# Thread: Temperature rating of multiple layers in a sleeping system

1. ## Temperature rating of multiple layers in a sleeping system

Hey guys,

Just a quick question. When adding things such as outer or inner sleeping bags, or something like the softie suit, do you just put their temperature rating on top of everything else in the system, add all the rating together and that gives you the overall rating of the system? I'm thinking that's too simple and probably unlikely, but I like to check these things.

Cheers,

Matt

2. What you have to watch when layering up "lofted" insulation is that unless each layer can "loft" to it's full potential then it wont trap the heat. So each layer has to be big enough to accommodate the other.

3. The hammock forums explanation is reproduced below. not tried it in celcius as all my bags are american and rated in Fahrenheit.

"First estimate: take the liner bag rating subtract it from 70, divide that number by two and then subtract it from the outer bag rate for a combined value ex

Two 40 degree bags... 70-40 =30 devided by 2 =15 subtracted from other bag 40-15=25 for a first cut estimate of the combined bags... it may actually be better but probably not worse, so this works as a good conservative estimator, IMHO"

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