Originally Posted by
UnCruel
Heat moves from the warmer body to the cooler body until they reach the same temperature.
But there is a rate to the transfer. It isn't instantaneous
Condensation is the conversion of a gas to a liquid. To bring this tangent back to the original topic, if you close up your tent to try to seal in the warmth, you will cause water to condense inside the tent. If there is a significant amount of condensation, it will run down the walls of the tent, and much of it will find its way into your sleeping bag. Whether or not we agree on the physics, it's a thing that actually happens (though probably not much at 40°F).
Yes, condensation is the conversion of gas to a liquid. However, in a modern well designed tent, none of that water that is condensed from vapor gets to the inside of the tent. Even if it did, the amount of water is minimal and certainly not enough to wet sleeping bag insulation to the point of making it ineffective at insulation. We breathe out roughly 0.6g of air with each breath when at rest. That contains about 0.02 g of water in the form of vapor. At 960 breaths per hour for 8 hours, that's a total of about 150 mL of water expired. For the metrically challenged, that about 2/3 cup of water per night. Even if the entirety of the water were to end up on the bottom of the tent that is hardly a flood of water capable of wetting a sleeping bag. Since most people use some kind of pad, it's not even likely to even dampen the pad.
Originally Posted by
Duragrouch
My experience was that 1 and 2 person tents were about the same temp in cold weather, as they are very well ventilated (lots of mesh area under the fly cover) to not accumulate condensation, if not a winter tent. If your body is heating up the tent, your sleeping bag is not doing its job.
The heat doesn't come through the sleeping bag. It does its job by keeping the body heat close to the body...a bit like a smaller tent does
. But with each breath, you are releasing heat into the tent. Your breath has to heat a larger volume with a larger tent.