Quote: The basement is heated and cooled, so most of the heat IS coming from the heating system.
Whether or not it's directly ducted is not relevant
Quote: The AIR in the basement is being blown out at a rate of 50 CFM, or 3000 CF per hour
That is slighty less than the amount of air in a 20 X 20 room EACH HOUR
That air has to be replaced, and any incoming COLD air will end up cycling through the heating system and the entire house, unless of course there is a basement window open to let air in
It's simple physics
When you vent a given volume of air OUT of an enclosed space, you have to eventually allow an EQUAL amount back IN to equalize the pressures
Whether or not it's directly ducted is not relevant
Quote: The AIR in the basement is being blown out at a rate of 50 CFM, or 3000 CF per hour
That is slighty less than the amount of air in a 20 X 20 room EACH HOUR
That air has to be replaced, and any incoming COLD air will end up cycling through the heating system and the entire house, unless of course there is a basement window open to let air in
It's simple physics
When you vent a given volume of air OUT of an enclosed space, you have to eventually allow an EQUAL amount back IN to equalize the pressures