Rooms Missing Return Air Vent

Our Answer

Not all homes have return air vents in every room. In fact most forced air heating and cooling system use one or two centrally located return air vents, typically in a hallway or other space central to the home.   You mentioned that some rooms have registers that do not appear connected to the HVAC system. These may or may not be return air vents. It’s a bit difficult to tell, but here’s an easy test.  Make sure the HVAC system is running full blast (i the summer, you can simply turn the thermostat all the way down and visa-versa in the winter).  Then take a tissue and hold it against the return, then let it go.  If it stick to the register, then this is in fact working as a return.  The tissue helps you spot airflow back into the uct system.

I have also seen registers used to simply circulate heating or cooling from the room above or below without being connected to the HVAC system.

As for your question about the 3″ ducts, you may be referring ot a SpacePak HVAC system.  This is a small duct high velocity system which is popular when retrofitting older homes as the ducts can be run inside existing wall cavities with very little damage. it is not a solution for a home that has inadequate return ducts.  If that is the case here, you be better off running a new central return duct. Air will naturally be drawn back to the return from the rooms you mentioned.  Just make sure there is a 1″ gap under the door to the room.

However, despite everything I have told you, I dont know what the problem is you are trying to solve.  If rooms are too hot, or too cold, for example, there may be another solution entirely.  Comment below with any additional information.