Forum Index » GEAR » Insulative value of sleep system??


Display Avatars Sort By:
Jeremy Gustafson
(gustafsj) - MLife

Locale: Minneapolis
Insulative value of sleep system?? on 02/12/2010 07:18:16 MST Print View

I am headed out for a winter camping trip in Northern Minnesota and am trying to figure out how cold my planned sleeping system will take me.

It is currently -18F in the region that we are headed too. We are not going until the end of Feb., but it could still get that cold or colder at that time.

Can somebody give me some good feedback on my numbers and questions??

Referencing Mark Verber's website for insulation values and playing it conservatively...

- Sierra Sniveller Long - 2" Baffles with 2.5" Overstuff -> WM says 20F for 2.5", JRB says 25-30F)

- Lafuma 45F Polyfill Bag (Long) converted to quilt (overbag) - 1" Loft for a total of 3-3.5" -> Verber says 0F for 3.5" (I would probably put the system at 10F)

- Titanium Goat Raven XL Bivy - Verber says 5-15F addition. Due to highly breathable material and non-reflective, I put it closer to 5F Addition (Summing it up, the system so far should get me down to 5F)

- Insulated clothes - Marmot Down Inner Jacket has about 2" loft, BPL Cocoon Pro 60 Side Zip pants are about 1.5". In theory, this should get me down to at least -30F, but I'd be surprised if this was actually the case. I'd also be extremely nervous about pushing it that cold!

I plan on wearing my VB socks in my wool boot liners for my feet. I also have a poly-fill insulated balaclava for my head. Lastly, I will be wearing all my base layers (merino wool).

-Sleeping Pad -> REI Blue Foam 3/8" = 1.4 R-Value, I'm pretty sure the Walmart Pad I just picked up is 1/2" which has a 2.2 R-Value. I'm not actually sure how cold this will get me too, but I would think easily down to 0F. Haven't totally figured this out yet.

Questions:

Will each layer allow the layer below it to loft fully?? I guess this is one advantage of using quilts, however, the bivy will only allow so much loft as well. I plan on putting my sleeping pads outside of the bivy, so this should help.

Also, I have thought about picking up a down vest to combine with my JRB down sleeves in lieu of bringing the Marmot Down Jacket. Is this worth the weight savings?

Because I have the Sniveler, I can wear that as needed around camp if I decide to swap out the down inner with a vest. Or am I risking too much using my down quilt out in the elements?

I plan on using a Driducks XXL jacket over either my down inner or over the Sniveler quilt. Any thoughts on this?

Chris W
(simplespirit) - MLife

Locale: WNC
Re: Insulative value of sleep system?? on 02/12/2010 07:23:20 MST Print View

I believe you want ground insulation with a combined R-value of 5 or greater for below freezing temps and you'll be cold with your proposed pad combo.

john Tier
(Peter_pan) - M

Locale: Co-Owner Jacks 'R' Better, LLC, VA
More pad on 02/12/2010 07:37:09 MST Print View

I agree with Chris... thicker pads are needed... Also they need to be plenty long and plenty wide.... Elbows hanging off on the ground is a No-No at Zero...A decent WP ground cloth will help as well.

UL at zero and below is a far cry from UL at 30 and even farther than SUL at 40 or 50 degrees.

Boy scout handbook circa 1950... It is important to put as much below you as above you... Or words to that effect...Of course that was in the days of blankets and blanket pins... :-)


Pan

John Vance
(Servingko) - F

Locale: Intermountain West
Cold Northern Nights on 02/12/2010 08:39:16 MST Print View

I would agree that insulation under you should be at least R-5 for those temps. I have taken UL down to 0f and a bit lower but it isn't for the faint of heart. I use an Exped Downmat 7 full length and it makes a HUGE difference over my Prolite 4 + closed cell.

In addition, If you feel drafts in a quilt set up at 32f, you will find the nights very long at 0f. I would recommend a light bag over the quilt at these temps but if you combine your quilt with a light bag you could wear the quilt in camp and use it to extend a light bag.

This is what I currently use for winter and it works very well.

Steven McAllister
(brooklynkayak) - MLife

Locale: Atlantic North East
Bivy and two quilts on 02/12/2010 08:49:05 MST Print View

I think the bivy would easily add 10 degrees of warmth. The amount of draft that a bivy reduces is nothing to sneeze at in temps that cold, especially with quilts.

I think people put too much insulation on their arms and legs. Tests have shown that your insulation works better on your torso and head. So I vote for a vest instead of a jacket/sweater. Make sure your core and head are well insulated when you sleep and your whole body will feel warmer.

Like they say "if your feet get cold, put on a hat"

Jeremy Gustafson
(gustafsj) - MLife

Locale: Minneapolis
Re: Insulative value of sleep system on 02/12/2010 10:26:16 MST Print View

Thanks for the feedback thus far!

