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.
While I agree that there is no insulation value to nylon, that does not mean that the tent is incapable of trapping heat. All tents trap heat from the occupant(s) body. The heat isn’t immediately swept away as long as the rain fly is in place. Without the rain fly, air very quickly dissipates…something I’ve experienced when I left the fly off because the night was hot only to have to get up in the very early morning to put on the fly when the temperature dropped about 60°F. Rain flies are meant to be water impermeable which means that they are also good at keeping air from being swept out of the tent.
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).
The air in the tent is going to be still. There is little movement of the air from the inside to the outside which keeps the heat inside the tent. The air in the tent is also moisture laden (breath is saturated) which means it can carry more heat. However ClydeClydeson is slightly wrong in that this is a volume problem, not a surface area problem. More space requires more to heat it. A single person in a large space results in the warmed air to move further away from the body that is warming the space.
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."
Huh? I use the “I got colder on this trip than on that trip” argument because it happened. I used the same bag and pad in both tents that I compared above. I took into account the different temperatures, humidity, altitude, and wind in both cases. Camping at 10,000 feet is very different from camping at 4000 feet. The 10,000 foot camp was in the small tent with morning temperatures in the 30°F. The 4000 foot camp was in a large tent in 40°F temperatures. The lower camp was much, much, much colder.
By the way, I used that same tent on a trip with my daughter at 700 feet in the Arizona desert, albeit with a thinner bag, at 40°F temperatures and it was far colder than even the 4000 foot camp trip by myself.
I’ve camped in all kinds of tents and conditions. I’ve done extensive camping in 2 man and one man tents by myself. The one man tent is much warmer.