Question: adding layers to sleeping bag

[G-FOURce]

If I am using a bivy sack, does it matter if I add a layer of insulation, like a fleece blanket, to the inside or outside of my sleeping bag to improve warmth? Not knowing anything about thermal dynamics, my knee jerk reaction here is that on the inside would be more advantageous. However, I'd like to retain as much heat as I can and I am hoping someone here may have some insight. Thanks.

[yellowsirocco]

If you put it on the outside the weight of the fleece may crush the insulation a little. I would use it on the inside.

[Nutbrown]

I've not used a bivy sack before, but earlier this year I camped in pretty cold weather with a bag that was not warm enough. I used my down underquilt in addition. I hooked the uq over my bag and it held in place with the bungee cord tucked around the under side of my pad. Warm and toasty, I was!

The only thing you have to worry about is if the added insulation has a waterproof coating. If it's fully breathable, tuck it inside with you. The wp coating on the bivy will help to keep your heat in.

[bear bag hanger]

I'd vote for putting the new insulation inside, provided it doesn't make the inside too tight or cramped. Putting it on the outside may subject you to cold wind that could blow your warmth away.

[Frog]

If you need to add warmth to a sleeping bag get a liner they add around 10 degrees warmth and the added 10 degrees from a bivy sack should be enough. If not you need a warmer sleeping bag.

[RodentWhisperer]

+1 on putting the insulation inside the bag. That would trap more warm air within the bag, and would reduce the compaction of the bag's top layer.

Just as an aside: I've found that wearing my down vest under my quilt adds about 5-10 degrees F. I know that down pants are made/sold by a few companies; so are down booties. It might be worth investigating the cost/benefit of gathering everything you'd need to make some, um, "down PJs." :-)

[Franco]

If I am using a bivy sack

I use puffy clothing inside my bags rather than two layers. A benefit of that is less cooling from air movement against my body when I turn and much nicer when I get up for a pee.

If that does not work for you , putting the extra layer inside or outside would depend on a couple of things.
If you are using a down bag, go outside.(between the sb and the bivy)

It has been measured that up to about 50% compression down works just as well as non compressed.
(Richard Nisley, BPL)
(Some confuse the total compression under a body with partial compression...)
The reason for this is that you will have some dampness between the bag and the bivy so that would migrate to the synthetic layer on top rather then the fabric layer of your sb.
Now, if you are using a synthetic bag, inside would work better as long as it does not restrict your movements.

[Franco]

BTW, I am assuming that "a fleece blanket" refers to a 10-20oz job not a 4 LBS home type blanket...
When I drape my 15oz quilt over an sb I see no measurable difference in the sb loft.

[leaftye]

Just looking at weight alone, it'll take much less fleece to line the inside of a sleeping bag.

[G-FOURce]

thanks, everyone... lots to chew on here.

[dornstar]

If you fly, snag an airline blanket.

They weigh about 5 ounces and are a good size for inside a bag. Not sure how many degrees they add, but it's a nice, light, small pack size option.

[Franco]

"snag" sounds so much better than "steal" doesn't it ?

[Nutbrown]

eh, I think you pay for every last bit of 'comfort' supplied by the airline. They are charging for blankets and pillows from what I've heard.

[Franco]

Hotels have the same problem too "it's built into the price"Shoplifting is also built in to the cost of goods, so just go ahead and help yourself.

[G-FOURce]

i fly quite a bit, but unfortunately not for a couple of months for now. i'll see what i can find at the fabric store

[Wise Old Owl]

Change your clothes add a fleece beenie and fleece glove a personal favorite is the ones with a fold back clam shell so you can do fine dexterity... winter Under Armor top and bottom or anything with polycro. - please list the bag in future.

[G-FOURce]

Change your clothes add a fleece beenie and fleece glove a personal favorite is the ones with a fold back clam shell so you can do fine dexterity... winter Under Armor top and bottom or anything with polycro. - please list the bag in future.

i am considering a 35* 800-fill down sleeping bag. i am a warm sleeper and would want to be able to get the bag down to about 25* if i can without having to purchase another bag. i am going to sew this first pass at an "over-blanket" to see if it works. if it does, then i may consider a second pass at it filled with down to go a bit lighter. i'm not married to this idea, just thinking about it...