A New Paradigm for Understanding Garment Warmth

[Bill Reynolds]

I just got a new MB Ex Light jacket. I have an older 2005/2006 725 fill UL Inner jacket. I haven't worn the new one yet but was looking for comments regarding the relative warmth of one to the other. The EX is 3 oz lighter in XL but it is hard to believe it could be as warm or warmer than the UL Inner. I have worn the inner on some cold nights and stayed warm. It would be particularly helpful to hear from someone who has owned both ( the older UL Inner and the new 900 fill EX Light) Thanks in advance.

[Bill Reynolds]

Anybody?

[Mike M]

I never owned the UL Inner (but do have the Exlight)- you want to look at fill weight vs overall weight- most of the savings in overall weight are construction (no pockets, etc ) and material 7d vs 15d

then it comes "down" :) to 900 vs 725- there is a formula floating around that shows how much impact the quality of down makes

I have heard from folks that have had both, they thought the Exlight was as warm (some thought even warmer) than the UL- maybe one of them will pipe in

[Richard Lyon]

I have them both, and thought that the EX Light was warmer, thanks to the 900 fill down. I had serious problems with the EX Light's zipper (it eventually broke and I had to replace the jacket) and fabric, which was a long way from being down proof. I should say that my EX Light was one of the earliest on the market, and I understand that newer models have been more reliable. My Down Inner is the parka, which has a hood, a feature I really like. If buying today I'd probably go with the Down Inner.

[peter vacco]

ahhhh .. all this timei thought polarstretch was toastier than polartech 100. now we know.
a long time, and we are talk'n about 3 decades ago, Fletcher wrote at length about warmness., and to some extent this included a bit about poofyness (my word), and how some insulations feel warmer (and ARE) because they not only insulate, but poof up to exclude cold air from entering into where You are.
this to me is the major reason those down jackets made of so-very-light material seem so toasty.
poofy pushes out the cold. what remains is heat. (that's right.. isn't it ?)

[alex lucovich]

Hi y'all … I'm new to the site but I've been reading posts for the past month – very informative!
I was wondering if I could get some advice – I'm looking for a down jacket w/ at least 800 fill power (preferably 850) & w/ a high fill weight (6.5 – 8 oz). I'm not extremely concerned w/ every little oz. of the total weight but it definitely has to bundle up very tightly when in my pack & be somewhat light.
The NB fugu seems ideal but its not available in my size – I'm considering the rab infinity – it is light w/ 7.4 oz of 850 down & is actually 50g less than the advertised 510ish grams (hope that doesn't mean 50g less of down).

Any other suggestions?

[Richard Nisley]

Alex,

Based on the criteria you specified, the Rab Infinity is the fourth most suitable. The three jackets ahead of it, in rank order, are Feathered Friends Helios, PHD Yukon, and the Sir Joseph Koteka. The fifth most suitable is the least expensive and is the CAMP ED Jacket.

[alex lucovich]

Thank you Richard!
I think I've narrowed it down to the helios, yukon & infinity. PHD doesn't advertise its fill weight although it is 900 fill power. Would you be able to estimate its fill weight & those 3 jackets' clo values? I'm wondering whether the numerous cold spots on the infinity will substantially reduce its warmth (although will be excellent for protecting the down from shifting). The infinity also seems to be able to pack the smallest but I could be completely wrong on that.
Thanks again =)

[Richard Nisley]

Alex,

Helios – 8.00 oz., 4.78 Iclo
Yukon – 7.85 oz., 4.90 Iclo
Infinity – 7.41 oz., 4.56 Iclo
PHD – 7.85 oz., 4.90 Iclo

The average person can only detect a variance in a jacket's insulation in increments of .5 clo and so all of the aforementioned jackets will feel the same to you, assuming a good fit.

The secret to maximizing the efficiency of sewn through baffle garments, such as the Infinity or Helios, is to size either your wind shirt or hard shell to wear over it. The v shaped spaces between the baffle seams and the outer material of a wind shirt or hard shell create insulating air gaps that offset the loss of insulation at the seam.

