During the summer, the upper-story rooms are likely to be much warmer than the main areas of the house if you live in a two-story house.
Changing the thermostat can cause an imbalance that results in the lower levels becoming too cold and resulting in high utility bills.
A hot roof, hot air, or leaky ductwork can cause warm upper floors. The hot air rises, while the cool air settles at the bottom. A home with multiple stories will have adequate cooling on the ground level, while heat will gather in the rooms up above. The roof can absorb radiant heat from the sun and radiate that heat into the rooms closest to the attic. For the cool air to reach the upper floors of the house, it must travel through longer sections of ductwork. This can make cooling these rooms even more difficult if there are leaks in the ductwork. There is no need to replace the entire AC unit in order to achieve a balanced cooling in your home. Instead, you just need to replace the AC coil. There is nothing more you need to do but adjust the dampers in each room by opening the basement and ground floor registers a bit less, and as you go up, opening them up a bit more. Making sure the air filter is clean and replacing it if needed can also help ensure proper airflow. Radiant heat can be reduced by installing enough insulation on the roof. The roof deck or the roof floor can be installed with insulation, depending on the roofing style. Adding mechanical ventilation to the roof can boost attic insulation. Finally, if there are issues with the HVAC system itself, such as low air conditioning output or leaks in the ductwork, you must have it fixed by a professional HVAC technician.