/ Lack of insulation measure of down jackets

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henwardian - on 13 May 2014
I just spent a number of hours trying to find a replacement for my old dying downie. After a bit of googling around and comparing, it came to me that THE main purpose of a down jacket is to insulate; everything else is secondary.

This being the case, the most important measure should essentially be a volume of insulating air trapped by the down. I.e. fill power multiplied by mass of down in the jacket. Though I realise that the actual volume created by the down is going to be a lot less than this ideal, it is at least a start.
Comparing this measure to the overall weight of the jacket would also be useful; divide insulating volume by mass of jacket to get a measurement called somthing like "insulation power" (Yeah, alright, I'll leave the name with marketting!)

Now the gripe: Down jackets do not state this, you have to manually go through the specs with a calculator and work it out. Worse still, a great number of jackets will tell you nowhere on the internet what mass of down they actually have in them.

So, why are there no manufacturers using this information as a selling point?! I've read a thousand selling points today from velcroed sleeves to hydrophobic down to narrow gusseting but it is all secondary guff which (while it might be useful or neat little features) is collosally less important than the basic insulating properties of the jacket.

I'd be happy if someone pointed out something obvious that I'm missing here.
tjin - on 14 May 2014
In reply to henwardian:

Overall weight of the jacket, says nothing about insulation. They are making the jacket material lighter and lighter, so the overall weight might just indicated a heavy shell, not the insulation.
TobyA on 14 May 2014
In reply to henwardian:

> something obvious that I'm missing here.

Surely the construction technique is as important? A jacket could have a very high "insulation power" by you reckoning but if its sewn through you'll get cold spots that a box wall jacket with less power won't have. The latter is likely to work better because of that.

fire_munki on 14 May 2014
In reply to henwardian:

Shame there can't be some sort of crash test dummy, starts of at X degrees and then in a controlled environment the time taken to reach y degrees is measured.

Bit like the hydro static height thingy-ma-bob for hard shells.
galpinos on 14 May 2014
In reply to henwardian:

It's not just down quality and quantity but construction (as Toby says) and fit.

A well fitting box wall jacket of lower quality down with less fill will be warmer than a big, baggy stitch-through job with more high quality down.

A neat little number won't get the above info across....
purplemonkeyelephant - on 14 May 2014
In reply to henwardian:

All things considered, if you're that concerned about things like fill weights you would be better off going into a store and trying a few on. As others have said, there is much more that goes into an insulated jacket than numbers, but the importance of these things depends on whether you just want it for around town or if you're heading to the south pole. For me fit is king, every brand does a super warm jacket, but if there are huge dead spaces in the fit it won't feel too warm at -30...
Mr Fuller on 14 May 2014
In reply to henwardian:
This has to be the most interesting gear post (to me at least) I've seen on UKC in ages. Sorry for what has turned into a mammoth reply.

The fill power (FP) multiplied by the mass (M) of down (FP x M = "insulation power") equation is actually used by quite a few manufacturers, but by none of the big ones. It tends to be used for sleeping bags more than down jackets, too. Cumulus, for example, use it.

The units of your "insulation power" value are simply volume (inches cubed (yuck)) so it's probably better to call it insulating volume, and that's what some of the manufacturers call it. Some of Backpackinglight's forums are awash with this sort of thing but unfortunately they sometimes forget other key factors that influence the THERMAL performance of a jacket:

1) the fit. This is so important and few people think about it. If you are bellowing and chimneying heat out at the hem, cuffs, and collar then you might as well not bother. Similarly, if the jacket is so tight that you compress the insulation then it is a waste of time. For me, the Arc'teryx Atom synthetic jacket is completely brilliant because it fits me perfectly. The Cerium down jackets, however, are worthless to me, because they are too narrow across my back leading to compression of the insulation and subsequent thermal bridges that will make your back cold. You simply must try on insulated jackets and if they are too loose or too tight then don't buy them.

2) the design. As other posters have mentioned, the construction techniques play a big part in how the jackets perform. Box wall or trapezoidal jackets (big dollar) are warmer than stitch-through because the insulation is more evenly-distributed, there are fewer cold spots, and the jacket is also more compression resistant. More here: (check out the down jacket with the infrared camera - heat pours through the stitching). Overlapping areas of fabric make a jacket warmer but openings make them cooler. Open pockets can often allow masses of heat out.

3) the face fabrics. A very windproof fabric will allow no air through which sounds good...? Maybe not. In high winds the fabric will compress the insulation and drive out the warm air. A slightly-permeable fabric may be better as it will allow a bit of air through, making the filling less liable to compress. The stiffness of the fabric also influences this.
4) other stuff. There's a lot more things too, but they are the big factors. What if the baffles surrounding the down are too big/small...? Could down be at the wrong density...?

