Originally Posted by
4eyedbuzzard
THIS^^^
A tent may be 5°F warmer, but only under conditions when condensation is not an issue. Mostly, they increase warmth because they protect you and your bag from drafts and direct contact with ambient air, settling dew, etc.
But, the warmer a tent is inside relative to the outside air, the more you will fight condensation - especially in a single wall tent. The less ventilated you keep your tent, the warmer and more saturated the air (both atmospheric plus water vapor expelled breathing) inside the tent becomes. Then, when it's humid out as it often is in the eastern mountains, as the temp falls at night the low mass tent fly fabric cools almost instantly with the outside air temp, and the moisture in the relatively warmer air inside the tent condenses on the cooler tent fabric. It is unavoidable.