[Closed] What's warmer - wearing a heavyweight down jacket vs. 2 mid-weight down jackets?

Are we talking 'ethical down' or 'live plucked'?

Ethical of course! But same principal of both jackets were e.g. Primaloft

You'd need to look at sizing on the two jackets approach so the outer is a little larger - if the outer one compresses all the loft out of the inner one they won't be as warm as one that's got a lot of air trapped in it.

I'd think it'd just depend on how much down is in the jackets. Any extra air you trap between your 2 medium jackets will be relatively trivial and having thinner jackets may even mean the down lofts less well than the same weight of down in a single jacket, or that the inner jacket won't have a chance to loft fully.

What's longer - a long piece of string or two medium length pieces of string?

I have Mountain Equipment Annapurna duvet from many years ago. They were made so each larger size fitted closely over the one below (like Russian dolls). This meant you could adjust the layering depending on temperature. As far as I know it's not something that is done these days. As johnners says, the air gap probably has little or no effect.

thanks, Johnners looks like it'll settle the debate!

Assuming same weight of insulation in both instances, then surely one jacket is better

Cut would fit better, no compression of down from the second one. And lighter as less material to carry.

But two might be more versatile, and save having to buy new things

When I went to Lapland about 13 mths ago I was layering down gilet, buffalo smock and primaloft jacket. Then another big primaloft belay jacket over the top for standing around in the snow watching the northern lights

The plain answer is - it depends on the overall down quantity and quality, on air trapped in pockets, fit, collars, cuff and more.

The realworld answer is that two layers will be more flexible, if you are undertaking any activity and stopping (as most of us do).

If all you are doing is sitting, buy a sleeping bag.

My experience says two jackets are warmer. It's because there arent so many thermal bridges as thermal bridges don't line up in both layers. Even box-wall quilted heavy jackets have cold areas around zips and due to poor filling of the tops of some pouches.

Of course, it depends entirely on the circumstances. I was walking around Avebury on Sunday, wearing a merino vest, a tee shirt, a fleece and a Jottnar ultralight down jacket. I was just warm enough, I wish I’d had my old NF Nuptse with me as well, because of the wind chill. If the wind had dropped, I’d have probably been a bit too warm. Given the weather conditions in North America at the moment, an ultralight down jacket with a slightly larger 850 fill down jacket over the top would be my choice, because if things warm up a bit, you can always take a layer off, or just unzip each layer.

I think it would be difficult to get two down jackets to go over each other effectively without custom tailoring to make sure they dont either over compress or have wasted space.
Although others have said multiple layers I am not sure that rules out one thick down jacket over other items.
Since I cant think of many cases of down on down my guess would be the one thick wins (when worn over other layers). Having said that I am sure people will then find counter examples.

PHD do an expedition suit that is double layered - hate to think how much it costs.

Looks at website ...

Gets up from floor, that's "from" £1280 then.

Is the one on the outside wind proof? This is the biggest thing for me.

Wind proof outer and decent layering.