I have one 10x24-inch cold air return grill near the centre of the first floor of my 1200 square foot, two story home. Is there a calculation that can be used to determine the total correct grill or duct square inchs required to properly supply cold air to the furnace? Should I try to retrofit a return on the second floor or in the basement?
Answer:
People who do ductwork will be able to help you with the calculations. A lot of it also depends on room configurations but if you have a return air grill near the stairs, you might not even need another one upstairs. I'd be more concerned with making sure that each room in the basement is service by a return air grill.
