The ducts that are installed for your HVAC system usually have insulated covers. If the ducts are not insulated then it is important that you consult a HVAC technician to get it properly insulated. There are many HVAC companies that would offer you the service. Check their credentials before hiring them for the task. An insulated duct prevents conditioned air from leakage hence increasing the efficiency of the unit. If the ducts are not insulated then your air conditioner will overwork which will even affect the durability of the unit. Sometimes it will also damage the unit beyond any repair that you will have to discard it and replace it with a new one in order to avoid incurring such losses. Even if the ducts have insulation it has to be checked once in a while to see to whether the insulation has worn out or not. If on checking you find out the insulation has worn out then call a HVAC company to replace the insulation.
If there is no proper insulation then the air will start leaking through the vents putting more pressure on the HVAC system to work continuously so as to cool to the desired temperature set on the thermostat. Now is the best time to check the insulation and get it fixed by a HVAC technician. When the HVAC system functions more then it will start consuming a lot of energy thus increasing your energy bill. You will have to bear all these extra expenses until you get the insulation done properly.