A New Paradigm for Understanding Garment Warmth

[Woubeir (from Europe)]

Actually, this is a kind of graph I would like to see in the BPL wiki with regular updates to reflect current available pieces. I've started writing for a local outdoor magazine and I'm planning to write an article about insulation comparing fleece with high loft insulation. Most people overhere still buy fleece when they want something warm and I would want to introduce high loft insulation. This graph would seem like a perfect idea for comparing both without making things to complicated.

[Dan Cunningham]

This is fantastic information, and I love the way it's put together. Standing ovation.

In fact, I just made a purchase today based on it – I opted for the MB Down Inner Jacket instead of a the Thermawrap after seeing how much the difference in insulation was on your graph. Thanks!

[Brad Rogers]

Yes, Thanks to you Richard I am now rethinking my insulation systems. It looks like the Mont-Bell UL Inner Down Jacket is really warm for it's weight. I think I need to pick up the jacket and the pants.

BTW- Does anyone know anything about the new Cocoon stuff? I would love to know the approximate clo and weight. As well as a anticipated release date.

[Allen Jacobs]

Just want to add another newbie "thank you". This definitely helps me out. I’d like to think that examples like this will help me understand some of the other more technical discussions on here as well.

[Michael Febbo]

Huzefa, you are going to have to help me out with your chart- I have no idea how to translate that as a means to deduce the proper down fill for a specific garment.

If 9 ounces of 800 fill power down is not optimum for the Permafrost (I assume you mean it is underfilled?) then what would be the ideal amount. 9 ounces is used by Nunatak (Kobuk) and Feathered Freinds (volant) in similar jackets, and I assumed it was standard for a good belay parka.
This is not academic to me- my DAS will die next season and I am switching to down.

P.S. I hope this doesn't sound combatative, but the kind of information being offered in this thread is what I would like to see formalized by BPL, and it's lack is why I let my membership lapse. I feel that I gain more information on the forums than through the articles… just some feedback for the site.

[Lynn Tramper]

Sure would be nice to slip a Nunatak Skaha hoody into that graph. Very nice work as usual Richard.

[Huzefa @ Blue Bolt Gear]

The table I posted is infact Richard's work which I copied from his old post but I forgot to mention that.

Quoting Richard again: "If you opt for 800 fill down baffles filled for optimal thermal density, they will out-perform (>oz/inch/yd2-green, >clo/in/yd2-red, >clo/oz/yd2-blue) the best synthetics when dry. If you opt for max loft only, you will have better oz/inch/yd2-green (eye candy) but you will not have a higher clo/oz which is the most critical measure for backpackers."

Permafrost has 2" loft, clo of 5.33 or 2.665/in and as you say has 9 ounces of 800+ down. You will need 2.46x time down i.e. 22.1 oz of total down to achieve its potential of 6.562 clo/in or 13.124 clo.

That would be too warm for your needs. Unfortunately no one makes garments to achieve max warmth/inch and max warmth/oz as they require radical designing which is too costly to manufacture. Also most people equate warmth to loft so its bad from business perspective.

My suggestion is to not worry about this since such products dont exist and let Richard's chart help you with your selection.

p.s Sorry, if I have confused anyone.

[Ashley Brown]

Unfortunately no one makes garments to achieve max warmth/inch and max warmth/oz as they require radical designing which is too costly to manufacture.

I would disagree somewhat. All that is required is to use smaller baffles and stuff more down into them — so you get a density which is closer to optimum. For instance, you could shove a whole lot more down (3 times as much?) into the MB inner jacket without needing to make the baffles bigger. Then you would have a very warm jacket without needing to make a bigger, heavier shell to hold it. Easy.

Of course, Huzefa has identified the reason manufacturers don't do it… loft sells. If one jacket looks puffier than another it must be warmer right? Guess which one the average joe is going to purchase?

[Chris Townsend]

Over stuffing down garments actually produces clothing that is not as efficient warmth for weight. The optimum amount of down is that which can loft fully without being too loose. Once the down cannot loft fully there is no advantage in adding extra down.

I also think that thickness is a good general indicator of warmth. It's not the only one of course but I think it is important, despite what some are saying here. Shell fabrics, baffles and radiant barriers all play a part but thickness is key.

[Ashley Brown]

Over stuffing down garments actually produces clothing that is not as efficient warmth for weight. The optimum amount of down is that which can loft fully without being too loose. Once the down cannot loft fully there is no advantage in adding extra down.

