My furnace has an adjustable louvered vent on the cold air return.
All of the rooms have cold air return also.
My question is:
Should the louver on the furnace be open or closed in the winter?

Thanks,

Jon

That really depends why the louver was put on the return air to start with. You might have a marginal return duct size and that the added vent was put there to make up for the small duct. There is nothing wrong with leaving it open as long as it is not in the room with the furnace. Taking return air from the same area as the furnace is a NO NO.