Jim: Interesting that your experience has shown that you must vent the tent. This is what I would anticipate having to do.

This approach does run contrary to the original brochure:

"Please note: If you you should begin to experience any condensation inside the tent, CLOSE the door securely and shut the back vent. While this may run contrary to normal logic, the reason is simple. With the tent shut tight, your body will warm the inner air and create a higher vapour pressure inside the tent than outside. This in turn will force the moisture laden air out through the microporous Gore-Tex membrane. Leave the back vent open only in very hot weather when you want actual air movement throught the the tent.

Once again, in humid conditions, you will find that the tent will be the dryest when the vent and door are CLOSED."

Perhaps the manufacturer is referring to temperatures higher than freezing.

Thanks for your input.