I understand that this is the generally accepted view. But Richard Nilsey has some very persuasive data which shows otherwise. In particular, it appears that down can be stuffed at about 2.5x the density that it is normally done, whilst still getting full value for warmth. The idea that down needs to "loft fully" so that it spreads out as much as possible is not correct (again, according to Richard's data and some published papers). Having said this, there is a point at which adding extra down starts to produce smaller gains, and eventually you even go backwards. But there is a linear region where warmth increases proportionally to the amount of down (even if it is "overstuffed").

I don't have the links to the threads where this was all discussed, but if you have a search through Richard's posts in the past year you will find them. Have a read, it is very enlightening!

[Ashley Brown]

Hey Chris, in case you haven't seen them here are the threads I was referring to (well, 2 of them anyway). Here's the original thread and there are some further comments in this thread which clarify a few points.

[Anonymous]

"In particular, it appears that down can be stuffed at about 2.5x the density that it is normally done, whilst still getting full value for warmth."

What effect, if any, would higher density stuffing have on
breathability and moisture buildup/drying time?

[Chris Townsend]

I accept that down can be stuffed at more than the density used by many makers (though not all – Rab and PHD with some products for a start – PHD will add down if requested) which is why I said overstuffed. There comes a point at which the weight added by extra down isn't justified by any increase in warmth. Of course down doesn't need to spread out as much as possible. Indeed it can't unless an item is very under stuffed. By "lofting fully" I mean to the optimum amount for the maximum warmth for that amount of down.

I've used down bags that were definitely under filled, leading to cold spots as the down could shift too easily. The apparent loft before use wasn't actually there over the whole bag.

I still maintain that thickness is a good general guide to approximate warmth for those – the majority I'm suspect – who don't want to go into technical details.

[Chris Townsend]

Ashley, I've read the threads and some of it makes sense. I'm not convinced that in the real world these figures really make sense however. And I'm always interested in what happens in practice. To give two examples regarding the compression of insulation. Testing inadequate sleeping bags that didn't live up to their temperature rating (something I've done too often) I've used down jackets to boost the warmth. I've found that wearing the jacket in the bag isn't very efficient if it's a tight fit. It's far warmer to spread the jacket over the bag so it isn't compressed. Now maybe I've always had jackets with optimum density of fill – if so there's quite a few of these about as I've used a variety of jackets from different manufacturers. I've also squeezed down bags into bivvy bags a little too small for them and found that this cut the warmth despite the extra barrier of the bivvy bag. I was warmer sleeping on the bag rather than in it. Overall my experience is that allowing insulation to loft to its maximum provides the most warmth.

[Ashley Brown]

By "lofting fully" I mean to the optimum amount for the maximum warmth for that amount of down.

According to Richard's data there isn't really an optimum amount of loft for maximum warmth… rather, there is a linear region where the shell can be compressed or expanded without affecting garment (or sleeping bag) warmth.

Anyway, the interesting thing about it is that you can go a lot further than "overstuffing" a sleeping bag by 2oz. You can in fact usually double the amount of down without losing value for warmth (I think Richard have have actually tested this on a generic mummy bag).

Richard pointed out some examples at the beginning of the thread where the thickness of the garment does not correlate much at all with how warm it is. I would say that the amount of down fill (assuming same quality) is probably the best approximate and simple measure of a garment's warmth. You can't always read that on the label though.

[Ashley Brown]

I'm not convinced that in the real world these figures really make sense however. And I'm always interested in what happens in practice.

Yep, fair enough. If it's your experience that a jacket placed over a bag is warmer than in it, then you can't argue with that. Whatever works best in practice is king. There may be something else going on in those situations you describe. Perhaps the down is not compressed evenly.

It would be interesting to hear from Richard whether he has tested it on a real sleeping bag. Here's some data he posted in one of those threads, but I'm not sure where he got it from. Note the clo/kg of down doesn't change as you increase the fill:

[Adrian B]

"If it's your experience that a jacket placed over a bag is warmer than in it"

One factor is that the jacket will be compressed underneath you when worn, not when placed over you. But this might not be significant, and perhaps countering this is that I find it hard to get all of a jacket usefully covering me without wearing it.

And of course it's not a factor in a too-tight bivy bag situation, where Chris still observed the lesser-compressed bag being warmer.

[Lynn Tramper]

>I would say that the amount of down fill (assuming same quality) is probably the best approximate and simple measure of a garment's warmth.

I thought this was a generally accepted principle of insulation design. The more fill=the heavier insulation=warmer bag. But all most of us need to know is what is the (accurate) warmth rating of the bag compared to it's weight? I choose WM bags because, *underfilled* or not, I find their comfort rating to be accurate and their bags to be light.

