I am making a quilt using .51 ounce cuben 30d reflective nylon and 5 ounce climashield apex. My question is would it be more efficient to use the reflective nylon as the liner. Or to use it as the outer with the reflective side facing the insulation?

Assuming your 'reflective' nylon has a metallic coating, you want the nylon as the outer shell with the reflective side on the OUTSIDE. The most useful property of the of the metallic coating is not it's reflectivity but it's low emissivity, particularly in the infrared spectrum. In other words, the reflective surface will radiate less heat. But, you will look like a roasted turkey :o

there was something on this a while back by the insulation guru himself. He said for a reflective layer to work best it had to be about 3/4" away from the user if i remember correct, so it seems like that advice suggests as the shell reflective side toward user with insulation then liner against user. I am just trying to remember an old post and don't have the link sorry. It may be hard to measure as you are combining reflective heat collection and vapor barrier heat collection methods. It may be hard to say which one has the most impact on warmth. If the reflective layer only boosts warmth a small bit over VB you would be better served using cuben on both sides and saving the weight, i just don't know how to measure them separately.

-Tim

I bought a 1.5# sleeping bag with reflective lining from Herter's in the early 1970s. The outside (I think) was clothing grade tyvek. That thing kept me more warm in an amazing range of conditions. I think it was way ahead of it's time. Or I had a great metabolism for a 12 year old.

Edited by skinewmexico on 11/12/2011 13:33:12 MST.

I think it was Backpacker Magazine that evaluated reflective liners back in the day when "Texolite," a mesh-protected, perforated foil, and some other reflective barriers were being tried by several bag manufacturers.

The conclusion was that the reflective barriers lowered the degree ratings of the bags when placed just inside the inner shell, but not when placed inside the outer shell. Sorry I don't have the article for you. At that time, Backpacker was doing a pretty good job with issues like this. As I recall, however, the reflective liners were all perforated, and the bags were vapor permeable, not VBL. Don't know if VBL would make a difference.

At that time, I bought a 'Yaksack' from Yakworks, that used Thinsulate with a Texolite layer just inside the inner shell. It was amazingly warm for its 2 lb. weight. I recall using it at the old Tamarack shelter in winter on Killington Mtn in VT and not being cold at all. Then I washed it a few times, and it became no warmer than other synthetic bags of the same weight. It couldn't have been a loss of loft, because the Thinsulate didn't depend on loft. The shell was laminated to the insulation, and the bond was lost; but I don't see how that would affect the insulative value. So I stopped using it. It's always been a mystery.

Take a look at a company doing something similar for decades with their sleeping bags. I've never used or even seen one, but they might know something about this. Look for the section called "Radiant":

http://warmlite.com/sleeping-bags/bag-technical

I used to work for a company that invented the soft coolers.
http://www.cooltote.com/

Their insulation for the tops and sides of the coolers was polyester fiber woven right through aluminized mylar film. It worked very well and
sounds like similar stuff to the Yak bag.

Washing removes the aluminum from the mylar.
In addition, since the only structure to the short fiber insulation layer was
basically a version of the cheapest of space blankets, the mylar could be easily torn
leaving big gaps without any insulation.

In the end, tho that type of insulation worked well when protected by two thick layers
of pack cloth in a cooler bag, it couldn't handle the strain of being sleeping bag insulation.