If a house has one thermostat that controls the heating and cooling for the entire structure, it has one zone. If the house has more than one thermostat, each thermostat is controlling a selected area or zone. Zoning offers more control over the comfort of the entire space.
The benefits of zoning depend on the size of the house, the style of construction, and the type of system. A 1000 square foot ranch may not be cost effective to zone for forced air heat, but would be efficiently zoned room by room with electric heat. A cape with a small second floor would be difficult to zone with a forced air system, but easy with hot water baseboard.
There are two common ways to control the comfort of a home. One way is to install separate systems for each area, allowing each area to be independent of the other for heating and cooling demands. Another method is to use one piece of equipment and create zones. A forced air system uses a control panel and motorized dampers working in separate trunk lines to make comfort zones. A hot water system uses zone valves or circulators feeding individual loops to form individual comfort zones. Zoning is ordinarily use to separate sleeping quarters from living areas, or first and second floors. Multi-level structures have different demands on each level, and zoning increases the comfort control. In a central system using one unit for heating and cooling, the full output of the machine can be directed to each zone to deliver maximum capacity when needed. This means that a house cooled with one four-ton system can have all four tons delivered to each zone. The same house cooled with two 2-ton systems can only deliver 2 tons of cooling to each zone.