winter closed cell pad advice

Joshua, I've been using a setup similar to what you propose in combination with a GG nightlight (below freezing) or thinlight (to freezing), but a ridgerest would probably work just fine as well. I happen to prefer the lighter weight of the GG products; if I recall, costs are similar.

Monty,
how bulky is a full length nightlight when it is rolled up? Equivalent to a ridgerest?

I was straying away from it because it seems to make a really fat roll on your pack, from pictures I have seen.

Have you ever used an ensolite pad (the classic blue foam pad, right?) in conjunction with this setup? I remember reading somewhere that they come in varying degrees of quality and insulation value, depending on the manufacturer.

I used a BPL TorsoLite + 3/8 inch thinlight + pack under my feet on the WT3 trip. We slept on light snow (we cleared most of it) and the temps reached the low teens. I was plenty warm with that setup in those conditions. I know some of the other guys used foam closer to 1/8 inch and I didn't hear any real complaints.

Joshua, I guess I was pretty spare in the info I provided, sorry. Here's more specific info:
* Thermarest ProLite 3 short, 13 oz.
* GG Nightlight 3/4, 3.3 0z (about 2" thick when folded. This is the "frame" for my pack).
* GG Thinlight full length, 1.75 oz (rolls up to about 2.5" dia).

Similar to what Chris says, for cold weather (mid twentys) I combine the two GG pads. For really cold weather I include the Prolite. No matter what the weather the pack always goes under my legs.

I haven't heard ensolite mentioned in ages! I don't think it's available anymore as it went by the wayside because it's so heavy, and it's not the same as the blue foam pad, which is lighter. I still have a 3/4 pad and it weighs 18.5 oz! A lot of folks swear by the blue foam as it's inexpensive, but I don't have any direct experience with it.

Ensolite — a blast from the past.

Ensolite was quite heavy, and the light colored version would become brittle and crack in temperatures of about 0 degrees F. There was a dark colored version that would remain flexible at lower temperatures, but it was even heavier, and hard to find.

Blue foam doesn't seem as durable or flexible as the GG foam products.

EVAZOTE is the best. Those are the YELLOW pads from Canada's Mountain Equiptment Co-Op (MEC)

http://www.mec.ca

Three thicknesses and sizes and weights:

a) BIVY (thin and shoort, nice for summer)

b) STANDARD (sorta normal sized)

c) WINTER (thicker and a little bigger)

For winter, the standard is appropriate, but the WINTER is a little bit nicer on snow!

Mike:

The Gossamer Gear pads are also Evazote…

Mike,
I got the ensolite pad terminology from your book! (birthday present, score!)

So when you guys say ensolite you mean evazote? And this is not the classic blue foamy? I have been laboring under a misapprehension, it seems.

So how do EVAZOTE pads stack up against a ridge rest?

Maybe way more information than you want (from the manufacturers websites):

ENSOLITE is a trademark for closed cell foam material made from a blend of Poly Vinyl Chloride and Nitrile Butadiene Rubber

EVAZOTE is a trademark for closed cell cross-linked ethylene copolymer foam

Anyway, I think the Evazote pads, at least as sold by GG, are more flexible than the Ridge Rest, and seem a bit more durable. To me, the blue foam pads (as found at Wal-Mart) are almost disposable in nature, and are a bit stiff.

Thanks John. this explains why a web search for ensolite only gives you hits on army surplus websites.

My ridgerest was a bulky beast for sure, and I have been pretty sceptical of those blue foamies.

Might have to pick up the MEC model. It's cheaper than a ridgerest, I think (I'm no good at currency conversion.)

ENSO-LITE is sort of a term that ends up like Klee-Nex.

I work at NOLS and we tend to call any ol' foam pad an ENSO-LITE. That's how it ended up in the book. No other reason.

And – Those MEC Yellow pads are awesome!

Well, I checked out MEC yellow pads.

MEC Zotefoams Evazote Winter Sleeping Pad
50 x 150 x 1.5cm
R-value: 2.06
Weight: 525g

RidgeRest
51 x 183 x 1.5cm
R-Value: 2.6
Weight: 400g

yellow pads seem to be the heavier and less warm then ridgerest.

John Whynot,
>Anyway, I think the Evazote pads, at least as sold by GG, are more flexible than the Ridge Rest, and seem a bit more durable.<

Just your assumption or have u used both GG and ridgerest?

From the reviews, GG nightlight do not seem to be very durable while I have never read a review stating durability problem with ridgerest.

I used the ivory coloured Ensolite pads to well below zero back in the '70s and they were Ok, but, not up to Evazote; they would sometimes crack, but, that was more likely at -20*F and colder and few go out in such cold.

I have Ridgerest, MEC orange Evazote, forerunner of current yellow, Z-rest, GG Torsolite and Canadian Tire Roots Evazote, I much prefer the GGTL and this Can. Tire slightly softer Evazote to any of the others. It IS a heavier pad, but, I am at the age where such is worth packing and it works so well in real cold that I favour it for any cold camping.

My take on it is that the MEC yellow pads FEEL warmer than Ridgerests, which I have four of and do not care for, each to his own.

