We have rooms that are too hot or too cold in the summer when the air conditioning is running, and the same thing in the winter when the furnace is on. The rooms that are tool cold in the summer are too hot in the winter. I figured it had something to do with the air flow in the rooms, but I was not sure how to fix it permanently. I called for HVAC repair in NYC for a tech to come and figure it out. I was adjusting vents in the rooms and the dampers on the ducts to no avail. It was getting frustrating. I would take a room that was too cold and make it too hot. Then it would be too cold again when I tried again. If I made the hot rooms cool, then another room that was normal would get too warm.
The technician found two problems with our system. The first was that both the central AC unit was not big enough for our house. I bought it used and had a friend install it. The units are measured in tons, and our system was about a half ton too small to work on our house before we added the addition. Now it was even worse. Our furnace was barely adequate for the house, but good venting and touching up some insulation in the older part of the house would fix that.
The other problem was the vents. We needed a zone control HVAC system because of how our house was laid out. The additions gave it an odd shape, and there were open areas, hallways and large and small room to heat and cool. The tech said that it sounded worse than what it was. They could use most of the existing ducts, but a couple of return air vents would definitely need to be installed. The zone system and new AC unit has us very comfortable. I actually added the insulation myself to save some money on the upgrades.