Originally Posted by pdlamb

Problem with that is that the insulation value of a mil or two of nylon and polyurethane is pretty close to nil. The temperature gradient (not the temperature difference) is the other factor in heat transfer, and with nothing in the way of insulation, the heat flows right on out.

Two more things. First, since the tent wall provides approximately no insulation, the air between the sleeping bag or sleeper and the tent wall is left to provide all the "tent insulation." You can argue that less distance between the sleeping bag and the tent reduces the chance for convective air currents to dissipate heat. It kind of even makes sense, but I'm not aware of any models or measurements on this hypothesis (and I'm not an aerodynamicist, so I couldn't provide one in less than a few years' of college that I'm not interested enough to invest).

Second, those who don't see the problem with "I got colder on this trip than on that trip" kind of argument, should perhaps engage in trollheim political arguments rather than this discussion. If you're slightly suspicious, consider whtehter different temperatures, relative humidity, altitude, wind conditions, and even whether personal preference might influence the "observations."