I see conflicting information on Climashield insulation values between thru-hiker.com and a BPL article ("Statement on Sleeping Bag Temperature Ratings").

I want to make a 2-person quilt for a mid-September AT hike along the Virginia Blue Ridge mountains. I think the low temperatures should be above 50 degrees F (comments are welcome on this). My RayWay 2-person quilt is too warm by 20 degrees (about 1.8" loft), so I'd like to make a lighter version.

What thickness Climashield should I use for 50 degrees F, assuming the quilt provides all the insulation?

Thru-Hiker lists 2.5 oz at 0.6" loft and rates it to about 40 degrees F. But the BPL article lists 1.2" as the required thickness for 50 degrees F. My experience with the RayWay quilt is that 1.8" is about right for 30 degrees, which agrees with the BPL article.

So, what's up with 0.6" loft for 50 degrees at Thru-Hiker when the BPL article says 1.2" is required? And 1.2" would require 5.0 oz Climashield, which seems excessive (Thru-Hiker says 5.0 oz is good to 20 degrees F).

These are big differences...please enlighten me...




Note: OWF seems the cheapest by far if you buy 20 yards of fabric (in my case, 1.1 oz seconds), and then they sell you the Climashield at "wholesale" prices, way cheaper than Thru-Hiker. I plan to make some vests and other items along with the 2-person quilt. Saving an ounce or two on the quilt is not worth over double the price, at least to me.

Edited by ewolin on 02/22/2008 19:58:30 MST.

This topic has been debated in length on these forums. Climashield loft does not correspond to down loft in terms of warmth. If you search for climashield im sure something will come up.

Edited by jegsmith on 02/22/2008 20:10:50 MST.

Elliott,

That BPL article was written by a few folks that really didn't know what they were talking about. They thought you could rate a synthetic insulation like you rate Down. Trying to imply that you need the same inches of LOFT for the synthetic insulation as you would if you were using Down.

Don't get trapped into thinking that just because you read it at BPL that it is true or correct. It might have been true way back then - but the world has moved on.

Most of the old articles that were so good when they were written are now so out of date that they are long over-due to be revised or dumped.

Todays newest synthetic insulation is so much better than anything that has ever been available.

For the MYOG person and picking from synthetic insulation that is easy to get, easy to work with and that you can buy - by the yard, you only really have two to pick from.

Climashield Combat or Climashield XP.

You can use the table from the article for a theoretical value to use as a guide. Inches of loft for Down is a good number to use when seeking the amount of synthetic insulation. To get a guide to the amount of synthetic you look at the CLO value of the insulation. As an example if for down the table says you need 1.5 inches of loft for 50 degrees then you take that number 1.5 and transpose it to the CLO value of the synthetic you are looking at.

As an example Climashield Combat at a CLO of .78 and using a piece rated at 2 ounce per sq yard you get a CLO of 1.52. That is the CLO of .78 times the 2 ounces. The 2 ounces is the weight of the insulation on you. If you use 2 layers then it would be 4 times the CLO, etc. All things being equal that one layer of 2 ounce per sq yard of Climashield Combat should keep you as warm as something made out of down with a 1.5 inch loft.

You will not get those selling synthetic insulation to tell you that as they fault on the conservative side of how warm your item might keep you.

The inches of down loft vs the Clo numbers are a guide. How you make you quilt / sleeping (design) is part of the finial determining factor. The material you use is also very important.

Edited by bfornshell on 02/22/2008 20:58:03 MST.

Elliot,

50F requires ~ 3.88 avg. clo per the EN 13537 standard. Note that this is for the average 30 yr old male, wearing long underwear, and using a pad with insulation equivalent to a Thermarest Standard model. This also includes the hood or hat(s) insulation value. A spooning couple will reduce the insulation requirement by half.

Climashield XP has an insulation value of ~.82/clo oz. So, one layer of Climashield XP 4.5 oz (1") provides 3.69 clo and one layer of Climashield XP 5.5 oz (1.3") provides 4.51 clo.

Climashield XP has a high insulation value, in part, do to its mix of thick and thin fibers. Repeated stuffing and washing will degrade its insulation value quicker than the all thick fibers used in Polarguard 3D (older Ray Way quilts). Assuming you are not spooning, I suggest the single layer 5.5 oz option to provide the longest life for your application.

Edited by richard295 on 02/23/2008 07:13:04 MST.

In addition to the relative warmth of any type of insulation (down or any synthetic) the shell fabric is also very important. A looser weave, no or poor dwr or a lack of proper calendaring in the fabric will allow warmth to move through the inside and outside shell quicker.

