Inflatable Sleeping Pad Inside Mummy style bags?

[Scott N]

I’ve been messing around with this because I have found it comfortable, I’m sure a lot of folks would not, and have actually found it to “feel” warmer. I’ve read in a few places this should make me colder, and was hoping for some experienced folks input if there are any potential pitfalls I should be aware of, or a better understanding of how a sleep system ideally works since it seems that very few people put their pads in their bags. For more info, I’m fairly small 5’8 and 140 pounds. Standard sized bags offer me a generous amount of room, so maybe larger folks are finding too much of the bag filled with a pad inside it? The pads and bags in question, mixed and matched depending on conditions: sea to summit ultralight .7 R value, sea to summit ultralight insulated 3.3 R value, Marmot Hydrogen 850fp rated to 30 comfort, and Sea to Summit Spark sp1. I also have an aegismax mini, and nothing is fitting in that thing besides me.

I started doing this because I also have a Thermarest Navis that has no down fill and baffling on the bottom, just fabric and pad attachment straps… it works great.  I suppose the design considers that insulation that is crushed doesn’t serve any purpose. It seems to me putting a pad in a bag is similar… though I have some wasted fabric on the bottom touching a shelter floor, pad insulation, my body, then bag insulation, going from the ground up. Thoughts? What am I not considering here?

[Dena Kelley]

I don’t see anything wrong with it. The Klimit Inertia O Zone is designed to go inside the sleeping bag. I honestly think if it’s comfortable for YOU, then it’s right for YOU.

[Bob Moulder]

I concur with Dena… hey, if it works for you.

But I would point out that it might be working for you because perhaps you’re not pushing the limits of the system, so I’m wondering, what are the lowest temperatures you encounter with these sleep systems? Does the bottom of the sleeping bag get wet from condensation? What is the total weight of each system?

When seeking the lightest system possible for a given low temperature, maximum efficiency of insulation is a must. A somewhat heavier system won’t require as much tweaking.

I have a system that works for me down to (at least) -6°F for a total weight of 2.8 lbs. It consists of a +20°F-rated EE Enigma quilt (~22oz), a TR Neoair Trekker torso air mat (13 oz), a full-length 3/8″ CCF pad (7.5 oz, which goes on top of the Trekker) and an Exped UL Pillow (2.6 oz), with my pack under my lower legs. Critically, this is complemented with my EB down parka and Montbell down pants, which are items I carry anyway when it’s really cold… so those fall into the much-coveted “dual use” category. I did a LOT of testing to tweak this system. It works for me.

Edit: corrected… my CCF pad is 3/8″, not 5/8″

 

[James Cahill]

I’m tall with broad shoulders so I generally wouldn’t have room to do this, but how I saw it explained once was:

Inflatable pads suffer from circulation of cold and warm air inside the pad. As your body heats up the air beneath you, it circulates and flows to regions where the pad is exposed to cold air, cooling it and acting like a heat sink. Insulation-filled pads solve this issue by preventing air from moving as much. If your pad is inside your bag and there is enough room to keep the bag’s insulation from being compressed on the sides, then the bag is also insulating the exposed sides of the pad from the cold air. However, this does not prevent the cold ground from cooling the air within your pad as the compressed insulation of your bag beneath the pad offers no help. So if the ground is cold, you still need an adequate pad. But when your air pad is inside your bag, all the surfaces that would normally be exposed to the cold air are insulted by the bag. If your pad is too big, then you end up with lots of dead air inside your bag and the efficiency decreases. CCF pads of course do not suffer from this as there is no air movement.

But again, I only read that and haven’t tried it myself! Like Dena said, if it works for you it works. And like Bob said, you may find it not working as you approach the limit of the system. Have fun with it!

[Scott N]

Thanks to Dena, James (pondering the physics) and Bob. It may be I’m not seeing systems break down near their limits because like Bob I’m using a down layer.

<span style=”line-height: 1.8;”>For Bob, I’m not going out in temps as cold as you… but we use similar systems. I always bring a Montbell UL down top, 7oz… and the superior down pants, 9oz. These often wind up being part of my pushing the boundaries of a bag, dual use as I will wear them around camp at night. The three bags in question are an Aegismax mini (15oz), Thermarest Navis (20oz) and Marmot Hydrogen (23oz). The Marmot and Thermarest weigh in under spec, no idea why. I would never take the Navis or Aegismax without a down top and hat as they are hoodless bags. The insulated S2S ultralight pad comes in at 15oz (i have the short) and the not insulated at 14 (regular, cause it makes a fun floatie). They are 3.3 and .7 R values respectively.</span>

I’ve been up at Lake of the Angels in Olympic National Park for the past couple days, hence the late response to the comments. Kept camp there for three days and mucked around Mt Stone, Mt. Skokomish, Hagen Lake, Stone Ponds, St Peters Gate… if you’re a scrambler and not a real technical climber like me this whole area is a blast, not to mention beautiful. For this trip it was in the mid 40s at night, I took the Aegismax and the S2S insulated, wore down layer when I went to bed, wound up taking it off. I did unzip the Aegis and sleep directly on the bag in an REI baselayer. If you count the down this is a 15oz pad + 15oz bag, plus 16oz dual use down layer. A forecast at 35 and I’ll switch to the thermarest, a forecast at 25 and I’ll switch to the Marmot. In each case I’m pushing the bag 10 degrees past it’s EN… well, the navis doesn’t really have one.

Condensation is a given here in the Cascades, and since I use a lot of down I can be a bit neurotic about it. I’ve not seen any condensation between a bag and groundsheet yet, including this weekend when I tucked the aegis under the bag like a quilt. When my photos finish uploading I’ll tag a picture on this post… it will give you an idea of how much time is spent at the dew point during the day up there!

I like my systems, but you’ve got a great cold weather system. I might replicate it and give you credit amongst all who will listen on my hikes.

 

 

 

[Scott N]

As promised, a little Olympic National Park condensation!

[Bob Moulder]

Wow, what a beautiful location!

Good example of how condensation is never far away in some places.

[brian H]

i have been using a t-rest prolite pad inside of a down quilt, w the straps wrapped under the pad,..and the quilt edges tucked under the pad, held snug by said straps, successfully trapping my body heat in the cozy envelope, and preventing drafts. it’s been working 4 me.

am looking now for a tapered NeoAir to gain more cushy padding, as my rectangular one doesnt fit…

[Franco Darioli]

Since it works for you, keep doing it.

Not all that different from folk that use a top bag having a sleeve at the bottom to insert the mat into it.

BA still does that but WM and Macpac ,amongst others, have used that system in the past.

The reason more don’t do it are that many do not have the space for their mat inside the sleeping bag and or because they turn during the night taking their bag with them when they do so.

Doing that you end up with the mat above you and you on the ground.

[James Marco]

I have used an older NeoAir original inside a Marmot a few times. It works better than leaving the pad open to the cold air, IMHO.

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