In our home, the previous homeowners finished the basement, but only put one cold air return in (on the ceiling no less).
I can get to the return air duct, for the upstairs bedrooms, in the ceiling of one of the downstairs closets. I can tie into this duct in the closet, and run it down between the studs in the finished walls, and add 2 more cold air returns in the 2 downstairs bedrooms.
If I do this, will it cause the returns upstairs to draw too little air? I know they all end up in the same place, but would like to be sure before I start cutting holes.
Should the downstairs returns be run in their own ductwork?
Getting some of the cold air off the downstairs floor should surely help in cooling the rest of the house.