I can tell a lot of difference when I proto a quilt with a generic 1.1 nylon and high quality Momentum.

I've tried thinner and lighter 20d and 15d shell fabrics and while the entire amount of fabric in the shell may weight 10% less, or about .5 - 1oz for the entire quilt, the thermal efficiency loss would need many times that weight in insulation to regain the loss.

So, I offer than even a slightly lower clo of insulation, maybe less important than a good shell fabric for pure warmth.

I have not tested any of the very newest 15d or 7d fabrics as offered in the latest Montbell clothing items, but wonder if they move past the thermal efficiency gain equation.

Also note that there are a lot of factors in the weight and effectiveness of a fabric other than the denier and that a quality 15d fabric is not 25% lighter than a quality 20d, etc. (If that were the case, a 7d fabric would weigh less than .25 oz sq/yd!)

This idea also goes for bivy tops. A high quality top fabric will be warmer than a generic one.

Well I've read just about every post I could find on CLO and temperature ratings, and scoured the web to boot, and I've found no definitive relationship between CLO and temperature rating. The reason is that that there are so many intangible factors, including: bag/quilt construction; age/sex/condition of occupant; sleeping style (roll off your pad and kick your quilt out the door vs still as a corpse; ambient conditions; insulation age/condition; warm/cold sleeper; etc.

In summary, there seems to be two schools of thought that differ by about a factor of two in temperature rating vs CLO. One tends to agree with the BPL statement and the European standard (EN 13537). This standard actually gives a range of temperatures vs CLO, from survival, to healthy male with additional clothing, to healthy female sleeping soundly all night. The BPL table temperatures are slightly lower than the EN 13537 standard for a healthy female. The BPL table also agrees with my experience with down and synthetics.

The other school agrees with Thru-Hiker recommendations, and generally claims about one half as much CLO is needed for the same temperature, although they assume more you wear more clothing to bed, I think. Thru-Hiker says that EN 13537 is very conservative and accounts for insulation degradation and loss of loft over time, amongst other things.

What to do? Since my wife and I both easily get chilled (sign of age!), and she sleeps colder than I do (I often leave a leg and/or arm outside our quilt while she is all huddled up underneath), I will opt for the EN/BPL ratings, and leave the Thru-Hiker ratings for those hardy souls who sleep cooler than me.

Thus I'll aim for a CLO of around 4 for 50 degrees F (as recommended by Richard N), allowing for eventual insulation degradation, and leaving a margin of safety.

Note on CLO values for down (someone please verify): the 3M site lists a square yard of 1.1 inch of 550 fill power down at 4.88 CLO. 1.1 inch x (36 inch x 36 inch) gives 1426 cubic inches, and takes 1426/550 = 2.6 oz of 550 in**3/oz down.

Thus if the 3M site is correct down gives 4.88 CLO / 2.6 oz = 1.88 CLO/oz. Most synthetics have less than half this CLO/oz, and 800 FP down would even be better.

Edited by ewolin on 02/26/2008 13:13:11 MST.

> The reason is that that there are so many intangible factors,
Only partly true. The factors are there, certainly, but there are also basics like metabolic rate. OK, people vary, and you do need to know where you fit into the scale of things.

> Thru-Hiker says that EN 13537 is very conservative and accounts for insulation degradation and loss of loft over time, amongst other things.
From my reading of the EN standard and associated literature, I cannot see anywhere that the Standard tries to allow for the future degradation. It measures what is NOW, and does so in a reproducible and standardised manner. Unlike some other dodgy claims.

You have quite a bit of info at your fingertips already .... but probably don't really know it.

What is your Rayway quilt made of? Polarguard 3D or Climashield?

Once you know what material you have already used then all you need to know is what the current CLO of what you have is. Then you can relate your personal experience with your 30 degree quilt to your current clo rating instead of loft.

If you're using a 3D quilt, like I was, then you'll find that that material had a CLO of around .63 and a weight of something like 2.7 ounces per square yard for the standard 30 degree quilt. This quilt was good to 40 degrees for me, so the temp was right on.

Two layers at 2.7 oz per layer, or 5.4 ounce, times .63, yields a clo of about 3.4. Therefore, for me, a 40 degrees was a clo of about 3.4.

I extrapolated from there.

One other note on temperature ratings ..... what are the other conditions outside?

Are you in a tent? Are you in the wind? Is there really high humidity? Do you have a good enough pad under you?
Do you have a good groundcloth?

All these factors, and more, can have an effect on temp rating. A mistake that many people make, myself included, is to expect a 30 degree bag, or quilt, to always keep you warm at 30 degrees.

