Zoning is crucial in large homes, with central heating (and cooling) systems. Zoning can provide important energy savings.
The number of zones and the design of zoning
Manufacturers are offering sophisticated zoning systems, some of them able to handle up to eight temperature zones or more. Zone controlled systems
= Room by room heating and cooling control.
But, unless in exceptional cases, you will not need more than two or three zones (bedrooms, living room, rooms infrequently used...).
All depends on the size and layout of your house, and your choices, but more than three zones can make the system unnecessarily complex to install and to use. And you may not get any benefits.
The energy savings
The energy savings and the effectiveness of temperature zoning with central HAVC systems vary a lot. Manufacturers are actively promoting their systems, but energy savings depend largely on the type and size of the house and its insulation and design.
You may not need temperature zoning in very energy efficient homes. Their design and insulation levels provide consistent temperatures. They may not need central heating and cooling systems, and zoning...
Typical zoning systems involve multiple thermostats, wired to a control panel, which in turn operates automatic dampers within the ductwork, or the valves on hot-water radiators and baseboards.
The thermostats will constantly read the temperature of their specific room, and will open or close the dampers (or valves) according to the thermostat's settings.
Anyway, if you don’t set them at the right temperatures, or if you don’t have sensors to switch them on and off according to the occupancy of the rooms, energy savings will not be significant.
It’s easy to squander energy, even with zoning. If you set the heating temperatures of the different zones too high, zoning will not help much.
See: Thermostat Guide for Energy Savings The type of heating system is critical for zoning. Single speed furnaces will not respond smoothly to the heating needs in the different zones and will squander energy. You need a multi-speed system…
Dampers and valves
The use of zoning with central ducted systems requires a system of dampers (furnaces…) or valves (hydronic systems).
Manufacturers are offering different types of dampers and valves with their heating and cooling equipment, but there is also manufacturers making them for existing heating and cooling systems.
Prices and manufacturers
Zoning an existing heating system can be relatively cheap... or moderately expensive. The system in itself – the control panel, the dampers/valves, the thermostats – may cost, say, $1,000 - $1,500 (for a two or a three zones). But plumbing, insulation and sealing can make the upgrade a lot more expensive - especially if it also involves new doors, to separate the different zones.