One Quilt or Two?

If you consult the table below from EE, it seems to corroborate  your impressions…

http://www.enlightenedequipment.com/blog/quilts-106-quilt-layering-for-cold-temps/

Thank you for that! The formerly mentioned old BPL calculation brought the temp rating  with the two quilts down closer to 10 or 20* if my memory is correct and although I wasn’t cold in the low 30’s with both quilts I was surprised I wasn’t as warm. The EE table seems more accurate.

I think it’s probably more complicated to compare the two than most realize.  A lot of folks talk about depth of loft, and while that is the main factor, there are other minor factors that contribute.  With two quilts on top of each other, you’re factoring in extra convection conservation and a trapped air layer between them.

As far as warmth to weight efficiency though, a single quilt or bag of equal loft will often beat out a two combo, unless the former uses low quality insulation and both of the latter use very high quality insulation.  In more practical terms, a single synthetic qulit of a certain loft depth, may weigh as much as two quilts with 850 or 900 fp Down, that also have UL liners/shells.

The WM Everlite’s sold as a bag liner as well as a summer quilt. I was told by the Production Manager that it adds approx 5F to the rating of any of their bags, which doesn’t seem like a lot, but the stitch-through design is inherently less efficient than a box-wall. That should be taken into consideration too.

the everlite should add more than 5F … more like 10-15F at least to the temps …

in very general terms a 40F summer bag should add around 20F+ to a rating conservatively

even the el cheapo 20 dollah costco down quilt will add 10F+ … in fact its the cheapest way to boost your bag temps

a single bag of the same weight and quality will always be warmer than two … especially if the top one is synth

however using a synth overbag allows very good moisture management … all the body vapor goes into the synth quilt, and any outside condensation will also hit the synth which dries very quickly … the inner down bag stays very dry

also one can use the synth in camp without worrying too much about it …

;)