If you're not well hydrated, well fed, too little insulation, sleeping under the stars in heavy dew, in the wind, etc .... you're not going to be warm at 30 degrees.

I'd like to take a minute and clarify what Eliot and I discussed over the phone.

I believe EN 13537 is a conservative standard but it's as good a place to start as any. For those with an EN 13537 rated bag, it would be easy enough to calibrate one's own insulation needs through field testing of a bag and then deciding where in the spectrum you fall. I'd like to hear from folks who have been able to sleep in EN 13537 rated bags having not tried one myself; I don't think the US has adopted the european standard. If we haven't, I vote we adopt both it and the metric system at the same time ;)

I also said that I believed Mr. Nisley's reasonable recommendation was conservative and probably accounted for steady state performance, that is to say his recommendation assumed some loss of loft ("I suggest the single layer 5.5 oz option to provide the longest life for your application").

On the other hand, I don't think you'd have to go far here at BPL to find someone that can make a 2.5 oz XP item go down to 50 degrees. Is this the 'frozen female' or 'lower limit' choice on EN 13537?

The way I look at this is that most folks who aren't experienced enough to know about clo and how much insulation they need will buy it by inches of loft. This will give them an amount of insulation more or less equal to a 'for sure' conservative rating. The experienced folks are free to make their own decision based on clo values. Eliot and I discussed his prospective project from the standpoint of his previous 2 person ray-way 3D quilt for this reason. When you look at what he says about it ("too warm by 20 degrees", "want something lighter",1.8 inches-3.8 clo-6 oz 3D loft) I think it's hard to say that a 5.5 oz recommendation of XP is going to fit the bill.

Roger, give me a call sometime. I think if you and I spoke over the phone about insulation you'd find me to be a pretty reasonable guy not prone to making dodgy claims.

AYCE

Edited by PaulNanian on 02/27/2008 07:32:17 MST.

I'll admit I sleep a warm, but with silk pjs and a fleece hat my lower comfort on my 2.5 xp topbag is 40*. Before, when it was a quilt, i would say about 45*. For me, 5.5 oz insulation would have me burning up anywhere above 40*. I definitely use the approximations on Ayce's website and adjust them to me before I would consider the outdated table on BPL. For my hiking style though, I would consider a base weight of 3.5-3.7 oz of some sort of climashield (depending on vendor) for your uses.

Edited by willspower3 on 02/26/2008 21:37:21 MST.

Integral Designs synthetic sleeping bags use the following.

Insulation: Primaloft Sport, clo/oz = 0.74

Temp   Insulation   clo
------------------------------------
50 F       3 oz       2.2
40 F       4 oz       3.0
20 F       6 oz       4.4

Based on the above, 30 F should require 5 oz, clo = 3.7 .According to the European EN 13537 standard, this clo is only comfortable to the low 50's ! So there is indeed a vast discrepancy. Perhaps Canadians are tougher?

Edited by chris_jackson on 02/27/2008 00:13:39 MST.

This would not be directly relatable to quilts, but heres how phd in the UK relates down fill wt with minimum temperature rating for a sleeping bag..

An important caveat...earlier I calculate 1.88 CLO/oz for 550 fill power down, based on something on the 3M site. But I used the unrealistic figure of 550 cubic inches per oz of 550 FP down, true in some sort of laboratory test, but likely not in a real sleeping bag or quilt. I can imagine an ounce of down fills up as little as half of the laboratory rating in a real bag.

Anyone know how many cubic inches per oz of 550 FP down (or other fill powers) one can get under real conditions?

Edited by ewolin on 02/28/2008 07:15:48 MST.

Elliot,

You asked, "Anyone know how many cubic inches per oz of 550 FP down (or other fill powers) one can get under real conditions?" The answer is that it averages 484.3 FP under real world conditions.

Thanks, Richard.

484.3/550 = 0.88, so under real conditions down (I assume quality down and good construction) yields 88% of the loft rating. I assume this is roughly true for all down types, from 550 FP through 800 FP.

So my modified CLO/oz for down is 1.88 * 0.88 = 1.65 CLO/oz of 550 FP down. For 800 FP I get 800/550 * 1.65 = 2.40 CLO/oz.

Not bad compared to around 0.8 CLO/oz for Climashield and similar synthetics (and assuming I haven't made any mistakes).

Elliot,
I dont have figures but my guess is that very light down 800FP will on average collapse more under imperfect conditions than heavier stiffer? 500FP. The lab tests are in dry conditions with no outer cover. The weight and volume of the outer cover have a lot of effect. A sheet of pertex Quantum floated over a tub of down will allow more loft then a heavier fabric. I think you are guessing in the right area but take account of the weight of the envelope.

