I was performing a home inspection on the West side of Houston when I came across a method of creating air flow in rooms that was a bit unusual. I thought that I would share it with you as a continuation of part 3 of this series, but I am not sure that it really works too well. My simple test did not show much air going through it.
I noticed that there were a lot of return vents when walking through the rooms then in the hallway. Pictured below is two large returns in the hall, and then below that is a picture of a room. On the ceiling of the room, you will notice two vents that use a cover typical for registers. One is a register, while the other is meant to be a return.
Great, I thought. They have no ceiling fans in this house, so they are trying to get the air to flow by using ducts attached to the return plenum in each room. I noticed that one of the hall returns did not have a filter in it, and this should have been my first clue to its true purpose. I then go up into the attic. While wandering around, taking in the sights, I find two plenums above the returns in the hall ceiling, but something looked off.
I checked the duct work to see that the ducts from one return were going to the return plenum on the HVAC system, but the other plenum had ducts going to the returns in each room. I wondered if this could work. The drawing below is demonstrating what was meant to be happening.
The air goes through the returns in each room to the vent in the hallway. When the return in the hallway draws air, it is meant to suck air from this vent connected to the room returns. They could have hooked those ducts up to the plenum created for the return air since it was right there.
I took some tissue paper to the returns in the rooms to see if there was any air movement when the air conditioning came on. There may have been a little, but the tissue was not pulled by any suction, like it was at the actual return. This method may cause some air to move, but I doubt that it helps much. I would just take the fake return ducts, and attach them to the return plenum.
Note: Shortly after being told that this system was to improve energy efficiency, I found the actual intention of this design. It is not for air flow back to the unit, but rather to equalize pressures in different parts of the house. It is called a jump drive.>/p>