cold air return

[allmetalswelding]

I have recently purchased a 2.5 storey brick house. Cold air return ductwork hinders basement remodelling. The house was built in 1910, before forced air heating systems. There is presently a gas furnace with ductwork to the 2nd and 3rd floors with no cold air returns on these floors. The main floor has 3 returns. How critical is the cold air return if enough make up air from open doors reaches the furnace?

Thank you

 

[willard3]

Not critical if you don't mind heating the outdoors.

Critical if you want to be warm and comfortable and not spend a fortune.

 

[RossABQ]

I assume he means the doors to rooms on floors 2 and 3, not to the outside, so that air can work its way back to the 1st (main) floor. In which case there is no problem.