Elliot-

I don't know how you came up with your numbers for the clo value of down using the values given on the 3M chart you cite (I assume it's this one: http://solutions.3m.com/wps/portal/3M/en_US/ThinsulateInsulation/Insulation/Thinsulate-Products/Thinsulate-Lite-Loft-Insulation/).

These numbers you've calculated ( 1.88 * 0.88 = 1.65 CLO/oz of 550 FP down. For 800 FP I get 800/550 * 1.65 = 2.40 CLO/oz) are off by a factor of 2 to 3 times.

That chart lists the total clo for a 7.0 oz/sq yd layer at 4.8. This means that a normalized clo value of 4.8/7.0=0.69. Doesn't this value make a lot more sense than that 550 fill down is two to three times as efficient as the synthetics?

Derek - You said, "I don’t have figures but my guess is that very light down 800FP will on average collapse more under imperfect conditions than heavier stiffer? 500FP". The higher the down’s fill power, the larger the percentage of three dimensional plumes. The air trapped by those three dimensional plumes and the radiation absorbed by them is what provides the insulation warmth. Lower fill powers have a lower percentage of three dimensional plumes and a higher percentage of two dimensional elements which includes plume branches that are broken off, feathers, dust, etc. The two dimensional elements don't contribute any thing to prevent loft reduction under imperfect conditions.

Paul aka Ayce-You are correct in your derived clo/oz for 550 down. My test results show an average of .702 clo/oz. For practical purposes this is the same as your derived value. I didn't go through Elliot's or your calculations, I just looked at your derived clo/oz number.

Edited by richard295 on 02/28/2008 15:25:45 MST.

On a 3M site I found a statement that 1.1 inches of 550 FP down gives 4.88 CLO. Everything I worked out is based on that. I have no clue where it came from, nor if it is correct.

I didn't see anything about down weights, so I worked backwards to get it. If Paul's info is correct, and I didn't make any arithmetical errors, then the original info I used was incorrect or misleading.

I'll admit I was surprised at the down CLO results I calculated, as they seemed too good to be true (which is why I posted them for comment...which worked, thanks to Paul!).

I'll have a look at Paul's reference tonight and try to figure out what's going on...

Paul,

3M is being disingenuous with that chart. Earlier versions on the web used to state that the down weight basis included a 1 oz scrim (or something like that) on each side to contain the down. That fine print is now missing. This trick is how they claim their synthetic is more weight efficient than down; something no serious user of back country insulation would believe from experience.

So they are adding the weight that a garment or bag would have for their down values, and then not using those fabric weights in their synthetic stack ups, creating a deceptive comparison as no one wears synthetic batting by itself.

A 1.1 ounce thick square yard batt of 1.1 oz nylon/ 488 in^3/oz effective fill down / 1.1 ounce nylon would weigh only 1.1 + 1.1 + 1.1 in *(1296 in^2/yd^2)/488in^3/oz = 5.12 ounces/yd^2, not the 7 ounces they claim. So the effective clo of the down garment is somewhere around 0.94 Clo per ounce or about 4.3 Clo per inch (typical for loose fill insulations which are close to 4 clo per inch of dead air space). However since their basis weights are dubious, I would question their clo measurments as well.

So the quoted 3M values for synthetics in Clo per ounce don't include the shell and liner weight as for down. Different grades of fill vary some from the average of about 4 clo per inch or about 0.8 clo per ounce (per square yard, a density that still relates clo to thickness anyway). Down has variable fineness to the fiber plumules, which is why it has a high clo per inch. It's density being about half of the best synthetic gives it a higher clo per ounce.

Clo is useful for comparing synthetics when new, but no one publishes clo/oz degradation from loss of loft with use. For garments this isn't a big issue as a hikers metabolic output makes garment's design less critical, and garment tuning via layering and ventillation is an option that sleepers don't have without waking up.

In my experience for sleeping bags (actually a quilt), your 800 fill down IS 1.5 to 2 times as efficent as synthetics. This assumes proper design and filling to get an effective fill power around 600+ in^3 per ounce. The best synthetics do when new is around 400 in^3 per ounce and that degrades quickly with stuffing. On top of that with age I can open up a down quilt or bag and boost its fill with a few ounces, whereas my synthetic creations get downgraded in temperature resistance with every season of use, or they are overbuilt to break in to a final thickness.

I would say that whatever small variations in clo the various insulations deliver is a minimal benefit compared to design elements like baffles and collars. Over 20 years of building weight efficiency has largely come from lighter shell materials and better cut patterns. Down and synthetics are pretty close for garments and bags for above freezing, but for high loft, high fill uses, the efficiency of down really starts to add up.