layer. Fleece worn as an outer layer isn't doing much good. Some fleeces have membranes in them, so at least the inner half is working when they are worn as an outer layer. Avoid these, it is a half baked concept and you will only suffer condensation.
You can buy jackets, one piece suits, socks, gloves and hats using all the different forms of insulation. I really like gilets as they look after core temperature without impairing movement and they layer well.
So now we come to brands. The best outdoor clothing brands are not high street names. My favourite are Patgonia, Arcterix and Haglofs. For down clothing very good brands are Marmot, Rab and Mountain Equipment. You can buy all of these in total confidence. However if you want the very best warmth to weight ratio then you can only go to PHD (Peter Hutchinson Designs), as used in countless expeditions to the world's most hostile places. Hand made to measure yet surprisingly affordable, because there is no middleman, you buy direct. Their huge range includes garments that are comfortable for sustained use down to -55C. And if you want to go colder than that you can just add an extra layer!