Minimum R-value for sleeping on snow, in summer

[Paul S]

Curious about what R-values people feel they need for camping on snow leftover from winter during their spring/early summer trips? Assume night time air temps of 40 degrees or so.

 

Thanks!

P.

[Paul S]

And, of course, I am referring to sleeping pads here.

 

[Jon Fong / Flat Cat Gear]

I use a NeoAir (original): it probably has an R value of 4 or less.

[Bill Budney]

R4 for freezing, R6+ for 0F/-18C.

[Steve S]

Snow is an insulator that warms to 32F in any season/temperature, Thus the same pads work equally well or poorly in any season, apart from heat loss other than from below.

I’m speaking from both theory and practice.

[Bruce Tolley]

I always try to sleep in places where the snow is not. The snow will suck heat out of your body through conduction.

[Steve S]

I think I ought to elaborate on my previous comment, since Bruce posted a comment that disputes both my facts — conductivity of snow — and the implications for comfortable sleep.

I prefer sleeping on snow, since conduction is minimal and my tent or bivy bag bottom sees no wear or tear. One can also flatten the sleeping platform when on snow, but that is separate matter.

As I said in my earlier post, the influence of temperature on snow when sleeping is a constant. Rock surfaces below freezing suck heat; whereas the toastiest duff or vegetated surfaces below freezing are still colder than snow due to conduction. The reason is that conduction causes surfaces below freezing to stay below freezing all night or for a long period, rather than warm to freezing quickly as snow does. So in deep winter less protection from cold ground is needed than from snow of any temperature.

I started my winter travel in the Northeast, but most of my life I’ve been in Oregon. In most of the areas I prefer in the Pacific Northwest the snow travel season is 8 months long, as a norm. (I’ve ski toured on the current year’s snow in every month of the year — different years for September and August.) Avoiding snow is possible in late spring, but not earlier. So I have much practice behind my comments.

[Bruce Tolley]

Steve, I do not think we are disputing. I was stating my experience/practice within the parameters stated by the OP. “…spring/early summer trips…  Assume night time air temps of 40 degrees or so.” So ambient air never drops below freezing.  I would choose not to sleep on snow. If I absolutely had to sleep on snow in early summer, I would use my rectangular original NeoAir, and if I got cold maybe also put my pack underneath. But usually there is a somewhere melted out and dry to camp on.

[Paul McLaughlin]

For me, my original Neoair is NOT warm enough for use on snow. I’d want some closed cell underneath it to make that work. 1/4″ would probably do it. But – I find that in late spring/early summer even in areas where there is still a couple feet of snow left covering the general area, it is rare to have complete enough coverage so that you can’t find some bare ground to camp on if you want it. Talking Sierra Nevada conditions.

[jscott]

I’ve often been camping early season in areas with a lot of snow, and a few dry areas. I always opted for dry ground, although Steve makes me question that. Still with temps falling below freezing and a good bag, using an Exped rated at 3, I was always warm. And I sleep cold. Thinking about it now, I’m a bit surprised! I use it with a GG thinlite foam pad for puncture protection, but that adds little R value.

In the Spring I’d bring my bag rated to 15%. Marmot Helium. That would be overkill in temps at night in the 40s.

[Bruce Tolley]

@ Jscott, I think Steve is referring to winter conditions where here in Pacific West at least the surface of the snow rarely drops below 32 degrees.  So the snow can insulate the human from earth or rock under the snow which might possibly be colder than 32 degrees. This is why snow caves and snow shelters that are properly built can be quite cozy in winter when the ambient air temperatures drop into the 20s if not the 10s in the Pacific West.

But the OP was asking about spring, early summer where the nighttime ambient temp dropped to 40 degrees. (BTW If the nighttime low is 40 I would think the daytime high is at least 70. ) I am a tarp camper and often just use my bivy, and in those conditions below treeline, I look for a snowless site where the afternoon sun has warmed the earth, preferably next to a big tree which will radiate some heat out at night.

And to Paul’s comment, yes I would not be comfortable just with the NeoAir, but I think with my pack and perhaps a Gossamer Gear thinlite I would be Ok.

[nunatak]

With snow, summer or winter, I really prefer to have a closed cell component somewhere in the mix. In fact, if I could bring only one pad on snow it would be a ½” CCF, even if it theoretically only rates at 2.0 or thereabouts.

 

[Bruce Tolley]

Excellent point about CCF.  Mountain Laurel Designs and Gossamer Gear and others sell 1/8 and 1/4 inch CCF.   1/2 inch CCF (4/10 by my calculation) is available here at a reasonable price: https://nunatakusa.com/supplies

[Paul S]

This weekend we slept on snow. X_lite pads, with z-lite underneath.

When we inflated our pads the air temp was about 45 degrees F. It cooled down to 34 deg F in the wee hours of the morning. We both had a slight chill coming from underneath because the air in the pads contracted, which made the pad softer, and thinner. Slight chill from beneath! My wife used her Womens X-lite (they no longer make it, it has a R value of 5.4). She has used it in winter and been fine. I think that in the winter, when we inflate our pads (and we only use the pump sack, and DO NOT blow our warm breath into it)  the pad gets inflated with air that is already close to the night time min temperature, and so that pads do not contract much at night. But in summer, on a cold-ish night, camping on leftover snow from winter (very dense and wet snow), the pads contracted and we were less than completely warm. Of course, all we needed to do, to solve this nuisance, was add a little more air to our pads. But in that half-sleep state, where you don’t want to have to do anything about anything, we just waited till morning, toughed it out.then…hot drinks, hot cereal, warm sunshine!  :-)

 

I think a lot of the funny business with air pads is the physics->when air cools it reduces in volume. I have a suspicion that many negative reviews of air pads can be attributed to this.

[john mcalpine]

This is a timely subject.   I just returned from two nights on the snow.   The temperature never dropped below 40.   Things are melting here in the PNW.

I slept on the Nemo Tensor Insulated at R-value of 4.3.   I used a new 25 degree Zen-bivy bed ….so a quilt.

I sleep on my back and both nights my back was cold.  I’d roll on my side and my side would get cold.  I made sure the pad was completely full.

Next time I’ll bring my Z-lite to add an additional R-2 for a total of 6.3.

 

[Jerry Adams]

The few times I’ve slept on snow I’ve used an extra CCF pad underneath my air pad.  Thermarest Ridgerest.  I think one of the warmer air pads would provide enough warmth without the CCF.

When camping on snow, the bottom surface against the snow will be 32 F

When camping on dirt, the bottom surface will warm up to maybe 50F.  It depends on the material you’re sleeping on.  Thus, you need less insulation between you and that 50F surface.  The dirt on the ground provides some insulation.

I really try to avoid camping on snow because it’s so cold.

[Paul S]

Here in WA state, in the Cascades Mtns, we are often camping on snow until sometime in July, with lots of snow on the ground usually in late October or early November. S0, 9 months/year camping on the snow!

[Author]

Posts