R values everywhere!

[Richard Nisley]

Frank Ramos said-"My experience is that Polarguard 3D, which is generally considered one of the more durable synthetics, loses from 30% to 40% of its loft after a month of use, and then loses no further loft thereafter."

"It is not clear which of the continuous fiber polyesters is best (polarguard 3D, polarguard delta, climashield, wiggy's lamilite). The reason it is not clear is because no one has ever studied the loss of loft among these insulations in a scientific fashion."

My experience matches Frank's regarding Polarguard’s initial rate loft reduction and then relative stabilization. In my case, this was a result of very tightly compressing Polarguard sleeping bags during an expedition.

I disagree with Frank's statement that no one has studied the loss of loft for insulation in a scientific fashion. The attached table is from a Natick Labs scientific study of the loss of loft for insulations. Polarguard clo value is reduced 11% as a result of the 40% reduction in loft that Frank experienced in the field.

In the case of Primaloft One, for the same loft destruction method, it does lose a higher percentage of loft than Polarguard. But… the resultant intrinsic clo value for Primaloft One is higher initially as well as after each destruction test than Polarguard.

In the case of down, there was a maximum of 8% reduction in loft for the highest loft destruction method versus 61% for Polarguard.

[Erin McKittrick]

Is there a way to get that data from the study for all the types of insulation? I'm getting ready to make a sleeping bag for a nine-month expedition, and would really like to know how much clo I can expect to lose from different insulation types before picking one.

[Dondo .]

Great stuff, Richard. I was thinking you might step in here.:-) Any data for Primaloft Sport? For any of the Climashields? Also, what specifically were the destruction methods? Thanks.

[Richard Nisley]

Erin-The research was designed to determine the clo reduction for the three classes of insulation used in sleeping bags. The clo loss characteristics for any sleeping bag insulation can be closely estimated by selecting the appropriate class.

I have done two Alaska expeditions. Each of them were kayaking and hiking for 1 1/2 months. The first was along the SC coast and the second was along the SE coast. For these types of environments, the down class of insulation is not optimal do to the constant rain. Either the synthetic continuous coarse fiber (Polarguard, Climashield, etc) class or the synthetic coarse/fine mix (Primaloft One, Primaloft Sport, Exceloft, etc) are fine.

If you tightly compress your synthetic quilt for pack storage, you can expect to loose about 40% of the coarse fiber loft or 50% of the coarse/fine fiber loft during your expedition. You will lose about 11% of the original coarse fiber clo value or about 40% of the coarse/fine fiber clo value. Since the coarse/fine class of insulation has an average 30% higher clo value to begin with, the end result is a wash between the two insulation types relative to clo loss.

I suggest Primaloft One (coarse/fine fiber mix) for your Alaska expedition. It has the least reduction in clo when wet (less than 10% versus about 40% for the continuous coarse fiber options). Design it with 40% more clo value than is needed when new. For the cold weather part of your journey, you may want to supplement it with a second quilt rather than having more warmth than is necessary for the warm weather portion.

[Richard Nisley]

Dondo – See my response to Erin to answer your first question.

Relative to the destruction methods:

-They quilted nylon taffeta fabric (MIL-C-21852 Type III) to either side of test insulation squares (24” per side which is the same size as a Guarded Hot Plate used to measure the clo value). The samples were channel quilted with 6” wide channels.
-They used three Armed Forces cleaning procedures: LADDS; DAFM 10-280, Formula II; Method 5556. The table shown below corresponds to Loft Destruction Methods 2-8. Item 1 was the original sample.
-They put one of two ballasts in with the test sample to continuously smash and contort the sample while it was being agitated or spun. They found that cotton cloth ballast was the most effective for destroying the insulation loft. The other ballast used was additional quilted insulation.
-They repeated each test a variable number of times. They used an average of three of the same sample types for each test.

[Franco Darioli]

One point that has not been made clear along with all the scientific jargon and theory is that once we have a "standard", for example the European copper man version, that is only a starting point. In other words you will only know if a 32F rated bag is any good for you once you have slept in it a few times at that given minimum temperature. At the same time having bags rated using a standard test it means that you could easily go from brand to brand or type (mummy/rectangular…) and expect the same outcome.
Franco

[Dondo .]

Thanks for the info, Richard. It's great to have you as a resource on this site.

[Dondo .]

Good point, Franco. I've been using a bag that's been EN13537 rated and find that the T-limit rating is just rignt for me. Others may be more comfortable with the T-Comfort rating or somewhere in between or higher or lower than either rating. But the point is, once you know where you stand in relation to the ratings, it makes it much easier to choose your next bag.

