How do you zone a forced hot air heating system (furnace)?
Standard split system with AC for summer and with ducts that are connected to the one system and only one thermostat on the first floor. Problem being that the 2nd floor doesn't get warm enough before it goes off.
Most zoned systems incorporate the use of additional thermostats and either vacuum or mechanically operated dampers installed with in your existing ducts and trunk lines. This can be added to any ducted systems by installing the dampers on the supply side of the distribution to the rooms you would like to zone. The thermostat installed in that room will allow the furnace to continue to run until the temperature is achieved without over heating the other locations. A properly design zoned system will reduce the overall energy consumption since you are only heating or cooling the required locations. When install zoned system with a new heating and cooling system, the size of the system can be also reduced thus lowering the up front equipment cost. Look into an Arzel Zoned System. It is a commercially available system which works on a vacuum damper system and communicates with most manufactured furnace on the market today.