A REVISED PARADIGM FOR ESTIMATING GARMENT COMFORT LIMITS

This is very interesting and useful! Thanks!

I am new to this type of calculations and I have a question to make sure I understand the calculation of the gaments iclo from the insulation’s clo on page 4:

0.39*0.52 = 0.2028

Is the insulation’s clo given i table 2, the clo that the insulation would provide if your whole body was covered with the insulation with that specific weight per sq-yd?

The relationship between clo and iclo has always been confusing

that example (0.208 = 0.39*0.52) explains it simply and clearly, thanks

if your whole body was covered by the same insulation, then clo = iclo

Hugh,

You said in part, “I would have thought a full set of cap 4 thermals (ie including pants) would be more than warm enough to keep me thermoneutral at 70F – but it would obviously be less than 1 iclo .
why do these two ways of deriving the iclo of the “base ensemble” generate such different results?”

Thank you for your question; it made me realize I should have addressed this more clearly in the pdf document. I have since revised it to answer this question. It is on page 2 and entitled THREE EXAMPLES OF 1 CLO – AIR LAYER ENSEMBLES.

Gunnar & Jerry

You are both substantially correct.

Just a minor point to remember: until the final surface boundary layer is added in, the values are both intrinsic. One is the intrinsic value for the insulation and the other is the intrinsic value for the garment.

Ok, I think I understand that. If I then dare to refrase my question to something more pecise it might be:

The Iclo values given in Table 2 represents the possible Clo contribution of a layer of the insulation to the tolal Clo, if the whole body is covered by the insulation in a layer with the stated weight per sq-yd. This is on the condition that (a base ensamble is used beneath and) a boundary air layer with an air flow barrier is applied on top of it as required by the model. The other layers may or may not be part of the same garment as the insulation layer

(Just to make sure I hava a correct understanding now.)

I now also read the latest addition about the base ensamble, thanks for that useful addition. It becomes clearer that to what I think of as my base layer I in many (most?) cases need to add garments to get the base ensamble of the model.

O.k., so you look online at a garment you’re thinking of purchasing. How does one determine the CLO of the garment? That’s the part I am not yet understanding.

Thanks,

Pau

Paul,

You said, “…you look online at a garment you’re thinking of purchasing. How does one determine the CLO of the garment?”

Look in this pdf to see if it is one I already tested. If not and it is a synthetic garment, the manufacturer should provide you the insulation type and the g/m2 of the insulation. For an uncommon synthetic insulation, not listed in my pdf Table 2, you can typically find this value by a Google search. All the remaining steps are listed in this pdf.

If it is a down garment, the manufacturer should provide you the insulation type and the oz of fill. Use this to convert a down garment’s clo that I have tested and listed in Figure 7 or in the link following Figure 7. For example, say I tested a 900 FP hoody with 2 oz of fill and its Iclo was 2.5.  A newly introduced hoody with the same type of fill, but double the ozs, would be double the Iclo. I always listed the insulation Iclo in addition to the Camp chores thermo-neutral temp during my approximately 10 years of posting my test results to BPL. If you can’t find a down reference in my pdf, do a Google search “nisley & your garment type”.

If you try the above and can’t figure it out, post the information on the garment you are interested in to this forum topic. Explain what you were able to figure out and at what point you couldn’t go any further.

Gunnar,

During three season conditions I understand that you will frequently hike in less than a 1 clo ensemble. The one clo ensemble is primarily used to calculate your total insulation after dunning a puffy layer for camp chores.

Gunnar,

You said, “The Iclo values given in Table 2 represents the possible Clo contribution of a layer of the insulation to the tolal Clo, if the whole body is covered by the insulation in a layer with the stated weight per sq-yd. This is on the condition that (a base ensamble is used beneath and) a boundary air layer with an air flow barrier is applied on top of it as required by the model. The other layers may or may not be part of the same garment as the insulation layer”

Correct

Latest minor edits to my pdf are found Here

Richard, somewhat related question.  Not tongue in cheek.  I’ve evolved from a competitive cyclist in my twenties, to a rounder guy in my late 30’s.  Does the fat layer ive accumulated on my upper body (went from Patagonia medium to L/XL) in jackets, actually keep me warmer now than when I was skinnier?

It seems so, but maybe that’s my biased perception.  Can people with higher BMI stay equally warm with less CLO in our layers?

Kevin,

Yes, because of both the thermal mass cooling down slower and because of more natural insulation.

Hi Richard,

I think I’ve got it now, by following along with one of your examples and doing one or two examples after that.

What about when the insulation in a jacket is down and they specify the total amount of fill, but not fill per sq meter or sq, yard?

Paul,

You said, “What about when the insulation in a jacket is down and they specify the total amount of fill, but not fill per sq meter or sq, yard?”

Insulation clo goes up or down based on the density. Synthetic insulation is always manufactured at the optimal density that provides the highest clo and is, by convention, reported in clo/oz.

Down insulation continues to increase in clo for up to 2.5x the density that just fills a baffle. For that reason, down insulation information is provided in oz of fill.