[Chris Townsend]

Of course the problem with real world experiences is that there's always something else going on! Any anecdotal statement is always missing some factors. However it is in the real world that bags and jackets are used to keep warm.

Those figures are interesting. I'd like to know where they came from. 12oz is a significant amount of down.

[Richard Nisley]

Bob (Dennis-Your question is incorporated in the last paragraph)

I have been up in the Sierras for a few days and am now just getting an opportunity to start responding to questions. First I want to say I was very impressed with your responses to Will's article on "Salomon Tundra Mid WP Insulated Boot Review". Your posts were courteous, well structured, and compelling in the support of your position… great job.

You said, "Can you tell us more about what makes for a better rating"? The fleece and synthetic insulation vendor's clo/oz ratings closely correlated with their relative performance vis-à-vis one another. The down insulation results closely correlated with the down fill amount. All insulations do a good job of blocking convection. Blocking radiation losses is the biggest variable between the synthetic insulation types and as well as the impact of down density. Based on my tests, fleece and synthetic specifications appear to be based on the inclusion of a still air layer on the outside of the insulation in addition to the insulation itself. When layering garments, frequently this still air layer won’t be present and the ensembles won’t be as warm as you would anticipate. Sizing of each layer to have at least a 6mm gap between them is necessary to approach the insulation vendor’s published clo/oz values.

You said, “When a manufacturer comes out with a "new and improved" version next year, how do we know whether or not it still occupies the same place in your table? And if not, then where it belongs?” The situation with garments and sleeping bags in the US is the same as it was with sleeping bags in Europe prior to the EN 13537 standard. In other words the consumers aren’t provided adequate information to make an intelligent decision. I suggest buying from vendors who have a reputation for honest representation of their products specifications and then try and find the closest match to something which has already been independently tested by multiple sources. It is in the interest of most manufactures and their advertising partners to use FUD (fear, uncertainty, and doubt) to discredit the value of independent testing. The only manufacturers who would benefit from having independent tests published are the one who products test best.

You said, “How do I determine where a garment not in your table fits in?” You can extrapolate from the existing test results. For example, in a post subsequent to yours, Dennis Park asked, “By any chance, would you know where Mountain Hardware's Compressor men's jacket would fit on your chart? Oops, forgot to mention 2007 model.” The 2007 Compressor specs were size medium [Weight] 16 oz [Shell] Superlight 15D, [Insulation] PrimaLoft One 115 g/m2. That is the same insulation type and a similar amount to what was used in the WT PL1 hoody that I tested. The Wild Things Primaloft One hoody used 2 layers of 60 g/m2. This jacket would theoretically test out with an intrinsic clo of approximately ~1.46. In other words, it is ~1.5 times warmer than a Polartec 300 weight or a Patagonia Micropuff pullover or jacket.

[Richard Nisley]

Ashley,

Thank you for the kind words. I guess that the first time I looked at the question of 300 weight fleece versus the Montbell Light Alpine question; I interpreted vendor specs to arrive at a conclusion… sorry if I screwed up the first time. This time around I actually tested each of the products myself.

[Richard Nisley]

Huzefa,

I used a guarded heat plate. It measures the cumulative heat conductivity from all modes of transmission (conduction, convection, and radiation). The measurement technique integrates the measurements in the seam, along the ramp up/down, and max loft area.

The average clo was 6.18 divided by 1.5 inches for a less remarkable value of 4.12 per inch. A stack of cotton cloth yields 4 clo per inch and so the warmth is less of an anomaly than is the clo/oz.

The Fugu failed in the market place and is no longer available. I don't think people appreciated the jacket's extraordinary value proposition because New Balance wasn't a known performance jacket vendor in the UL community.

[Richard Nisley]

Brad,

Yes the Patagonia Polarguard Delta 2.7 oz/yd2 Pullover is the previous version. The current version uses 3-oz Climashield® Green continuous filament polyester (40% recycled).

[Richard Nisley]

Brett,

I haven't measured those garments but my GUESS concurs with your assessment.

[Huzefa @ Blue Bolt Gear]

I think you missed my point.

Here is a quote from an old post of yours -"The Fugu down jacket is 800 fill and the Cabelas down jacket is 650 fill. They are sewn through construction. 1 1/2" is the maximum loft. The baffles average 5" wide. Only approximately 2" of the 5" is at the maximum loft. 1 1/2" on either side it ramps up from a few mm to 1 1/2". My crude estimate is that the average loft is about 70% of the max or 1.05"

clo at max loft = 6.18
average loft = 70% or 1.05"
average clo = 70% or 4.362

Wouldnt you consider average clo as the effective clo value of the garment?

[Author]

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