Pushing a Sleep System Further – Top vs Bottom

Okay, this will be instructive. I look forward to reading experiences from others.

Next winter I plan to venture further north!

My opinion… The pad.

If your bag is truly rated to 20 F, then replace, or better yet, supplement your pad with a ccf pad, even just a 1/8" pad. You can use extra clothes to add insulation to the top, as well as a proper shelter to block wind/trap heat to get the most warmth from the top, but once the bottom gets cold, the only thing that helps is more insulation. And it's surprising at how much extra warmth even a 1/8" pad can add when layered over the top of the Exped UL7 pad.

The first time I ever used my SunMat UL7 the temps were 6 F inside the shelter on the AT, with wind blowing against the back and under the floor of the shelter. The boards on the floor were spaced apart a bit more than normal, so the gaps were a great place for heat to escape. Since I was expecting cold temps though, I carried a 20 x 59 1/8" pad and a 20 x 40 1/4" pad. I put the 1/8" pad down first, then the SynMat, the the 1/4" pad on top, and it worked. On top, I used my Marmot Helium 15 F bag, and wore a pari of down pants, sock, cap 2 long sleeve top and cap 4 1/4 zip hoody inside the bag. I also had my MB Ex Light down anorak, but didn't need to put it on, instead, I just crammed it inside the sleeping bag next to the zipper to fill space. I stayed plenty warm and feel like I could have dropped a few more degrees before getting cool…

Chad

I'm not looking so much for how one can supplement their sleep system (i.e. – CF pads, additional clothes, wear your puffy, etc.), as we all do to thermally regulate ourselves to the current weather conditions. Rather, I'm looking to find out what others feel or know (technically), in their experience or testing, is a better place to invest the weight of an upgrade in…the insulation below you, or the insulation above.

That is to say, is your heat better retained with a slight boost below you or above you when pushing your insulation to it's limits?

…The focus of this question being on the two pieces of insulation that cover most of us from below and above, our quilt and our pad.

I'm not dissuading others from sharing stories and stating what they were using at the time…just remember to ultimately target answering the question above, be it technically or non-technically.

So Chad, to come back to your experiences, considering your insulation was pushed equally above and below you to it's limits… where would you find a more sufficient gain in warmth, from your pad of from your quilt? What would curb that "borderline chilled" feeling better?

HTH

KJ

Here is a classic thread that I bookmarked years ago and still refer to on occasion. It is not quite what you are looking for but it is a start. It primarily addresses how mattress insulation affects system warmth when using a ~28 degree quilt. Scroll down about 2/3 of the way on the first page to see the colorful table. I will not do all the legwork for you but it should be easy to find weights of 1/8 inch thick, 1/4 inch thick, etc. CCF pads. That, combined with a very rough 3 ounces of down in a quilt yields 10 degrees F warmth should give you some numbers to play with to make a *rough* determination of CCF vs. down weight efficiency. I would not push this technique very far but for small changes of an ounce or two on top or bottom it should work (fingers crossed).
I look forward to seeing what you come up with.

BPL Thread of interest: http://tinyurl.com/ogvpxmw

Likely depends on which hits its limit first.

I've used my 30F rated quilt at >50F, and as low as -2F.
It probably goes without saying that I sleep exceptionally warm, but the only part of my sleep system that really changes in between 50F and the mid teens(where I have to add insulation beyond warmer baselayers) is the pad.
From ~30F and up, I use a r2.2 Thermarest Prolite small. Somewhere right below that, it's not enough any more. When temps get lower, I switch to a full-length r5.9 Downmat UL 7. I've used both pads in the 30s, but find that I sweat a lot from thigh to waist if using the Downmat above freezing.

It was the same with the 40F Marmot Arete sleeping bag I used most of the time before switching to quilts last year. I've frozen my butt off cowboy camping at ~40F with a r1 Big Agnes Air Core, but was fine at freezing in the same bag wearing boxer briefs and a Capilene 1 shirt with the r4.3 Insulated Air Core. Adding midweight top and bottom baselayers has also let me sleep comfortably with that combo into the 20s.

So, for me, the pad makes a big difference.
I imagine that each person's individual limits with their own gear are something they have to discover for themselves, though, because we're all different.

John

Thanks for the link. Good info there.

KJ

For mid to low 20°F, I've noticed a difference of warmth on my backside if I'm sleeping on snow or bare ground. When on bare ground at those temps my TAR Prolite Plus (R 3.4) feels warm against my back, but on snow as the night progresses it will start to feel cool. My top, feet, and noggin are still plenty warm in my bag (20°F mummy), so I've since added a CCF to the equation if I know I'll be sleeping on snow and I'm now warm throughout the night.

To try to answer your question, for me it was adding insulation below.

Bottom for me. So adding the CCF reflective zlite saved my bacon in colder temps and unexpected ice and snowstorms on thru hikes, especially when adding clothing was not an option. Back when I used to carry more weight the Big Agnes Q Core with just a tyveck sheet underneath was fine, but since getting a lighter pack, and older and skinnier I use the zlite year round and I can use a 3/4 inflatable for torso (insulated one for freezing and below) and put my pack under my legs and be comfy. In fact I've worn my zlite out, time to get a new one!
One thing to note for you younger folks…..when I was in my 20's and 30's sleeping on the ground with a good sleeping bag and just plastic underneath was tolerable, so I did it for months on end during thru hikes and I'm sure it led to joint and arthritis type stuff later for me, so take care to not do that if possible because the abuse adds up and you'll definitely feel it later on in life.