I assume that since the builder went through the trouble to put that in, that it's necessary.. but why is it necessary? Isn't there enough air in the house for the furnace to use? The furnace has been running for at least 4 years without it. I'm willing to repair this, but I'd like to know the reasoning behind it. I've found out that vent is a pretty major source of cold air coming into the basement.
Another bit of information: The house is very drafty, so there's no concern about it being so sealed up that all the oxygen is gone. LOL