Originally Posted by
cyccommute
Yes, the heat goes up but it is then trapped in the envelop of the rain fly. It doesn't get swept out immediately or even quickly. I've slept many nights with the door open only to have to close it in the middle of the night. The temperature difference is immediately noticable. I've also started the night without a fly at around 10,000 feet only to have to get up in the middle of the night to put the fly on. Again, the results are immediate. Trapping the air (and heat) from your breath helps.
For most tents, perhaps. The primary thing I like about that tent is excellent ventilation. The fly is very different from most; On the narrow sides, it goes to near the ground. On the front and back of the tent, window and door sides, there is a 3rd pole for only the fly that goes on top of the tent, little bending, holding the fly at both ends only about an inch below the tent peak, so the fly on those sides is really just a slight overhang of the tent on those sides, designed to keep rain off the mesh windows when zipped open, and even then, marginal at that. Thus, wind, even the slightest breeze, blows right through from front to back of the tent. Even with zero wind, because almost no curvature in that direction, nearly flat, any hot air goes sideways and then leaks up and out from under the fly. Great tent for hot weather, as cool as leaving the fly completely off, at the expense of no vestibules on either side. Terrible tent for colder weather, it just keeps in zero heat. Not what it was designed for. In a cold emergency, leaving that 3rd pole out and letting the fly drape down on both front and back and secured, while still allowing a bit of vent via air coming from the sides under the almost full-coverage ends of the fly, I'm sure would help a lot.