If you are in the process of buying a new home or even remodeling your existing home, then this is the time to consider the placement of your central heating and air conditioning vents (otherwise referred to as ‘registers’). Most vents are located in either the ceiling or even in the floor for homes that are equipped with basements.
The optimal location for a vent in a room with a single vent is on the interior wall (farthest away from the outside wall) and pointing towards the outside wall. The idea is that the extreme temperatures from outside of your home will be most pronounced along the exterior wall. By locating the vent as far from the exterior wall as you can and then pointing the vent at the exterior wall, the air from your air conditioning unit flows along the ceiling or floor and then up or down the exterior wall which will maximize the impact of the cooled or heated air within that room.
If you are involved in new construction or remodeling, then the other factor you have to take into account is the supporting duct work that feeds into the vent. If you identify the optimal location for your vent and then find that there is an obstruction that prevents you from placing the vent in that exact position, then try to get as close to there as possible. A few inches in one direction or another will not cause a significant lapse in efficiency. On the other hand, if you can place the vent where you want to but in order to do that you have to route your duct work in such a way that you have to add another 10 feet or so, then the efficiencies you will gain by the new duct placement will be lost in having to run more duct than normal.