How many zones do I need? Generally speaking, there is a limit to the number of zones that can be installed in any given house. At least there is a limit to the number of zones that make since for a house. First of all, unless you are working with a home that is larger than 2500 sq. ft no more than 4 zones are recommended. In smaller homes (less than 1500 sq. ft) no more than 2 zones are recommended. A zone can be one room or a whole wing of the home. A two story house could have an upstairs and a downstairs zone thermostat. If you are replacing a system, simply count the number of thermostats you currently have.