I'm considering removal of the cold air return duct work and making my own duct work up in joists, much like is done in other parts of the basement. However, the other areas run with the joists and actually use the joists as part of the return duct. In my re-work scenario, I'd like to run the duct work horizontal to the joists.
My concerns are:
1. How big of a hole do I need in the joist to support the correct air flow.
2. How much will a hold affect the structural integrity of the joists.
Any advice is much appreciated.