The return "ducts" in my house are run through building cavities, and I've just about had it dealing with them.
I do have a laundry chute to sacrifice. I am toying with the idea of using that space for a single, large return duct; which would have grates on the first and second floor (and maybe a smaller one in the basement where the furnace is located?).
That way, my entire HVAC system would be ducted, and I could have some hope of actually sealing it. I am also not above putting vents in the doors, so that there is still air circulation when the bedroom doors are closed.
So my options: (a) Continue with the building cavity "ducts". This sucks because they seem to be returning air from just about everywhere except where they should be (e.g. pulling air through fiberglass, making it dirty and moist; pulling air from the garage because it's not sealed correctly) and so on.
(b) Seal off all of the existing return cavity "ducts" and have one massive duct that takes the place of the laundry chute (it looks like I have room for a 16x16" duct in there). It would have two or three large grates on it. Rooms with doors might have some form of grate added to allow airflow with the door shut.
My question is: which option is less bad? Is this a valid solution?