A New Paradigm for Understanding Garment Warmth
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Ashley Brown
(ashleyb) - F
Re: fugu really that warm? on 02/21/2009 23:24:37 MST Print View

The difference between the permafrost and the Fugu is that the Permafrost has a much heavier shell. The Permafrost has "only" got 9 ounces of fill but weighs 25 oz. So presumably it is designed to be pretty bulletproof. The Fugu, on the other hand, weighs 13-14oz I think but has a much much lighter shell... so it's possible it may have more down in there or at least a similar amount.

But yes, pretty amazing! Goes to show you that sewn-thru baffles aren't that great in comparison to having extra down.

Read an earlier post from Richard about the jacket (scroll down).

Ashley Brown
(ashleyb) - F
Re: Re: fugu really that warm? on 02/21/2009 23:25:43 MST Print View

Snap, Roger. Gee I hate it when people say things more succinctly than me and post it while I'm still composing!! ;-)

Michael Febbo
(febbom)
permafrost on 02/21/2009 23:27:24 MST Print View

You're right, the materials will add weight- though the Permafrost should be very warm for its weight given its welded box construction, 9 ounces of 800 fill down, and rather thin shell (15 and 30 denier). It's actually not tough enough for me, which is one reason I have stayed away from it. Still, it appears that the radiant liner of the Fugu is of greater value- warmth wise- than more down fill...

Huzefa Siamwala
(huzefa) - M
Re: A New Paradigm for Understanding Garment Warmth on 02/22/2009 02:14:04 MST Print View



This means neither Alpine Jacket nor Permafrost Parka are filled at optimum down density.

Edited by huzefa on 02/22/2009 02:14:37 MST.

Adrian B
(adrianb) - MLife

Locale: Auckland, New Zealand
Powerstretch on 02/22/2009 02:51:00 MST Print View

This is a fantastic graph. Suprising to me is how high powerstretch is up there, I wish it had less elastine (12%) which (I believe) makes it slower drying. It's also a bit fragile (the mountain hardware Zip top I had was anyway).

Woubeir (from Europe)
(Woubeir) - F - MLife
Re: A New Paradigm for Understanding Garment Warmth on 02/22/2009 04:32:27 MST Print View

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
(mn-backpacker)

Locale: Land of 12,000 Loons
Great Info on 02/22/2009 18:37:49 MST Print View

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!

Bradford Rogers
(Mocs123) - MLife

Locale: Southeast Tennessee
Insulation on 02/22/2009 20:50:18 MST Print View

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
(jacall) - F

Locale: North Texas
RE: A New Paradigm for Understanding Garment Warmth on 02/23/2009 06:51:18 MST Print View

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
(febbom)
Someone help the idiot on 02/23/2009 10:42:32 MST Print View

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
(retropump) - F

Locale: The Antipodes of La Coruna
Re: RE: A New Paradigm for Understanding Garment Warmth on 02/23/2009 11:57:47 MST Print View

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

Huzefa Siamwala
(huzefa) - M
Re: Someone help the idiot on 02/23/2009 14:48:05 MST Print View

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
(ashleyb) - F
Re: Re: Someone help the idiot on 02/23/2009 16:01:33 MST Print View

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
(Christownsend) - MLife

Locale: Cairngorms National Park
A New Paradigm for Understanding Garment Warmth on 02/23/2009 16:25:27 MST Print View

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
(ashleyb) - F
Re: A New Paradigm for Understanding Garment Warmth on 02/23/2009 16:48:57 MST Print View

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
(ashleyb) - F
Re: A New Paradigm for Understanding Garment Warmth on 02/23/2009 16:57:54 MST Print View

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.

Edited by ashleyb on 02/23/2009 16:59:13 MST.

Tom Kirchner
(ouzel) - MLife

Locale: Pacific Northwest/Sierra
Re: Re: A New Paradigm for Understanding Garment Warmth on 02/23/2009 17:07:44 MST Print View

"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
(Christownsend) - MLife

Locale: Cairngorms National Park
A New Paradigm for Understanding Garment Warmth on 02/23/2009 17:14:23 MST Print View

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
(Christownsend) - MLife

Locale: Cairngorms National Park
A New Paradigm for Understanding Garment Warmth on 02/23/2009 17:30:35 MST Print View

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
(ashleyb) - F
Re: A New Paradigm for Understanding Garment Warmth on 02/23/2009 17:32:03 MST Print View

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.