If your house has only central air return grille then you will notice that the return air will struggle in order to find a way back to the furnace. As a result, the pressure in each room will vary and you’ll experience uneven room temperature. This problem may also cause moisture build-up in ceilings and walls, not to mention contribute to high energy bills!
Having a single air return grille is not effective because it wouldn’t be capable of conveying the air back to the furnace effortlessly so that it can be re-heated. After all, a single return-air grille will face a lot of pressure as it has to serve the entire house! Thus, it causes a break in the loop and prevents the furnace from functioning optimally.
In most cases, if the doors of the room are closed then it would be impossible for the central return-air grille to pull in air. Because of the fact that the living room and the hallway are depressurized, due to the lack of new air to pull in or air returns, the return-air grille would attempt to pull in air from the attic into the hallway via the cracks present in the ceiling. While this is definitely disadvantageous, it becomes a double whammy as the air from the attic is cold, which in turn increases the heating load of the furnace.
Does Every Room Need Air Return Grilles?
While it is a myth that air return grilles are required in each and every room in the house, it is definitely necessary to have more than one of these grilles installed at strategic places in the house. The most important place to have these would be the bedroom. You should definitely ensure that there is an air return grille which connects the bedroom to the hallway adjacent to it. Likewise, you can also install these in rooms that have a high footfall or usage in the house.
In order to resolve the problem of room-to-room pressure imbalance, it is necessary to have air return grilles properly installed around the house.