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Frank Perkins

Locale: North East
Re: Various clo questions, mostly for Richard on 09/04/2007 09:26:40 MDT Print View

"First, in calculating MET (based on the url you gave out earlier), I get a BMR of 1820 for me and 1281 for my wife."

I searched and couldn't find the link to calculating MET. Can you post the URL?


Jaiden .
(jaiden) - F
BMR url on 09/04/2007 09:28:04 MDT Print View


Frank Perkins

Locale: North East
Re: Various clo questions, mostly for Richard on 09/04/2007 09:37:46 MDT Print View

First, in calculating MET (based on the url you gave out earlier), I get a BMR of 1820 for me and 1281 for my wife. I divided by 24 (hours) which gave me 42.1 and 35.6 respectively

1820/24 = 75.8 Did you do the math wrong?

Jaiden .
(jaiden) - F
BMR, W/m2? on 09/04/2007 09:42:28 MDT Print View

I think I already see part of my problem. The BMR from that url is in kcals/day, but Richard shows BMR as W/m^2.

This confuses me somewhat, since the calculations on the url take into account body surface area. I tried converting kcal/day to Watts/hr but I get 881, and 881/1.95m^2 (my surface area, per the url) gives me 452, which is clearly wrong.

So, I still need help.

Jaiden .
(jaiden) - F
BMR/MET, ugh on 09/04/2007 09:45:30 MDT Print View

"First, in calculating MET (based on the url you gave out earlier), I get a BMR of 1820 for me and 1281 for my wife. I divided by 24 (hours) which gave me 42.1 and 35.6 respectively

1820/24 = 75.8 Did you do the math wrong?"

First, yes, see my last post. Second, I then divided by 1.8, which is the average m^2. Either way I think it's wrong in several different ways.


Joshua Mitchell
(jdmitch) - F

Locale: Kansas
BMR Calcs... on 09/04/2007 10:06:07 MDT Print View

If you take a look at the following exchanges, specifically my questions, it should help.

Realize that and out put of 1000 (kilocalories per day) = 48-49 watts. (1 820 (kilocalories per day) = 88.1351852 watts)

You're 'average' male has a resting wattage of 80.1 W. This is what Richards graph would likely have been based on. Whatever YOUR BMR winds up being, you can more or less correct the amount of Clo required by inverting the relationship. (aka people with higher BMRs require less Clo to stay comfortably warm)

Of course, this doesn't get into personal preference of what is considered 'comfortable'. These calcs should be used as a starting point.

Edited by jdmitch on 09/04/2007 10:07:16 MDT.

Jaiden .
(jaiden) - F
BMR getting closer on 09/04/2007 10:32:18 MDT Print View

OK, I think I've got the W/m2 now.

I found:
1 kilocalorie / hr = 1.16222222 watts

So my kcal/day BMR of 1820 divided by 24 hours, times the above gives me 88 and my wife 62. This divided by m^2 gives us 45.2 and 42.75 respectively. Not much difference, but I can vouch for a huge difference in our relative comfort levels.

John S.
(jshann) - F
Re: Re: Re: Also confused on 09/04/2007 11:04:51 MDT Print View

Touche' mon frere (?sp). Just trying to rile you CLOers up. Don't pay me no attention. I'll be over at the forums if you need me.


Edited by jshann on 09/04/2007 11:05:29 MDT.

Jon Rhoderick
(hotrhoddudeguy) - F - M

Locale: New England
Re: Re: Re: Re: Also confused on 09/04/2007 11:49:18 MDT Print View

Sooo I've done know how to do the calculations for the BMR now, but how do you do percentage of surface area? I saw a little of that lab report, but I don't really wanna read through all of it if someone could do the equation.

any help?

PS, we should get a copper mannequin for BPLs birthday or for Festavus.

Edited by hotrhoddudeguy on 09/04/2007 12:10:54 MDT.

Jaiden .
(jaiden) - F
how I calculated surface area % on 09/04/2007 11:57:39 MDT Print View

Well, I put all the measurements into a spreadsheet, adding left/right sides and then added them up for the total surface area. Then for each body part, I did a simple formula which divided the number for each part by the total. this gives me a % of the total, which I'm assuming is relatively standard, even if the actual area isn't. Then I add up the parts that make up a garment.

