I was shocked the other day when I took the vent cover off of, what I thought was a heat register in my residing room. I figured that I should vacuum out the vents before I turned on the heat for the first time. I was new to the house plus this would be the first winter season season residing there. Imagine my surprise when I realized that there was no duct labor there. It was easily open to the other side of the wall where there was an identical vent cover. I thought at first that someone just put them there for decorative purposes but when I asked the landlord about them he explained that the vest covers plus pass through were to allow for chilly air return. The heat came from the vents in the ceiling plus it was drawn down by the chilly air returns. The air was then sucked back into the furnace to be warmed again. This natural flow of hot plus cool air allowed for even heating. Years ago, before Heating, Ventilation, plus A/C systems were installed, they used floor vents plus wall vents to circulate the hot air throughout the house. It is still used in many areas where it is impossible to install new equipment. Warm air rises, cool air falls, it is just the nature of things plus if you can use this process to deliver you an even hot temperature, this is all the better. If you have efficient, “drafting”, as it is called, you can easily save a lot on your energy bills too.