Any recommendations on low-cost sleeping pads for cold weather? Do I just add another CCF pad to my existing system? I do have a Z-Rest, or could I replace the 3/8" pad with my old thermarest? I don't remember the specs on that, but I think it is a 1".

I have used the thermarest plus my z-rest down to about 15F on snow and was comfortable.

Also have used the 3/8" pad by itself down to about 25F, was a little chilly, but manageable.

How about any suggestions on an low-cost lightweight insulated vest?

Steven McAllister
(brooklynkayak) - MLife

Locale: Atlantic North East
Vest on 02/12/2010 11:05:05 MST Print View

I just received a synthetic Golite Caddy, last years model on sale at Campsaver for less than $50.
I went with synthetic because it doesn't compress as much when you wear it and it's good in wet weather.

My sleeping bag is down so I want to at least have my clothing be hydrophobic:-)

Edited by brooklynkayak on 02/12/2010 11:08:15 MST.

Ross Bleakney
(rossbleakney) - MLife

Locale: Cascades
Re: Re: Insulative value of sleep system on 02/12/2010 12:03:27 MST Print View

For low cost insulation, nothing beats closed cell pads. Just bring lots and lots of them. The only drawback is the bulk. If you can't stand the bulk, then you'll probably have to pay for the down filled inflatables.

Excellent point by Steven. Make sure your core (especially your head) is well insulated.

Alex Gilman
(Vertigo) - F

Locale: Washington
Re: Insulative value of sleep system?? on 02/12/2010 12:10:38 MST Print View

You may want to toss this under your blow up bad:
http://www.rei.com/product/783023
For temps below 0 start looking to the mountaineering guys' gear for what works.

Edited by Vertigo on 02/12/2010 12:13:21 MST.

Eric Blumensaadt
(Danepacker) - MLife

Locale: Mojave Desert
Ground insulation on 02/12/2010 17:23:37 MST Print View

The R - 5 recommendation for mattresses posted above seems a bit high.

I'm a cold sleeper but am fine with just my Trail Pro mattress (R - 3.8) when temps are in the teens.

If I knew it was going into the single digits or below zero I'd use my RidgeRest beneath the Trail Pro. But I'd also be using my M.H. 4th Dimension -20 F. Polarguard bag too.

The RidgeRest Deluxe (a thicker, softer version of my RidgeRest) only has a 3.2 R value and Cascade Designs recommends it for winter camping.

Brad Groves
(4quietwoods) - MLife

Locale: Michigan
Re: Ground insulation on 02/12/2010 17:38:22 MST Print View

R-5 is probably about right. Guess it depends on the sleeper and system as a whole, but some pretty reliable research on the subject. Personally shoot for ~R-6, ~R-8 for subzero. Sleep comfy warm! Remember, ~35% of your insulation comes from underneath you (if a back sleeper)... See the following threads:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=25754&disable_pagination=1

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=24000

also consider:
http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=27625

20*F below zero is not a time for screwing around with a stack of pads that you hope might be warm enough... Realize that there's a lot of difference between systems that work at +15*F and -20*F. Kinda like the difference between systems that works at 15*F or 50*F... Gotta say, a Downmat 9 is the way to go for deep winter.

Edited by 4quietwoods on 02/12/2010 17:44:40 MST.

Chad Miller
(chadnsc)

Locale: Duluth, Minnesota
Insulation value of sleep system? on 02/12/2010 18:27:23 MST Print View

As a backpacker with a few seasons in northern Minnesota during the winter I agree that shooting for an R-Value of 5 for your sleeping pad is a good idea. Personally I like to use two long sized RidgeRest pads. I do not like to use self inflating pads in the winter as they take a long time to loft up, and they seem to loose a good deal of insulation through their sides when it's below 15 degrees.

For my sleeping bag I will typically still use a zero degree bag until the end of Feb. If the temperatures look warm then I will take a 20 degree bag and augment it with the high loft clothing I'd be taking anyways. For me personally I've found that trying to boost the warmth of bags lower than 20 degrees with insulated clothing actually becomes heavier and colder than simply using a warmer bag with a draft collar.

Edited by chadnsc on 02/12/2010 18:29:57 MST.

Steven McAllister
(brooklynkayak) - MLife

Locale: Atlantic North East
R-5 on 02/12/2010 18:50:49 MST Print View

I agree with Chad, you loose a lot of heat through a low R sleeping pad. Having a huge amount of insulation up top doesn't do much good if your body heat is going into the ground. This is especially true if you sleep on wet, frozen or rocky ground.

Now if you can find a pile of relatively dry leaves, then the R factor of your sleeping pads doesn't matter:-)