Most homes in the Unites States will have either one or two HVAC systems, while some very large homes will have three or systems. A system includes an indoor air unit as well as a condenser, which is located on the exterior of the home. The number of systems depends upon several factors including the size of the home and the layout.
A qualified HVAC contractor will make a series of calculations to determine the heating and cooling load on the home, while looking at the insulation, windows and doors, which factor into the heat gain and loss. The results of these calculations, as well as the requirements of the building and mechanical code, will determine the size of the system. Once the size is determined, the HVAC contractor will then determine if a one or two zone system will be required, based upon the load and the layout of the home. Often, while it is possible to use a single system based upon the heating and cooling load, the layout of the home, as well as the structural design, prevents the HVAC contractor from providing heating and cooling to all parts of the house.
The HVAC contractor will install the most efficient system in your home to meet the heating and cooling needs. This design will be the most economical to install as well as the most economically to operate. As a homeowner, there is not need to worry that a single zone system is inferior to a two zone system!
