Return Duct CFM Question
I have a return that is mounted in an interior wall between the studs.
It has a 16x20 grill with about 10 ft of in-wall duct running down into the crawl space, where it connects to a 12" flex, and runs back to my air handler (about 25 ft).
How much return CFM can I expect from this return?
Would increasing the diameter of the flex give higher CFM (or is the in-wall duct or grill the limiting factor)?
What size flex should I use to best use this return, and how much CFM would it deliver?