The volume of air being moved out of the ducts from the furnace should be the same that is returning to the furnace. If air goes into a room, there should be a way to return to the furnace in the same room if the door is closed. The basement was heating up much faster than the living area when I first started. A service rep from a local oil company suggested that I open up the duct work and put in some more returns. Something was bothering me about putting a cold air return under the stairs on the main floor. On the Building Science Corporation site their is much useful information for buildings. Their I found a diagram that shows hot air going across the floor back into the return air ducts. Also there was a diagram showing heat coming from the floor to the ceiling. Putting a cold air return on the second floor was not too practical, but I did it anyway.
This is a view from the 3rd floor at the wall being expanded for the duct. 2 X 4 walls do not big enough for the air flow, so the wall was moved out by 2" to allow more air to flow.
Here is a shot of the first floor. Here the wall is being expanded and a hole cut through to the basement.
This is the finished wall on the second floor except for the paint and duplex covers.
The finished wall on the first floor.
The opening up the cold air returns has helped the air flow throughout the house. A cold air return was put into the bath and bedroom on the first floor. Upon testing the expanded duct works, we set the thermostat at 68°. A later in the evening, I found Dewey in the Great room and asked him if he was going to bed. He said he was there but the bedroom is too hot! Whew, at least the mother-in-law was not complaining about being too cold.