I'm looking to lighten up my sleep pad and was looking at the Gossamer Gear ThinLight insulation pad. Comfort is not an issue, but warmth is. Does anyone know the R-value of these pads? They come in 1/8", 3/8", and 1/4" thickness. I'm curious on the R-value for each, but I am thinking seriously about purchasing the 1/8" pad.

At 2 ounces it should insulate most of my body (19.5"x59") and I'll use my jacket as a pillow. The price is right too ($9.00).

3/8" = ~1.36
1/4" = ~.90
1/8" = ~.45

Edited by richard295 on 12/29/2006 11:07:10 MST.

Richard's values seem reasonable. For reference, I have slept on top of snow, in a Sleeplight bag, with just a polycryo ground cloth and a 1/8" thinlight under my legs (Nightlight Torso under my torso), and found that it was fine.

Does anyone know the R value for 3/8 in. blue foam pads? Richard?

Zote Foams Evazote EV45CN (typical material used in backpacking sleep pads) has a thermal conductivity of .038 W/mK which gives it an R-value of R-3.8 per inch. This agrees with Richard's numbers to within about 10 percent. I expect blue foam pads to be pretty close to this, giving similar values for the same thickness.

To contrast Glen "Icicle" Van Peski's experience, I like at least R-3 under me for sleeping on snow. ;-)

Glen, Ryan, and some hardcore others seem to be able to get away with much less, so experiment to see what works for you.

Cheers,

-Mike

Edited by MikeMartin on 12/29/2006 11:17:20 MST.

Blue foam is not as durable as GG's Evazote® nor as warm for a given thickness. Although all blue foam looks much the same, its quality varies widely. Squeeze the foam between your thumb and forefinger. Inferior foam will spring back slowly, if at all. The best available blue foam has 9% EVA content. The smaller the W/m K number, the more insulating the pad is. The average thermal conductivity, for the best blue foam, is .040 W/m K, whereas GG's Evazote is, depending on the sample, .038 - .039 W/m K.

As Mike said, the two types of pads 3/8” R-value’s are similar. The best 3/8" blue foam pad's R-value is 1.35. Using Mike’s .038 W/m K for GG Evazote yields a 3/8” R-value of 1.42 for GG’s Evazote.

Edited by richard295 on 12/29/2006 12:47:09 MST.

Thank you, gentlemen. Very helpful.

Just as Glen stated, I'll just be using the 1/8" foam for under my legs (and maybe my arms). I'm using a Insul Mat Uber Micro for my torso. About the same weight as the NightLight Torso (Insul Mat is 3 1/2 oz) but not as thick (1 cm for the Insul Mat). With an R-3 rating for the Insul Mat I probably only need the 1/8" ThinLight just to knock the chill off from the ground.

Thanks for everyone's help. This has been the place to come to get my questions answered.



>>I have slept on top of snow, in a Sleeplight bag, with just a polycryo ground cloth and a 1/8" thinlight under my legs (Nightlight Torso under my torso), and found that it was fine.

Glen, as skinny as you are, how do you keep from turning into a popsicle?

> I am thinking seriously about purchasing the 1/8" pad.


I have used the GG ThinLight 1/8" pad with a quilt on the ground and in a hammock down to about +40F and found it warm enough. I usually add a torso pad for comfort, but I haven't noticed being cold where the only insulation between my bare legs and the ground was the GG ThinLight 1/8" and a polycryo ground sheet. YMMV, and I can't comment on its effectiveness alone on snow or below-freezing ground temps.

Edited by Otter on 12/29/2006 15:20:33 MST.

Doug,

If like these GG pads and if you want to push your quilt lower and eliminate any drafts check out the Down to Earth Pad Converter in the Spotlites.

Pan

>If like these GG pads and if you want to push your quilt lower and eliminate any drafts check out the Down to Earth Pad Converter in the Spotlites.


I am definitely considering that solution. I have been using my Jacks R Better Nest quilt for ground sleeping this year, and it's just a bit freezy when I roll over in the night (my chest/arm girth is 60") with a nice breeze blowing through my tarptent or cape. I was going to mod my Nest with the JRB Quilt Wings, but I may go with the Pad Converter instead since I always use a GG ThinLight anyway. The only extra weight is a bit of OmniTape, and the cut-down GG ThinLight pad would probably make up for most of that.

Edited by Otter on 12/29/2006 17:03:16 MST.

Doug,

Figure the assembled girth at 64 inces... so you it should fit nicely for you... The mod to your No Sniveller will add right at 1 oz; and the omni tape on the pad is a net plus of about 0.4 oz over a stock 1/8 thin light... the shaped 1/4 pads are below the stock weight even with the OT.

It is a significant plus up in warmth as there is no heat loss above the pad on body shifts as it is totally wrapped by the quilt....

Down side is you roll inside the "Bag" not with the "Bag"...no big deal for most, an easily learned and mastered technique.

Pan

>>Glen, as skinny as you are, how do you keep from turning into a popsicle?


I have low expectations ;)

The 1/8" GG pad was one of my first investments in "UL" gear. Just to be safe I also bought the thicker pad at the same time, I think 3/8" a few short months ago.

The 1/8" has done it for me, in all circumstances above 40 F temps and even in snow conditions that were "mild." Keeps my lower legs protected and warm and doesn't weigh anything to speak of, like 1 oz.

And, it reaches far enough that I not only use it as a vapor barrier and leg base, but it extends just up over the end of the torso pad far enough to serve as a base for a UL inflated light weight pillow at a fraction of an ounce. So, I would highly recommend experimenting with the 1/;8" to find out what fits you. I love it.


So the thermal R values are new to me, but it works in snow if you have your sleeping gear together and the accomodations ... so I think it is an operator controlled outcome whether the 1/8 " works for you.

Edited by bdavis on 12/30/2006 01:09:52 MST.