Here's the table I got, with some examples of items. I guessed that a hoodie with thumb holes covers 60% of the head (not the face) and 40% of the hands (not the fingers).

body part % area m2 % item %
legs 0.1771 0.120157406 pants 0.462107334
feet 0.0883 0.059909085 jacket 0.34968451
thighs 0.33 0.223895787 hoodie 0.415930524
crotch 0.174 0.118054142 vest 0.282515774
head 0.11 0.074631929
hands 0.0791 0.053667142
arms 0.099 0.067168736
shoulders0.1514 0.102720673
chest 0.138 0.093629147
back 0.127 0.086165954
1.4739 1

Jon Rhoderick
(hotrhoddudeguy) - F - M

Locale: New England
Re: how I calculated surface area % on 09/04/2007 12:22:48 MDT Print View

so is that the mannequin's measurements or yours? I suppose there would be large differences for each person, especially between the genders in the chest region.

Jaiden .
(jaiden) - F
Re: Re: how I calculated surface area % on 09/04/2007 12:44:00 MDT Print View

The mannequin's... I have better things to do than measure my surface area to 4 decimal places. I figure that though the area itself changes, the proportions probably don't very much. Besides, it doesn't look like she has much up top to skew the chest percentage.

William Webber
(micwebbpl) - F
Great Explanation, My Anecdotal Experience on 09/05/2007 10:19:41 MDT Print View

Basically you seem to be saying you don't need a lot of heavy clothing to keep warm! An R1 and Houdini are pretty minimal. Your chart is supported by my own experience in summer hiking to the High Sierra Camps in Yosemite (near Tuolumne), although I have some variations noted below.

Here are my personal variations:

I never hike in shorts and short sleeves - too much sun exposure for my taste. I use a sun umbrella from Go-Lite to keep the sun off me. This also doubles up as rain protection in a summer shower. I wear a long sleeve, silkweight Patagonia crew neck tee shirt (I think they call this Capilene 1 now). For pants I wear long pants, light Supplex nylon pants from Ex Officio, but hemmed high, about the length of knickers - to just cover the tops of my socks. This lets the air circulate over my legs. The long sleeve tee shirt is theoretically hotter than a short sleeve, but with the umbrella most of the heat is kept off me so it balances out. The "hot spot" I have is under the pack, but I try to use a Breeze from Go Lite and just shift it around to let one half or the other of my back dry out. I've been tempted to try one of the vent panel backpacks, but they are pricey.

The preceding outfit is plenty to keep me warm; on a summer high sierra hike, the only time I need to add anything is heading early out of camp, at dawn, when a nylon windshirt helps - I like the old, discontinued Wild Things Gear nylon windshirt, it isn't too hot.

If temperatures have been trending cooler, I will wear a zip neck, lightweight (Capilene 2, nowadays) long sleeve as my base layer, and back it up with either a Capilene short sleeve, crew neck tee shirt worn over in lieu of a vest, or a tank top Capilene (they have these from time to time). Finally, the windshirt. As you noted, it doesn't take much to increment the comfort level back up. If I am in an urban environment and its cold, each incremental layer has to be a lot thicker, but when I am hiking the incremental levels are a lot thinner - and the "warmth" generated by the higher metabolic level triggered by hiking tends to carry through after I reach camp, at leas for a while.

I end up carrying a second windshirt, a Houdini, as my rain gear. I try not to wear this unless it is raining, to preserve its water repellency. It isn't perfectly waterproof, but I follow the theory that while hiking I'll just be evaporating off any wet through anyway. This approach might not work in the fall in New England, but it's been fine so far at Yosemite.

I end up carrying a THIRD windshirt (good thing these are light!) as a "vapor barrier" for sleeping. I use one of the original Patagonia Dragonflys, notorious for their poor breathing, which in this context is a big help. It has a hood, and I wear this over my head, with or without a watch cap. I find the Go Lite Snow Cap a little hot in summer.

The one part of the equation I haven't nailed yet, is what to wear to bed to "up" the temperature rating of my quilt. I like to wear enough go to sleep with the quilt just over my legs, and then adjust the quilt up higher as it cools off during the night.

Quite frankly, the R1 hoody sounds very appealing as the "missing link" in my kit. It would obviate the need for a watch cap and Snow Cap; it looks good at the dinner table; and I could wear it under my windshirt around camp in a drizzle, or over the windshirt when sleeping (for the vapor barrier effect). So far I have been experimenting with synthetic fill vests and pullovers, and with heavier Polarguard like the Body Rug from Patagonia (a very high loft, equivalent I suspect to 300 but lighter in weight).

The only conclusion I have come to over five seasons of hiking, is that you need a different "kit" and approach for "active" trips and "take it easy" trips.

If you are going to be very active, with little time spent idling around camp outside of a sleeping bag, then every item of clothing needs to be much thinner. Silkweight for baselayer, R1 for insulation, a Micropuff Pullover for extreme insulation.

