A high efficiency heating and cooling system does not end with the unit itself. This is especially true in Phoenix, where most of the ductwork is located in attic space where temperatures can reach 140+ in the summer. A high SEER AC unit is definitely an improvement when replacing older units, but that air needs to be carried through the ductwork distribution system to keep you comfortable in the winter and summer.
If the air conditioning contractors cut corners on the ductwork, then the entire efficiency of a new unit is greatly reduced. In Phoenix, homes built after 1980 used flex ductwork as the preferred means of air distribution. Flex ductwork is good because it is easy to install, required little preparation and can be done by less skilled workers. On the down side, unless an air conditioning contractor does a proper load and duct design calculation using Manual J and D, a number of problems can arise because of cutting corners. Problems such as poor airflow, high room pressures, excessive dust and conditioned and heated air being lost to the outside are all too common in existing homes. Many times if an air conditioning contractor has done work or replaced an AC unit in the past, they really will mess a system up. I think one of the reasons good home inspectors and energy auditors are so skeptical of HVAC contractors in Phoenix is because we see the outrageous work done and what it is costing the homeowner.
Duct leakage can mean your heating and cooling system is sucking outside attic air into the unit and heating it in the winter or cooling it during the summer and blowing air into the attic on the supply side. Both are costly and will decrease the life of the unit. APS estimates that an average 15% of a home’s existing air is wasted to the outside. SRP shows similar statistics and both utility companies sponsor home energy audits to check for leakage and offer rebates for sealing the ductwork. For more information on duct leakage visit:
