A New Paradigm for Understanding Garment Warmth

[Richard Nisley]

Sergiy,

Look at the very first post in this thread, it shows the clo value for the MB Alpine Light, it has a higher Iclo than the Rab Generator; so, the MB Alpine Light should feel warmer as you confirmed.

[Stephan Doyle]

Roger,

Thank you, that was exactly the type of response I was looking for. I must've missed it.

[a b]

"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"

I have been thinking about this thread a lot while training in the cold rain these past days.
I have to agree with the above statement. Even though the head has a relativeley small BSA it is responsible for a very much greater amount of heat loss due to the blood flow very near the surface of the skin.
When it comes to being comfortable I and quite a few of my friends(judging by the insulating garments they wear) have found that keeping the Torso, Head, Hands ,Feet, arms, and legs warm in that order of importance to yield the best results.
If someone locked me in a meat locker naked and offered me one piece of clothing at a time I might chose differently say: Torso,feet,head,hands,arms,legs due to percieved immediate comfort.
Either way the head is very much more important to preserving heat than it's 4% BSA would indicate.

I have to add though that i am tentatively on board with the CLO ratings VS simple measures of loft in regards to warmth.
I recently added an MLD spirit quilt with APEX insulation to my gear and have been testing it alongside my WM ulta-light down bag.
The 1.75" of measured loft of my APEX is as warm as the 2.5" measured of Goose down loft.
I used them both as a quilt at temperatures from 38 degrees to the low 50's. At least in my subjective determination they are equally as warm.
The other factor is the momentum fabric of the MLD quilt has greater warmth to the touch. It even seems to warm up quicker but this could be due to the lack of quilting that allows less dead airspace than my down bag.
I was about as stubborn a "loft is warmth" guy as there ever was but lately my experience with APEX is changing my mind.

[Daryl and Daryl]

I'm sitting here with a large piece of insultex draped over my head. The specs say this paper thin piece of foam looking material has a clo of 2. That would put it pretty high on the clo charts and above 300 fleece.

Hmmmmm, I'm going to have to ponder this one. I sure don't feel as warm as I would with a 300 fleece blanket draped over me and this insultex stuff is sandwiched between two layers of remay type fabric….which should make it a little bit warmer yet.

Daryl

[Brett Peugh]

I would agree with Matt in that if my head, hands and feet are covered well and pretty warm I can go a lot colder or with less insulation on my arms, legs and torso. But I am really tall and the extremities are even moreso.

I know that Andrew Skurka really liked using an Apex insulation quilt over his Alaska trip and did not notice much if any loft loss over the course of it.

[josh wagner]

curious. a question about the numbers and statistics that say people lose the majority of heat through their head….

is that heat loss through your skin (same as the rest of your body) or do they calculate the percentage of heat that escapes through the big holes in your body in the head (mouth, nose, ears, eyes). i would think that those gateways into the body's interior would EASILY be the sources of the greatest heat loss.

if that were the case, then the priority of covering one's body with insulation would have to change due to the inability to cover those holes (or the importance of gear like a hat that covers the ears or a balaclava would increase). i can see a down turban in the future!

can anyone provide any clarity or insight to this?

[Richard Nisley]

Josh,

Your 10 -12% nose and mouth heat loss is covered under the category of respiration heat loss and is a separate category from the body surface area dry heat losses.

The “United States Naval Flight Surgeon's Manual: Third Edition 1991: Chapter 20: Thermal Stresses and Injuries”. It states, “Vaporization of water removes heat from the skin surface and the moist mucous membranes of the respiratory epithelium. When one gram of water is converted into water vapor, 0.58 kilocalories of heat must be supplied from the surroundings for the conversion to occur. Although the actual amount of heat loss depends on the ambient relative humidity, in Antarctica, where humidity is very low, respiration alone may account for ten percent (375 kcal) of an individual's total daily heat loss. Insensible perspiration, as is shown in a later section, accounts for an additional loss of about 400 kcal.” Note the 10% value for Artic respiration.

70 Kcal/hour is effectively the same as the 70.77 Kcal/hour BMR value used in the ISO 8996 (2004) International standard. Most physiology models list the constituent components of heat loss as 12.5% (= 8.8 Kcal/hour) respiration, 12.5% (= 8.8 Kcal/hour) insensible perspiration, and 75% dry heat loss (= 53.1 Kcal/hour).

[josh wagner]

richard,
i appreciate your answer. do you think you could explain that to me like i'm a 4th grader?
thanks

[Roger Caffin]

> like i'm a 4th grader?
:-)

If your head cools by 1 C then your body work very hard to restore the temperature of your head – at almost any cost.
If your arms or legs cool by 1 C, then your body says … ho-hum.

