What material can this be used with?
This vent is specifically for drywall / gypsum wall and ceiling surfaces.
My drywall is already installed, can I use this?
Can this be used as an air return?
Yes it can!
Can this be installed in engineered floor joist systems with the use of TJI joists?
This vent is designed for standard joists. With TJI joists you may have to be aware of sizing.