A New Paradigm for Understanding Garment Warmth
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jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
re on 02/18/2011 08:06:17 MST Print View

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
(richard295) - M

Locale: San Francisco Bay Area
Re: Re: Re: Rab Jackets on 02/18/2011 08:16:54 MST Print View

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
(richard295) - M

Locale: San Francisco Bay Area
Jerry's Comment About Head Warmth on 02/18/2011 08:33:26 MST Print View

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

Edited by richard295 on 02/18/2011 08:36:40 MST.

Sergiy Sosnytskiy
(ssv310)

Locale: Ukraine
Re: Re: Re: Re: Rab Jackets on 02/18/2011 10:39:36 MST Print View

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 :)

Alan Bradley
(ahbradley)
vests weight efficieny also due to hight regulated core temperature (37C) on 02/18/2011 12:26:30 MST Print View

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.

Richard Nisley
(richard295) - M

Locale: San Francisco Bay Area
Re: Re: Re: Re: Re: Rab Jackets on 02/18/2011 17:47:00 MST Print View

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
(StephanCal)
Re: Re: Vests? on 02/18/2011 18:11:54 MST Print View

Roger,

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

a b
(Ice-axe)
All body surface areas are not equal in importance. on 02/18/2011 19:03:06 MST Print View

"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.Brr

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.

Edited by Ice-axe on 02/18/2011 19:23:37 MST.

Daryl Daryl
(lyrad1) - MLife

Locale: Pacific Northwest, USA, Earth
Insultex clo = 2.0 on 02/19/2011 10:55:52 MST Print View

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
(bpeugh) - F - M

Locale: Midwest
agreeing on 02/19/2011 11:20:42 MST Print View

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.

Edited by bpeugh on 02/19/2011 11:30:33 MST.

josh wagner
(StainlessSteel) - F
head on 02/20/2011 10:08:20 MST Print View

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
(richard295) - M

Locale: San Francisco Bay Area
Re: head on 02/20/2011 21:43:44 MST Print View

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
(StainlessSteel) - F
:( on 02/20/2011 21:55:29 MST Print View

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

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: :( on 02/20/2011 22:05:53 MST Print View

> 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
(StainlessSteel) - F
no rog on 02/20/2011 23:00:16 MST Print View

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
(Ice-axe)
The lunatic fringe are "nose breathers" on 02/20/2011 23:16:21 MST Print View

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
(--B.G.--) - F

Locale: Silicon Valley
Re: The lunatic fringe are "nose breathers" on 02/20/2011 23:21:25 MST Print View

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

--B.G.--

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: The lunatic fringe are "nose breathers" on 02/21/2011 02:49:32 MST Print View

> 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 Daryl
(lyrad1) - MLife

Locale: Pacific Northwest, USA, Earth
Face Mask on 02/21/2011 09:52:22 MST Print View

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
(Ebotshon) - F
Chart Vs. Stated CLO Values on 09/07/2011 14:31:35 MDT Print View

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?