Does that help?

cheers

[josh wagner]

hehehe. i appreciate the thought that went into that, but it doesn't clarify my post a couple above this. concerning heat loss through the holes in the head (mouth, nose, eyes, ears).

[a b]

Okay.. I am a new member of BPL so take it easy on me but….
For a long time I have noticed that breathing through my nose even while hiking has advantages over mouth breathing under extremes of cold and heat.
Remember I was born and raised in California so if my theory sounds whacked out it's because I am.. er it is.
Here goes:
Under cold conditions when the air is also very dry breathing air through the mouth causes stress on the lungs and increased dehydration and cooling of the core.
Breathing through the nose under similar cold/dry gives the nasal turbinates time to humidfy and warm the air as it is inhaled and recapture some warmth and humidity on the exhale that would be lost out the mouth otherwise.
Similarly in very Hot conditions breathing through the nose cools massive amounts of blood in the nasal passages and therefore the head and brain versus mouth breathing. Also nose breathing in Hot dry conditions reduces dehydration by scavenging moisture from the lungs and using it to humidfy incomming dry air in the nasal passages.
If you are still with me.. I have found i use less water when i force myself to nose breathe even if it means moderating my pace to allow for it.
While it is not always possible to breathe solely through the nose at higher activity levels (such as Colorado's CDT) I found that i can "train" myself to do so for a significant part of the time while climbing uphill.
I believe nose breathing doubles the distance i can hike on a liter of water before reaching the same state of dehdration as mouth breathing.
I have no hard science to back up my belief.. but I did stay at a Holiday Inn express once.

[Bob Gross]

See if you can cross your nose breathing for temperature with pressure breathing for high altitude.

–B.G.–

[Roger Caffin]

> I have found i use less water when i force myself to nose breathe even if it means moderating my pace to allow for it.

Yup. Happens that way.

Cheers

[Daryl and Daryl]

So, for retention of heat, breathing thorugh some type of face mask probably helps.

In cold weather I like to use one anyway because it feels better. I don't like cold air going down my windpipe when I'm breathing hard. It sometimes makes me cough.

Daryl

[Eric Botshon]

According to Primaloft, Primaloft One has a clo value of 0.92

The patagonia nano puff uses 60g/yd -> 2.12 oz/yd which if my understanding is correct would give this garment's insulation a clo of 1.95

This would be as warm as the MB Down Inner. The MB Thermawrap Parka has 80g of exceloft insulation and is rated at .77 on your chart.

Why is this?

[Dustin Short]

Look at the dates. Those charts are nearly 2 and half years old. You'll notice the Patagonia uses Polarguard (PGD) and not primaloft. A lot has changed.

Primaloft recently (within the past year) updated the clo of all their products. Some new manufacturing process is my guess. They actually were rather generous and simply replaced all their old products with the improved products instead of differentiating lines and charging more…

Anyway PL1 used to be rated lower (0.89 if memory serves me). Also remember these are MEASURED clo values. The MB and Patagonia both use sewn through construction which decreases clo. Also manufacturer specs aren't always most accurate, with testing conditions usually being optimized to max out the clo value…

Hope this helps.

[M L]

I don't quite understand… if you look at Richard's other chart and the chart on top, it appears that I will be more than warm if I wear the Fugu jacket and nothing else on a 0 degree while sitting still. Something seems odd… Am I misinterpreting something?

[James Klein]

I didn't dig up the other graph but I am pretty sure I remember the one you are refering to…

The one at the top of this thread gives Iclo (intrensic clo) for various garments. This is the insulation value nominalized for surface area (a 1"X1" square of the jacket would have the same Iclo but much much smaller clo.

The other graph (if I remember) had clo required vs temperature with MET rate traces. The clo required is the total clo of all clothing. If you had the iclo's of all your garments you would have to multiply each by the %body covered and add them together to get clo.

You would need a fugu bodysuit to stay warm at the temperature and activity level.

[Link .]

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=9378

[M L]

Oh, ok… makes sense. I was adding up clo for some of my clothing and it was not adding up to the required clo for the activity level… I forgot about the legs and head…

[Richard James]

Outstanding jacket and good value. It weighs (and packs to) almost nothing and kept me warm on a trip to the Alps with temps in the 20's. Pair this with a lightweight waterproof shell and you probably won't need anything else for most endeavors.

[gao qian]

hi richard
do you have same parameter about EB MOUNTAIN GUIDE HOODED DOWN JACKET.
thanks

[Richard Nisley]

4.35 iclo

[gao qian]

thanks for your quick replay,
this iclo Below my expectations.
so could you tell me the WM vaper and WM meltdown.
the iclo about meltdown is with hood or not?
thanks again

[Patrick Young]

Richard,

According to pata cs this series of garments uses the same amount of down as
the down sweater and hoody. Would the clo be the same give that down density
Also is a contributor to that overall value or have they compressed it too much?
Thx
Pat

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