Originally posted by jramunni
Is the main duct and bransh duct exposed (accesible)?

Our typical damper install is an insertable damper in each (accessible) branch run (5",6",7" round).
If the branch runs are not exposed but the main trunk is, or can be, we have dampers that are inserted up through an opening cut in the main duct below each take-off and lock them selves in place just past the take off in the round duct. Our third damper option is in the register boot with the air tube run throught the branch duct and accessed in the main trunk. The concern with the 3rd option is air noise (whistling)when the damper is closed being that you are now dampering in the room with a louvered damper.
For many homeowners "Comfort at Last" is more important than a little noise from time to time.

After the main duct leaves the utility room, it and all its branches are enclosed by floor above and ceiling below. To access each branch would require a hole through the ceiling. Each branch is rectangular, 3 1/2 inch by 8, 10, or 12 inches.