The thermal performance, however, is not the only factor to consider with an insulating jacket: remember durability, features, fit, appearance, ethics, etc all play a part.

I think manufacturers really really should state the weight of down they put in their jackets, and most do. And I think the FP x M = "insulation power" equation is very useful to know, if you ensure you compare like-for-like with sizes (S contains less down than XL, obviously). However, it's not as simple as buying the one with the biggest number, especially when the fill powers or fill weights might be out by a fair bit in some of these products.

When buying a down jacket I'd make a longlist based on the 'insulation power' equation and which manufacturers I think make good down kit then would go to a shop and try on as many as I can, ruling out 80% because they don't fit or I don't like them based on features. That would probably leave one or two jackets and I'd probably buy the cheaper one or the bright-coloured one!

Fire-munki, they do sometimes do this sort of testing but it is very expensive. Thermal manikins often cost £100,000+ and are notoriously hard to use and easy to break. Most manufacturers simply cannot afford the testing or do not prioritise it. Tog testing is a lot simpler, cheaper, and easier but tests fabrics and down, not the features. A thermal camera (£10,000) combined with tog testing is a good halfway-house, but user-trials are every bit as important.
Post edited at 13:25
henwardian - on 14 May 2014
In reply to tjin:

My reference to overall weight was as a ratio of insulation power to overall weight. Not overall weight alone which, you are correct in saying is not a useful number in and of itself.

In reply to others:

Ah, I hadn't really considered construction that carefully. I have noticed that a lot of lighter jackets and more modern ones have narrower pockets for the down relative to my old one but I did not think about stich through and box constructions and the effects of cold spots. Thanks for pointing that out

I realise that fit is important and trying jackets on but as Mr Fuller says, it is useful to have all the information you can get to narrow down the field before you get to trying them on for fit because this is really the last stage in the buying process.

Without a dummy and tests, there is no real way to tell how warm a down jacket is when trying it on though. Standing in a shop just isn't a test. If I stood on a mountain at 5 degrees on a blustery day with no sun, THEN I might have an idea of how warm each garment actually feels.

Realised from your comments that quotes for the insulating volume could be fudged by cramming too much down into too small a pocket in the jacket but I would hope that kind of rubbish would be below outdoors manufacturers who want themselves to be taken seriously (and ofc it would make the whole garment heavier).

Though they have their flaws, the "comfort to -20C" type of ratings on sleeping bags are a hell of a lot better than nothing at all regarding insulation. If jacket manufacturers could come up with some tests and agree a similar standardised measurement I'd be pretty happy to see that.

I don't really rate the face fabric as so important in a down jacket. I don't expect it to be waterproof because that's what I wear a waterproof jacket for. I would also expect (could be wrong here) that the loft of the down is what keeps the garment from being compressed by wind and that if the fabric were made stiff enough to keep its shape in strong winds, it would also become cumbersome and difficult to move in.

I guess some of these concerns depend on your intended use for the jacket. I sometimes rock climb in mine when it is cold and often belay in it. Perhaps if you do more winter related stuff you have other concerns (like waterproofness) when buying.
Mr Fuller on 14 May 2014
In reply to henwardian:

Yeah I'd like to see, if not a standard test, at least some numbers to indicate how warm the jacket is, even on what might be on what for most people would be an arbitrary scale. Tog tests would work and Exped, Multimat and Thermarest all quote tog values on their mats and these can be directly compared: perfect. Jackets are more complex, though, and the tog test works less well for them. Despite this, if you see 8 togs on one jacket and 5 on another, unless the 8 togger is extremely badly designed or fitting, it is always going to be warmer. That would be nice to know. I've tested some of my own clothing on our tog testing rig and the values I've got have correlated exactly with how 'warm' I think the kit is. I'd love to buy a shedload of jackets, test them all, then send them back to the shop.
purplemonkeyelephant - on 14 May 2014
In reply to henwardian:

Also the output of the activity you are doing is so important. When pursuing a super lightweight approach to a polar goal, Ranulph Fiennes took very lightweight gear, but offset this by the amount of heat he would produce pulling 450lbs of gear behind him. When they stopped, they set up a tent. Yes he suffered a lot, but it's important.

When I started out I wanted the warmest down jacket available, but the store advisor pointed out I would only need it perhaps 3-4 days a year. I bought a lighter weight synthetic jacket and use it all the time, even during active walks in extreme cold.

Perhaps if the jacket is too efficient it will be too warm for the season. Being realistic about the real end use will determine good value, rather than spending money on a jacket that cooks you, and isn't very packable. This is where weight/compressibilty vs warmth starts the age old battle.
TobyA on 14 May 2014
In reply to henwardian:

> Though they have their flaws, the "comfort to -20C" type of ratings on sleeping bags are a hell of a lot better than nothing at all regarding insulation.