IMO, the Upper Limit and Extreme rating are absurd. You can always sleep half way out of your bag if you get too hot. And who would be crazy enough to try to sleep at the Extreme rating? Hikers who visit this site? Oh yeah, never mind.

[Erin McKittrick]

Thanks Richard. Just what I wanted to know

[David Wills]

It may be considered beating a dead horse, but cruising around the web i found several new additions to insulation available for sale. I made a table comparing all of them with wholesale prices accounted for if anyone is interested.

I ran across liteloft in my search and found it to have a clo/oz of .89, higher than all other insulations. I am familiar with its reputation of losing loft, but the 94% efficiency after 40% loft degredation mentioned earlier is pretty good. Seperatley, on one of wiggy's rantings, he noted that people got cold in liteloft bags and blamed it on loss of loft, but the product engineer for REI who he talked to insisted the publics perception of liteloft was bad, not the insulation. The research proves differently, and I suspect it could be manufacturers poor ratings to begin with that caused the coldness. I am a firm believer in clo as a measure of insulating capacity opposed to loft. Could liteloft still be a competitive or even superior insulation even if it is only available at dogbooties.com?

I always disliked horses either way.

[Arapiles .]

With relation to the comments about use in the field, because I am allergic to down (well, actually to the faeces of dust mites that live in down) I have always used synthetic sleeping bags. I have a Vango that is filled with Thermolite Micro (1.3 kg) that looks completely flat, probably because I used to heavily compress it – but I found that it was almost too warm at 0 C, and fine below that depending on what I am wearing. And having used it from new I haven't noticed any real loss in warmth.

Therefore I have always been puzzled by the obsession with loft as my experience is that it's not the be-all and end-all in relation to synthetics. Maybe it is with down, but I think synthetics are different.

[Dondo .]

>>Therefore I have always been puzzled by the obsession with loft as my experience is that it's not the be-all and end-all in relation to synthetics. Maybe it is with down, but I think synthetics are different.

Aripiles,
That has also been my experience with synthetics. Maybe the obsession with loft has something to do with the fact that warmth has at least some relation to loft. In addition, we all have access to rulers and can easily measure loft. Not too many of us have a copper manikin in the basement. ;-)

[Eric Blumensaadt]

We lose body heat in these ways:

1. CONVECTION > air currents carrying off heat

2. CONDUCTION > heat lost to objects like mattresses and even sleeping bag materials

3. EVAPORATION > heat lost to moisture (sweat) evaporating

4. RADIATION > infrared heat loss

We can conserve heat by limiting the WAYS we lose heat as well as the RATE we lose heat.

Some manufacturers have tried reflective layers to trap RADIANT heat. My old Caribou Polarguard bag has a "needle-punched" (to breath) mylar reflective layer.

EVAPORATIVE heat loss can be lessened by Vapor Barrier clothing or bag liners. These also slow conductive heat loss by keeping bag insulation dry.

CONDUCTIVE heat loss is slowed by good thermal barriers such as foam mattresses, and good, and dry, insulative bag fillings.
CONVECTIVE heat loss is best slowed by BOTH abundant BOUNDARY LAYER (1 or 2 molecule layer of "sticky" air next to insulative material, of which down has the most due to its great surface area) and by LOFT (thickness), which greatly slows air movement – i.e.convection – by "trapping" warm air. ALSO efficient bag design is hugely important. i.e. Mummy shape, efficient insulation stabilization, zipper baffles, and neck collars.

Combine the best technology and design in all these areas and you have the warmest sleep system.

Eric

[Richard Nisley]

David-Thanks for the table of insulation prices. Regarding your question, “Could liteloft still be a competitive or even superior insulation even if it is only available at dogbooties.com?”

The short answer is no. The long answer is that it is most similar to Polarguard Delta in insulation value when dry but much worse when wet:

• The Lite-Loft clo/oz value at .679 versus .68 for Polargaurd Delta
• For Equal weights of insulation submersed in room-temperature water for 20 minutes and excess water removed before weighing yields 500% for Polargaurd versus 995% for Liteloft
• The insulation value when wet drops drops to about half its original value for Polarguard and slightly less for Liteloft.

[David Wills]

That sounds how it should, but their website claims a clo of 2.5 for a 2.8 oz/sq yd piece of liteloft. thats where i figured the .89 clo/oz. is their site incorrect or am i figuring it wrong?

Thanks

[Aaron Sorensen]

I'm pretty sure those clo/oz are per ounce/yard.
.89 X 2.8 = 2.5

[Richard Nisley]

David-Your calculation is correct, but their published value doesn't match up with other independent tests.

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