need help with return ducts

[robjamell]

I have moved into a new office with drop ceilings. Each of the 5 offices/rooms and the one shared hallway all have ducts that air comes out of, however the only form of return air is grates in the ceiling.

I have been told that this is very inefficient because I am now heating/cooling the air above the drop ceiling. I have no extra dollars to play with and the landlord is not willing to do anything as he said this is standard practice. Not willing to argue, I am choosing to do this myself.

The current roof unit just has a large opening going through the roof. I have been told that the best way is to go into a manifold and have a flex duct go to each room. I have also been told that I can just run one main duct to the hallway and that will be not as good but much improved over using above the ceiling air.

I need opinions and I need to know what info you guys need in order to tell me what size flex duct/ducts I will need.

Thank you in advance.
Rob

[fearlessfurnace]

do not think we can give a good answer without being there. first thing I think the single return option runs into trouble if you do not open the rooms to the hall. If the air has to jump above the cieling from room to hall you are heating the space above the cieling.

[robjamell]

All the rooms that have doors are left open at all times to the hallway.

I will be happy to draw or take any dimensions necessary for the help.

Rob

[fearlessfurnace]

I think we are straying into the forbiden DIY zone.

[robjamell]

I am sorry. I assume this forum is NOT for DIYers?

BTW - I have ran flex duct, built manifolds, etc. before I just don't know the airflow part of things.

[tinner73]

it's called a plenum ceiling and it is very common. i'd leave it alone.

[robjamell]

Thank you. I am aware that it is a plenum ceiling.

My problem is that the air above the ceiling is an extreme temp difference.

[energy star]

A plenum rated ceiling would cost more to construct would it not?

[tinner73]

Thank you. I am aware that it is a plenum ceiling.

My problem is that the air above the ceiling is an extreme temp difference.

how extreme?

[stone-cold99]

Like Tinner said leave it alone.

[robjamell]

35 degrees difference

[tinner73]

since you didn't take the 10 seconds it takes to fill out your profile..i don't know where you're from.

are using heat now?

[robjamell]

Philadelphia suburbs