Re: How to equalize the temperature in your house and save on energy cost.
marjorie .... actually in this case the configuration of the return vents lower down is more beneficial during the heating/cooling use.
the vents doing the heating and cooling are in the ceiling.
Unfortunately that type of system is almost counter productive for a heating system
Since warm air rises most of the heat will be near ceiling level and it's difficult to push this air down. Having the vents lower down in this case helps to draw that warmer air downward.
The term "cold air return" is for that reason to draw the cooler air from the floor level and return it to the furnace to be heated. If the return ducts are at ceiling level this will draw warm air returning to the heating system.
However .... the configuration you have lends itself to be advantageous for cooling.
Cool air settles downward and takes less effort for the HVAC to provide the desired comfort. Since the warmer air is higher in the room ..... the cool air falling from the supply vents in the ceiling cools this warm air on it's way downward.
For both heating and cooling having the return vents lower down will create turbulence to mix the air which helps making the temperature more comfortable.
The method .... asc2078 describes .... of having 2 returns ( 1 high and 1 low) is advantageous if the HVAC is located in a basement.
For this type of HVAC arrangement the advantage of warm air rising for heating requires less effort to supply heat to the living spaces.
Warm air from the heat vents located in the floor will rise toward the ceiling leaving cooler air settling down toward the floor.... the law of nature.
In this type of heating system the cold air return should be at floor level. That's not to say in the floor but usually they will be mounted on a vertical wall at floor level ...... for the same reason mentioned earlier ..... to draw the cooler air from the floor level and return it to the furnace to be heated.
The other reason to have the cold air return vents down toward the floor level is to help with circulating the heated air coming from the warm air heat vents.
Since warm air rises you don't want all the warmth at the ceiling .... most people don't live on the ceilings .... you want it at the level of the room where you are.
This helps preventing stratification where you would have a cold zone at floor level then different layers of warmer air rising with the warmest being at the ceiling.
For this configuration of HVAC it takes more effort to move cool air for A/C.
Since cool air is more dense and wants to settle lower down in the room .... having the return located higher will help with drawing the warmer air located higher up and the turbulence will help mix the air better.
Most (99%) commercial spaces I see are poorly configured for HVAC air flow and really inefficient ... in my mind.
When we leave the blower fan on at work all we get between the a/c cycles is warm air. ugh.
Usually they will have the supply and return venting in the ceiling and in cases only 6 to 8 feet apart.
Many offices I visit will have have similar complaints of one area will be boiling and another area will be freezing while the A/C is on. The opposite of one area freezing and another area boiling with the heating on.
Just some thoughts.
"" an ounce of perception -- a pound of obscure "