On Tuesday, December 6, 2016 at 9:08:46 AM UTC-5, cln wrote:
Return air surface area should be like 125% of total output surface area -
more if the return path is long .
^^thanks Terry

Wow, I'm surprised my ducting hasn't buckled! I will add some returns in the basement since there's only 1 for the Air Exchange (4"). The kids bedrooms are also a bit cold so I might add some returns there as the hallway air return doesn't seem to be enough.



What kind of basement? Finished or un?

AFAIK they don't usually put returns in an unfinished basement due to dust
and typically colder air. (I could be wrong, but that was my understanding.)