If you are going to go to Camp Curry in the dead of winter and rent an unheated tent cabin - as I have done - every item of clothing needs to be MUCH thicker - mid-weight zip neck tee, R2, down parka or thick synthetic parka. Otherwise the cold weather coupled with the inactivity will gradually suck the heat out of you and leave you miserable.

In any setting, though, layers seem infinitely better than just wearing a tee shirt for the sunny hike and carrying a thick down parka for camp, which is the main point of the post, I suspect.

Still, I like the elegant simplicity - lighweight baselayer, midweight (R1) hoody, windshirt. That's a slick analysis.

Phil Stetz
(pstetz) - F
Various questions, mostly for Richard on 09/05/2007 12:14:58 MDT Print View

Richard - This is great work. I've been following the thread for a number of days now and I've learned a lot about the details and science of staying warm. I have a few comments / questions:

1) Would you consider publishing the actual spreadsheet? Or re-posting a larger graph w/ a different background? I'm having a hard time reading some of the details.

2) What about wind chill? Would this factor into any of the equations? Or do we assume this is not a factor due to the wind shirt?

3) Gloves? Or do they only contribute to 'comfort' level since they are only covering extremities and not insulating the core? Same for a fleece hat. I suspect this would contribute more to warmth than gloves due to the blood vessels in that area. Or do we assume this is covered by the hood?

Thanks again for the great post. You saved me a lot of discomfort this weekend! I generally consider myself to be warm natured, but now I will bring some extra clothes for insurance.

Jon Rhoderick
(hotrhoddudeguy) - F - M

Locale: New England
Re: Various questions, mostly for Richard on 09/05/2007 12:22:03 MDT Print View

another two to add to that list of questions

4) what about lower legs, I dont think youd be very warm with a down jacket and supplex pants?

5) is the down jacket's loft single layer or double?

This thread is really starting to grow on me.

Richard Nisley
(richard295) - M

Locale: San Francisco Bay Area
The optimal clothing combinations for backpacking or hiking? on 09/05/2007 17:15:50 MDT Print View

Improved clarity clo

I will go through the posts and try and answer the outstanding questions in a subsequent post. But first, I wanted to address the common high level abstraction question. In other words, FEED A MAN A FISH, FEED HIM FOR A DAY. TEACH A MAN TO FISH, FEED HIM FOR LIFE.

The most practical way for a backpacker to determine the dry Iclu clo value for an ensemble is to measure the thickness of each garment component; multiply the thickness by 4 clo; and then multiply by the percentage of an average body it covers. Add these individual garment calculations together to calculate the Icl clo for your clothing ensemble. For high loft garments, the materials actual clo per inch can be used for a little higher accuracy but is not normally necessary for base layer garments.

The simplest thickness measurement is done by placing the garment on a table; placing one wooden ruler on top of the garment; measuring the double thickness with the other wooden ruler; and then dividing this value by 2 to determine the single fabric thickness.

The key standard mannequin values are 80% BSA for a one piece suit; 54.5% BSA for a hoody; 48% BSA for a jacket; 36% BSA for a vest; 22% BSA for a PFD or singlet; 7% BSA for shoes; 7% for complete head coverage; and 5% BSA for gloves.

Malden Mills makes 25 different variants of Polartec 200 fabrics. Malden Mills specs range from 13.5 oz per liner yard to 20.5 for the different fabrics. Compounding this variance is that each manufacturer can use different face fabrics and combinations of fleece types in the construction of a single garment. The overall thickness is critical in determining the thermal resistance of a garment.

The only completely accurate way to measure a garment’s dry Iclu clo value is on a thermal manikin in a lab. Each manufactures garments would have to be tested because each of the various combination of fleece and face fabrics used. A single garment test costs on the average of $600. Even if a manufacturer goes to the expense of measuring a garment’s Iclu clo, they rarely release that information. The manufacturers marketing department prefers to be differentiated on more defensible features such as brand name, colors, or styles. The North Face lists in their “Fleeces and Softshell” products 30 unique models for men and 33 for women. Every one of these garments would have unique clo values as would the range from every other manufacturer in the world.

The ISO 9920 international standard’s data base is excellent for conventional street clothes but is worthless for technical clothing used for backpacking. For example, the ISO 9920 standard lists the Iclu clo value for a down jacket as .55 Iclu clo. Even the 650 fill down jackets used by the Air Forces averages about 1.05” thick and are manikin tested at 2.2 Iclu clo. The 1 ½ thick 800 fill jackets are the standard for cold weather backpacking. The only way you will get the Iclu clo for the ensemble in your closest is by calculating it yourself.

