In the below picture you see my doorway to the left which goes into an addition that was put onto my house 10 years ago. That wall use to be the exterior of the house with a huge window that was boarded up as you can see. Below it was a cold air return. I had an LVL installed and we took that wall out.
Below you see i circled another cold air return in yellow that was put into the wall when the addition 10 years ago was done. The red line is where the only heat register in the 10 year old addition is. The green circle is the cold air return I want to eliminate as its right in the middle of my living room floor.
To the left of this room are 2 bedrooms, each with 1 heat register and neither has a cold air return.
About 5 feet behind me is another heat register and the opening to my small 12x12 kitchen which has a large heat register and another large cold air return. ( I can provide pictures tonight if that helps)
So what I want to know is if the yellow cold air return is enough for the living room, or do I have to put another cold air return where the blue rectangle is?
Last piece of info to tell you is that the original cold air return in green runs between the floor joists and there is metal sheeting nailed to the bottom to act as a duct. This duct however does not run back to the furnace, instead it runs 14 feet under the living room floor between the joists where the sheet metal suddenly stops, and there is a large 2foot by 2foot opening between the floor joists where the air then combines with the basement air.
When the furnace turns on, lots of air is sucked through the living room floor where this register was, but its just getting sucked from the living room into the basement, is this normal for a house built in the 1900s and then retrofitted with a newer hvac system? The yellow in wall cold air return and the one in the kitchen both are ducted back to the furnace.
I have been told my furnace is a high efficiency one that vents outside through pvc, I was reading about dangers with backdrafts with negative pressure in basements by sucking the cold air return "from" the basement instead of the living space of the house.