I own a house that was built in 1918. It has been renovated over the years and I am finding some of the renos strange. My question is about the ducts. Drywall had been put up over the plaster walls and a hole was cut out for the vents. Over the cutouts were placed air return registers, I imagine because it was a simple fix. My biggest concern is how the air is being directed out from the wall. For example two bedrooms upstairs share one heating duct but the duct seems to end at floor level and then there is just wall cavity. Nothing directing the air out to the rooms. There is nothing to stop it from blowing up into the wall. Can this be fixed and how?