Your air conditioning installation is designed to keep you cool and comfortable on hot days, so anything that prevents your AC from functioning efficiently will be getting in the way of your comfort. If the air coming out of your air supply vents or registers is warmer than you'd like, here are some likely suspects:
One of the things that can undermine your AC system's cooling performance is leaks within your HVAC ductwork. Over time, your ductwork may wear and tear due to normal operating conditions. Pests such as rats and mice can also nibble the ducts running in your ceiling, basements and other areas in your home, leading to loss of conditioned air.
It is advisable for homeowners relying on ducts to keep their space cool on hot days to have their ductwork inspected routinely by a qualified HVAC technician so that any leak spots can be identified and sealed properly.
Insufficient amounts of refrigerant.
For your AC to operate at optimal efficiency, it needs to have the right amount of refrigerant. Refrigerant is what absorbs heat from the hot air going into the AC system through the return air grilles. Unfortunately, refrigerant can leak out of the AC system or it can reduce due to normal running of the system.
If there is a drastic decline in your AC's cooling performance, then it could be that your unit is running low on refrigerant. Preventative maintenance of your AC system can help locate and seal leak spots in your ductwork. It can also help keep tabs on your AC refrigerant charge, so that more refrigerant can be added when need arises.
Another common reason as to why your AC's cooling ability may go south is when your unit's filter is too dirty. Your AC's filter allows for proper flow of air within your AC system by filtering out airborne dirt particulates that may enter the system. If it is left to become clogged with dirt, it will be less efficient at its job.
Not all the problems that reduce your AC's cooling ability are system-related. The presence of air leaks in your walls, ceiling and around window and door frames can also significantly contribute to cooling inefficiency, as it will result in loss of cool, conditioned air. So, make sure to seal the cracks on your masonry walls and caulk the gaps around your window and door frames in order to make your house airtight.
With these factors in mind, you should be able to come up with a proper plan geared towards optimising the cooling performance of your AC system.