I have a approx. 1000 sq. ft. house. Built in 1959. It has a cold air return in the hallway and a split cold air return between the two back bedrooms. Is there really a need to have all three, or can I seal off 1 or the other?
The multiple cold air returns help distribute the heat more evenly through the house. It also "balances" the return and supply requirements of the furnace. I would not block any of them. Is there a particular reason for blocking them?