Greetings all. We live in Wisconsin and our home was built in 1994. It's a 1700 sq. ft. ranch with AC. There are cold air returns near the floor and near the ceiling. However the ones near the floor are the only ones that can be closed. Is this right? Or should the closeable ones be near the ceiling? To me is seems to be backwards. It just seems to me that you would want the ones near the ceiling closed in winter so you aren't pulling warm air back into the furnace. What do the pros think?