NOLS, I used my Paul Petzoldt Expedition Bag with an Ensolite pad I made by using pink plastic surgical strapping to fit together three layers of 1/8" Ensolite. I often used this at -20 to -25*F and it actually worked just fine. The bag was warm, but, very bulky and heavy.

Hufeza:

Yes, used them both. I see what some of the reviews mean when referring to durability. I was referring more to abrasion resistance – I haven't noticed any loss of thickness yet.

I would like more info on where the R values come from.

>I would like more info on where the R values come from.

http://www.mec.ca/Products/product_detail.jsp?PRODUCT%3C%3Eprd_id=845524442094579
http://www.thermarest.com/product_detail.aspx?pID=49&cID=2

>I would like more info on where the R values come from.

Well, yes, vendors will post a number for R value, but is there a standard/organization/process that normalizes the R values for all of these materials?

Consider the situation with down – 800, 850, or 900 fill, depending on who and how it was measured.

Good question David.

Here is r-value from Wiki

"The R value or R-value is a measure of thermal resistance (K·m²/W) [1] used in the building and construction industry. The bigger the number, the better the building insulation's effectiveness[2]. R value is the reciprocal of U-value and one "R" is equal to ten tog.

Doubling the thickness of insulation will not double the R-value. An R-value only covers conducted heat, and is not a measure of the building insulation materials' qualities as a radiant barrier."

It would seem R value is only a partial measurement of
insulative value and only for certain applications.

Doubling the thickness doesn't double the R-value.

The manufacturer of Zote foams doesn't provide an R-value
so those figures must come from somewhere else.

Thanks for all the r value talk,very interesting

so, in a related question, do you guys (and gals, of course)lay your foam pads on top or underneath the air matress? I have always laid mine underneath, but I keep reading about people laying the foamy on top, something about air movement inside the thermarest. Is this a noticable difference? It seems like the short pad underneath would be uncomfortable and slippery.

David,
The article you referenced at http://en.wikipedia.org/wiki/R-value_(insulation) is not true relative to the statement, “Doubling the thickness of insulation will not double the R-value. An R-value only covers conducted heat, and is not a measure of the building insulation materials' qualities as a radiant barrier.”

The statement “…R-value only covers conducted heat..” is incorrect since it implies a limitation. R-value includes radiation and convection when they are present. My educated guess is that the person who wrote the Wiki article works for a radiant barrier insulation manufacturer and they edited the Wiki article for cloaked marketing hype. Alternatively they meant well but, copied the information from a radiant barrier vendor’s marketing hype without fully understanding the subject.

I have previously posted explanations of R Value to this forum. I explained that R-value is used to describe thermal insulating products includes heat being transferred by all three mechanisms — conduction, radiation, and convection. Since some BPL forum readers may think the Wiki has more credibility than I do, please reference the definitive scientific standard on this subject to see who is correct: The term used to rate insulation in the scientific thermal insulation community is “apparent thermal conductivity.” It is formally defined in the ASTM C168-97 (1997). Standard Terminology Relating to Thermal Insulating Materials, the American Society for Testing and Materials (ASTM) International, http://www.astm.org. R-value is just the reciprocal of apparent thermal conductivity.

I recently tested the R-value for the MEC Evasote Winter foam pad. They accurately represented the R-value. When I put two of them together, the R-value tested fractionally higher than 2x. This was caused by contact resistance between the two pads. In other words the foam pads are not perfectly flat and the small air gaps between two stacked pads adds to the total R-value provided by the pads themselves.

You said, “The manufacturer of Zote foams doesn't provide an R-value so those figures must come from somewhere else.” Zote foams publishes the W/m K value and the R-value is derived from it by factoring in the thickness. This now brings us back to the first point; the W/m K to R-value calculation clearly demonstrates that if you double the thickness you will double the R-value.

Thanks Richard for your clear explanation.

Well then, that means Ridgerest is superior to MEC yellow pads. Plus you can get them 3/4 lenght which weights a very cool 9oz!

And Ridgerest is heavier.

Thanks for sharing your expertise Richard.

I've been thinking about R values lately, particulary about combining different pads, because I'm interested in getting one of the new Thermarest Neoair pads when they come out next year, they are reported to be 2.5 inches thick, have an R value of 2.5, and be just 9oz (255g) for a 20×47" pad. I thought about backing one up with a thin closed cell foam pad in winter and wondered whether you could just add R values together to get the R value for the 2 pads combined.

Not knowing how R values are calculated my instinct was that you could not just add them. My thinking going something like this:

A 2cm pad may feel twice as warm as a 1cm pad, but a 20cm pad will not feel twice as warm as a 10cm pad.

But it's likely just a case of misinterpreting what R values mean.

If heat transfered halves when R value doubles, then it's just that above a certain R value, the rate of heat loss that's being halved is very small and so the difference is not noticable. In other words there are diminishing returns as the mat gets thicker.

The R value, and hence thickness of mat, at which further increases in R are not noticable will vary with temperature, and person to person of course, but we should be able to come up with a rule of thumb for the required minimum R value at a certain ground temperature.

Alternatively a function to work out equivalent R values in terms of comfort level at different ground temperatures. I.e. if I know that I personally am comfortable with a mat of R value 2 when the ground temperature is 15C, what R value do I need for my winter trip with ground temperature -5C?

Andy.