The rank order I provided in my prior post was based on the ratio between warmth and weight / volume.

[alex lucovich]

Richard, to say that you're a wealth of info would be a huge understatement – thanks for all the advice! I feel a lot more comfortable now making a purchase. =)

[Yoann Larguier]

Hello,

I'm french so sorry for my english… I was reading your messages, and I was wondering about the clo for Rab jackets such as : Photon Jacket, Generator Jacket, Xenon Jacket and Generator Alpine Jacket.

Do you have an idea ? I tried to calculate it, but the result is not correct.

Thank you in advance,
Yoann

[Richard Nisley]

Yoann,

Rab Photon Belay Jacket 3.92
Rab Photon 2.66
Rab Generator Jacket 2.27
RAB Xenon Jacket 1.51
Rab Generator Jacket Alpine 2.27 (Has a 60 g/m2 hood but assume a similar hat for the Generator Jacket)

[Ryan C]

I picked up a Rab Microlight Vest for a decent price and it seems pretty warm. What would the clo be for something like that? How about the Microlight Jacket? Thanks

[Richard Nisley]

Ryan,

Both the Microlight jacket and vest have an Iclo of 2.22. The Iclo values are to compare garments in the same class. Since the vest class only covers 75% of your body surface area, it will only be 75% as warm as the jacket class with the same insulation per unit area.

[Yoann Larguier]

Waow !!
Thank you very much !

Do you know a way to calculate approximately the "temperature of comfort" or the "limit temperature" of the jackets (as for sleeping bags). The only one way to calculate de "temperature of comfort" is with : T=31-0,155 P * R with T in °C, P in W/m² and R in clo, can I say : "The jacket can help me to be confortable up to :"

Or should I say :
with a micro-fleece of 200g/m² (weight=275g size L, clo=0,76 ?) and a merinos wool long-sleeves of 210g/m²(weight 260g size L, clo=0,16 ???), I have CLO = clo_jacket + clo_fleece + clo_merinos

Jacket alone Jacket + fleece + merino
Rab Photon Belay Jacket 3.92 -5,5°C clo=4,84 -14,0 °C
Rab Photon 2.66 6,3 °C clo=3,58 -2,3 °C
Rab Generator Jacket 2.27 9,9°C clo=3,19 1,3 °C
RAB Xenon Jacket 1.51 17°C clo=2,43 8,4 °C
Rab Generator Jacket Alpine 2.27 9,9°C clo=3,19 1,3 °C

If it's "right", is it for you a temperature for "comfort" or for "limit" ?
Thank you very much in advance !
Yoann

[Sergiy Sosnytskiy]

Hi Richard,
You give Rab Generator Jacket a value comparable to that of Montbell Alpine Light. The latter is much loftier (I think, at least twice) and, in my limited experience, feels warmer. What is the reason they have comparable Iclo?

[Eric Blumensaadt]

It appears, from my experience and from winnowing the information from several posts, that garment loft is a relative issue, even using the same type of insulator.

Two identically constructed jackets filled with down TO THE SAME LOFT THICKNESS, one having 850 cu. in./oz. of down and the other having 650 cu. in./oz. of down will insulate differently in actual on-trail use with a pack.

The pack harness and back pad will compress the wonderfully light 850 fill down more than the "lesser" 650 fill down. Everybody knows about how well high count fill down compresses. That's great for packing it in a stuffsack, not so great when wearing under heavier or more restrictive shells and especially under a pack. You lose more insulation with the "higher cu. in./oz." down with the same compression/sq. in. compared with "lesser" down.

So maybe we need to re-think what fill weight is most satisfactory if a down garment is to be worn with a pack.

Just sayin'…

[Stephan Doyle]

Richard,

I am unsure if this information exists anywhere. Forgive me if I have missed it.

What is the relative clo value of a vest of comparable loft, down and shell fabrics compared to a jacket?