Edited by richard295 on 09/05/2007 20:09:52 MDT.

Jim Sweeney
(swimjay) - MLife

Locale: Northern California
definition of terms. on 09/05/2007 19:24:26 MDT Print View

Here's a website that lists the definition of ICL (CL0), many other terms, and gives a program for computing required insulation (though this might be the site that Richard considers not that useful for backpacking):

I think this is an extraordinarily valuable thread, and many thanks to Richard, though I confess I'm not at all up to speed.

Richard Nisley
(richard295) - M

Locale: San Francisco Bay Area
Re: 2 Qs: Use of Icebreaker Nomad? Wet Correction? on 09/06/2007 07:34:45 MDT Print View

Joshua M. -

Q1: IB Nomad clo value?
A The short answer is the Ibex Shak is 390 g/m2 and measured .080 loft. The IB Nomad fabric weight is 320 g/m2 and measured .080”. 320 / 390 * .080” = .066” or a Iclu clo value that is 18% less than the Shak, which is the same as the R1 hoody.

The long answer is that determining the clo value of a stretchy technical base layer such as Merino wool, Power Dry, or Power Stretch is a little more complicated than other conventional insulation pieces like jackets and vests. For the R1 Hoody, the applicable ISO 9920 formula is Iclu = .43 X 10-2Acov + 1.4 Hfab x Acov which would yield a clo of .4. Acov is the body area percentage as a whole number and Hfab is the thickness in meters. When older style base layers, like cotton or wool, are tested on manikins, they closely match the formula. If you want to be conservative, just use this formula for your base layer.

I used an Iclu clo value for the R1 Hoody of .539 in my chart. I did this because my testing showed that the R1 hoody’s stretchy material and unique cut resulted in no fabric compression and an optimal uniform air gap at the skin. Also the uniquely tailored balaclava style hood was far better tailored and warmer around the neck and head than any other style I tested. Manikin testing doesn’t reflect the fact that the vessels in the neck and head don’t vasoconstrict like the rest of the body. So real world testing would be higher than the manikin test showed.

I kludged this formula for use in my chart to represent what I experienced.

R1 Calc

So if your IB Nomad fits every part of your body, including your neck and head perfectly, then adjusting from the high .536 Iclu clo value of the R1 Hoody makes sense. If not, use the more conservative ISO formula I provided above.

My testing showed that the Smartwool hoody’s hood and neck area had large billowing air gaps and so the standard ISO formula is applicable. My Ibex Shak was designed similar to the R1 for similar warmth. My Ragged Mountain hoody has a bad fitting neck area. The air gap fit is only an issue in the base layer. Having the rest of your layers fit with gaps doesn’t generally reduce the thermal comfort level.

The ISO formula above generally works well for base layers and conventional street clothing. For high loft insulation layers, the formula I previously provided works best (4 clo per inch x loft in inches x BSA%). As I mentioned previously, the accuracy is improved if you know the actual clo per inch for the material type and use this value.

Q2:…should one adjust these values if it's likely to be wet?

A2: For Merino wool and Polarguard, you should build in a safety tolerance. For polypropylene or polyester base layers and Primaloft insulation it isn’t necessary.

Edited by richard295 on 09/06/2007 07:43:25 MDT.

Richard Nisley
(richard295) - M

Locale: San Francisco Bay Area
Re: Also confused on 09/06/2007 07:59:35 MDT Print View

Johnathon R -

Q: Where are the clo values coming from?
A: For street clothes, the ISO 9920 data base. For technical base layers, the ISO 9920 formula for determining the clo value from the body surface area % (BSA%). For exceptionally engineered base layers such as the R1 Hoody, my testing showed that they were warmer than the ISO formula would indicate and so I created an additional formula. It should be noted that the ISO formula shows a .080 base layer hoody should provide .4 clo. The manikin tests ran by the Armed services on their clothing showed that there best base layer top tested .4 clo without a hood. So I don't think it is too much of a stretch for me to estimate the R1 hoody at .539.

After you have figured it out for your chosen clothing ensemble, please share with us how the numbers come out and how they compare with your real world experience.

Richard Nisley
(richard295) - M

Locale: San Francisco Bay Area
Re: Re: Also confused on 09/06/2007 08:09:27 MDT Print View

Matt F. -

I agree with you that 99.9% of hikers don't know the clo values of their gear and don't care. I would love to understand why they don't care. I suspect that it is because they believe that there is no EASY way to get the answer. What are your suggestions for how to better present this type of information so that more than .1% would find it beneficial?

Edited by richard295 on 09/06/2007 08:10:51 MDT.