Here is an example to try and make things clearer. In the pdf’s Figure 7 I provided that 800 fill power (FP) down insulation Iclo for a Montbell Alpine Light Down Parka @ 5.24. Look at the Montbell specification for this garment and you will see that, in size M, it has 4.3 oz of fill. The majority of the garments used for UL backpacking have this construction and down FP. Let’s say you see a down hoody you are considering from brand X that has 1.8 oz of 800 FP fill. You simply multiply 1.8/4.3 * 5.24 = 2.19.

Let’s assume that another garment from brand X, you are considering, is a vest with a hood on it with 1.8 oz of 800 FP fill rather than a parka like the Montbell Alpine Light Down. The same insulation clo calculation applies to this unique garment; only the BSA calculation is unique. Per the pdf’s Figure 1, we know that rather than using a body surface area of 52% for a parka, this custom garment would use a body surface area (BSA) of a vest @ 36% and a hood @ 5% BSA for a combined BSA of 41%.

Once you determine the garment’s Iclo, then all of the other calculations are identical  to determine the camp chores thermo-neutral temperature and backpacking thermo-neutral temperature.

Paul, if you google the body surface area for an average male is 2,5 sq-yd. The insulation weight is normally given for size M, su it should match that body surface value pretty well.This gives:

(insulation weight per sq-yd) = (Insulation weight in jacket)/(body surface covered by jacket)

where

(body area covered by jacket) is:

0,52*2.5 = 1.3 for a hooded jacket

0.48*2.5 = 1.3 for a jacket without hood.

If someone has the approximate Clo (oz/sq-yd) for down as a function of fill factor, say in the range FF 500 – 1000, in a graph, it would be appreciated. I could not find it with google, and from the three values given by Richard it is clearly not proportional as I would have thought (so Clo 2Oz 500FF = Clo 1oz 1000FF) , not even linear. I then find it somewhat difficult  to make a good guess for other values than the ones given. (I am specially intrerested in the 1000 FF value.)

Having a hard time browsing on phone; do light baselayers (e.g. Patagonia cap 1 short sleeve) offer much value when sleeping?

for an unpicking trip im expecting a lot of exposure, mostly warm days (15-35c). But I am expecting Cooler nights, potentially dipping to freezing. So I’m going to use a looser fitting longer sleeve shirt for UV protection. I’m not so worried about “moisture management” on the go, and the long shirt I have dries faster than my Patagonia cap 1.

Assuming I kept my long sleeve dry, would the cap 1 have any benefit as a sleep layer (obviously cleanliness, but not worried about that for now)?

Not much other than keeping your sleeping bag/quilt clean.

Thanks brad.

Hi Richard,

Really interesting work you have here!  I’m a bit confused about some of the iclo values for down insulation that you have listed in Figure 7, making it quite difficult to estimate the iclo value of a different garment based on the fill weight.  Going back to your example comparison with the Montbell alpine light, if I take the ghost whisperer, which has 2.53 oz of 800 down, I multiply 2.53/4.3 * 5.24 = 3.08.  However in your table, you’ve tested the ghost whisperer to only have an iclo of 0.93.  If I do a similar comparison with the Golite Bitterroot, I multiply 5.3/4.3 * 5.24 = 6.46, but in your tests you list only 1.82.  Further, in your 2009 table, you list the iclo of the alpine light as 2.51 but in 2016 it measures 5.24.  And to even further complicate things, in Table 3, you list the iclo of the Montbell Mirage as 3.51 but in Figure 7 it jumps to 5.62?  My intent here is not to question the validity of your work, but to gain some additional insight on the best way to actually estimate iclo values on garments that you haven’t specifically tested.  Do these Montbell jackets just test way higher than everything else, making them poor pieces to base a comparison on?

Thanks for your help!

If the Capilene 4/Thermal weight is supposed to be a base layer what happens when it is layered over the thinnest and lightest of Patagonias base layers as so many people seem to do?

I have a fairly heavy PowerStretch top that seems to work better when layered over my Patagonia Everyday base layer or my Cap2 T-shirt

The math on page 7 of the PDF reads (.2028 + .1 + .74 = .9428.) That sums to 1.0428. Should a (-) sign be in front of the (.1)?

I love this document.

Does it assume that the Sun is not hitting the body? Does it assume anything about humidity?

Thank You

Just finding time to read this study. looks really useful. I did spot though the Cap 4 is described as being sewn from Power Dry. The curent version is made from Power Grid, a very different fabric. Posts on here seem to suggest it is warmer in still air but less so in a breeze.

Edward,

You said, “…the Capilene 4/Thermal weight is supposed to be a base layer what happens when it is layered over the thinnest and lightest of Patagonias base layers as so many people seem to do?”

The US Special Forces trains their people that this combination, regardless which is layered first, plus their Level 3 fleece and a shell, when active, is recommended to -20F. If that is what you have with you, it will work but it is not the most weight/warmth efficient layering.

Winter base layers are engineered primarily to move liquid moisture off of your skin, not provide insulation. Active insulation’s, like fleece, are designed to pass moisture in vapor form and are warmer for the same weight vs a base layer.

Matthew,

Thank you for your positive feedback.

I will correct the calculation error you pointed out.

The TN calc assumes no thermal radiation heating from the sun or a fire. It assumes 50% RH.