Just looking for a quick answer. Found that 2 returns in the bedrooms upstairs empty into space(not wall cavities. The air goes under the 2nd. floor space and there is a small opening that leads into a wall cavity that leads to the downstairs return. this means that any air under the floor(dust, dirt, etc) gets a chance to be sucked in.
To make a long story short. I found that I can run a flex duct through the upper part of a closet from each bedroom. It runs into a metal plate that I made and 2 6" take offs. It will enter the wall cavity perpoendicularly. I sealed the space above where it enters. I know it is not the ideal conditions, but it is 1000% better than having air very lightly sucked into the 2 grills and just mingling with all the air under the 2nd. floor.
My question is simple-should I atttach a piece of metal paning where the 2 return ducts will enter the cavity to deflect the air downwards? I could screw it into the wall, so when air hits it, it will slide down? Or will the air just naturally hit the wall perpendicularly and be sucked down into the return plenum.
This was hard to explain but is really quite simple-not a job for a pro to waste his valuable time.
again, I knowe it is not ideal, but at least there will be 2 sealed runs from the bedrooms rather than nothing as before. BTW, I sealed the cavity very, very well.