Testing belay jackets at -20 over the last few years has made me a bit sceptical about how much use such a measurement would be because the conditions you wear clothing in tend to be more wild than those where you sleep in a sleeping bag. So a jacket can be great when it's -20 but might be a bit pants when its sleeting, roaring a gale and -1.

Ok so the rating could be for still air and controlled humidity but you could still end up with funny results i.e. a jacket that wasn't much cop for Scotland getting -20 while a good belay jkt for soggy Britain being rate to -1 or something. The rating wouldn't really help much for someone off for a week in the Cairngorms!
DancingOnRock - on 14 May 2014
In reply to henwardian:

henwardian - on 15 May 2014
In reply to TobyA:

I can see your point but I still think a standardised test would be a big step up from no test at all. I think you pick a set of test criteria which mirror as closely as possible a sort of average of conditions where a downie would be used.

Down jackets are supposed to stay dry, i.e. Either be covered with a waterproof shell or used in dry weather. Ok, in reality they do often get damp/wet but the same could be said of sleeping bags after a couple of days of rainy weather and tent condensation. So I'd say the test should be done in dry conditions.

Wind is a bit trickier because the fit of the jacket round any test dummy then becomes important and in reality everyone is a slightly different shape. I'm not sure what I would do about wind speed.

Humidity is a tricky one. I'm sure that varying humidity has an effect on how fast cooling would occur but I would be a bit surprised if the relative performances of different jackets varied much with humidity (until it reaches a level where the jacket gets wet of course). I'd probably say "plump for some average humidity of 50%" or something.

I guess the alternative to all this would be to test under a half dozen different sets of proscribed conditions with specific winds, humidities and temperatures and then take an average of all these results. Quote the average and leave the marketting departments to use any individual results, e.g. "our new Fort William jacket scores exceptionally in humid windy conditions!".
Mr Fuller on 15 May 2014
In reply to henwardian:

I wrote a bit about the differences in conditions on staying warm here:

As for the impact of humidity, yes it does make a difference but it's not necessarily that important. All lab testing is carried out at 65 % RH.

I'd love to see more of the testing that you describe, if only to get people more interested in the science but the problem is the lack of budget for this sort of testing.
andrewmc - on 15 May 2014
In reply to henwardian:

Aren't all down jackets necessarily windproof anyway (in order to keep the down in, as down is very fine)?
Mr Fuller on 15 May 2014
In reply to andrewmcleod:

Windproof is a sliding scale. If you have a hurricane blowing then pretty much any textile will let air air through it. To be downproof a fabric must have an air permeability of less than something-or-other (can't remember the figure). Gore-Tex (not the new one) has an air permeability of zero so is totally and utterly windproof, but something like Pertex, despite being downproof, has an air permeability well above zero, meaning it lets air through in very strong winds.
itsThere on 15 May 2014
In reply to henwardian:

Would this not only hold true if half the volume twice the fillpower is equal to twice the fill power half the volume. This isn't true as fill power is not linearly related thermal insulation coefficient of something.

We know wind chill is not linear vs temp and wind speed. So how can you use volume of insulated air when pertex quantum and drylite perform differently. Thus screwing the vol of insulated air as a performance metric.
henwardian - on 17 May 2014
In reply to itsThere:

> Would this not only hold true if half the volume twice the fillpower is equal to twice the fill power half the volume. This isn't true as fill power is not linearly related thermal insulation coefficient of something.

I'm not sure what you are saying here... Do you mean that the insulation coefficient of a volume is also dependent on fill power of the down used to fill it?

> We know wind chill is not linear vs temp and wind speed. So how can you use volume of insulated air when pertex quantum and drylite perform differently. Thus screwing the vol of insulated air as a performance metric.

It is a fair point. As people have pointed out, no performance metric for something as complex as a down jacket is going to be perfect but I still think that the insulating volume is a useful measure.
PPP - on 18 May 2014
In reply to henwardian:

I'm just afraid that such measure might be misleading for less experienced users (given that experienced users will have little difficulties comparing two jackets). Even today, we have two ways to measure Fill Power - the US and non-US (European maybe?). The US rating has 50~100 higher result that the other one.

Also, we don't want manufacturers to skip hidden details like cords, zips, etc. Some features are clearly visible, but I imagine that it is possible to hide some missed features. For example, my Marmot Precip hard shell has mesh lined pockets which are terrible. Especially when I carry 26 keys for work. Or a sleeping bag with shorter zip. People who want ultralight gear will notice these things, but regular customer does not really need that level of lightness. Otherwise, we will end up with cling filmed down...

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