I have a two story home that has two units. The first floor has one return and the 2nd floor has two returns. Since moving into the brand new home about 2.5 years ago I have never been able to cool the 2nd story below 79 degrees during the summers except at night. Builder sent contractor out to balance and adjust vents but still no help. They attributed it to full sun and lack of shade. Last week I had a local company come out to inspect units and they found that one of the returns on the 2nd floor unit was not connected to the ductwork. You can remove the filter and turn the light on in the attic and clearly see into the attic. There is ductwork coming from the unit but it stops about five feet short of the return grill, sucking in 105+ temp back into the handler. How in the heck did it pass the original inspection is beyond me. Tech took temp reading at this return and got 98 degrees. Called builder to see if they would come out to fix problem and they had someone call me from their installer and they said sometimes they install units this way but they would send a tech out to take a look. My question is has this possibly damaged my unit by making it run more than it should have? Also is it possible that we have been exposed to insulation particles and pesticides being brought back into the system? What recourse do I have with the builder?