I know there may not be a simple answer. However, how much warmth are we getting, scientifically, from our down vests?

FWIW, I'm thinking of my WM Flight Vest in particular. It looks like it's a sleeveless version of their Flight Jacket. Comparable insulation value over the core, but with gaping holes where the sleeves should be.

[Roger B]

Stephen I am not sure if this is what you are looking for but from earlier in this thread

Richard says
"The relative warmth between garment types within the same family (down or synthetic) can be easily approximated. This assumes the typical case where the garments all use the same fabric and insulation areal weights (for example 100g/m2 PL1 and 15 denier ballistic nylon). The average body surface area for a parka is 52%, a jacket is 48%, and a vest is 36%. A vest will keep you 75% as warm as the comparable jacket, because 36 /48 = 75%, and compared to the parka it will keep you 69% as warm. A vest is generally the most efficient insulating item you can add to your clothing. To illustrate this BSA phenomenon, as discussed above, the Montbell Thermawrap synthetic vest provides 75% of the total insulation that the jacket provides yet, the ratio of garment weights is only 63%. This phenomenon holds for all insulation types."

also

"The garment's torso is tested with a guarded hot plate to ascertain its insulation value. I tested a Patagonia down Sweater vest and determined its intrinsic clo was ~2.31. I also tested a Patagonia down Sweater Pullover hoody and determined its intrinsic clo was ~2.31. The insulation, fabric, and construction although slightly different between the garment types, yielded the same ~intrinsic insulation value. Total clo, for each garment, is determined by multiplying the intrinsic clo by the body surface area that it covers. The average body surface areas (BSA) covered by different garment types are as follows:

Hat 4%
Shoes 7%
Balaclava 8%
Pants 43%
Shirt or Jacket 48%
Hoody 54.5%
One Piece Suit 80%
Sleeping Bag 98%

If you want to compare the total clo between two dissimilar garment types (for example the Fugu jacket and the Permafrost Parka), multiply the intrinsic clo value times the BSA for each garment to determine how they compare. The Fugu total clo is .48 * 6.18 = 2.97. The Permafrost total clo is .55 * 5.24 = 2.90. The hood on the Permafrost is huge but a down balaclava, in combination with the Fugu would easily beat it for greater warmth at less weight, save the relative durability issue."

My apologies if you had already read these posts

[Richard Nisley]

Sergiy,

The Rab Generator uses PL1 insulation and the Montbell Alpine Light uses 800 fill power down. Loft is only a rough comparator if the two jackets have the same insulation type, the same density, and comparable fit.

If the Rab Generator Jacket feels warmer to you, my only guess is that this garment fits you better at the openings. If you have gaps at the neck, wrists, or torso then the chimney effect will purge the warm air from a garment.

[Jerry Adams]

All body surface area is not equal

Head is more important than torso than arms and legs

If you're cold, reduced blood flow to arms and legs will cool them off, so there will be less heat leaking out there

[Richard Nisley]

Yoann,

You also have to factor in your MET rate to determine what level of insulation will keep you comfortable. This old foum thread may be helpful:

http://www.backpackinglight.com/cgi-bin/backpackinglight/xdpy/forum_thread/9378/index.html

[Richard Nisley]

The physiological factors that are a result of slow onset hypothermia, such as vaso constriction of the limbs but, not the head, are discussed in detail here:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=13697

[Sergiy Sosnytskiy]

Richard,
No, Montbell Alpine Light feels warmer to me than Rab Generator, and the difference seemed to be more than than the difference in figures. Though, now I am confused. I will try to compare them again :)

[al b]

Doesn't the fact that only the bodys core is temperature regulated to 37 degrees C mean that bodywarmers(vests) are more weight efficient, because there will be a bigger difference between ambient and body temperatures, hence vest insulation here has a greater effect.

Presumably, hats have a similarly 'boosted' effect, as I dont think you can cut blood supply to your brain when cold.

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