[jchoo]

Does each room that has forced air must have a return air?

[hvac1000]

Does each room that has forced air must have a return air?

Not in the room itself. But it must have a way for the supply air to get back to the return. Sometimes the doors are cut off on the bottom a inch or so to allow the supply air to be sucked back to a central hall return air.

The more return air duct you run the more it costs for the system to be installed. Well designed systems will usually have a return in each room but that is not always the case. My home here uses a central return air for all 3 systems. Each of the 3 central air units has its own air handler and return air filter grill. The system works great and the doors are cut off on the bottom about 2 inches but since the returns are in the hall that the doors connect to a return air in each room would have been unnecessary and very cumbersome to install.

So the answer is no unless a specific code in your area requires one in each room.

[ma0641]

It is better for air flow but not required. My log home has 1 large central return.

[jchoo]

I'm adding a sunroom right beside my kitchen which doesn't have a return air. The sunroom is open to the kitchen