I'm dividing my house and want to allow the new tenant some ability to control their space. The HVAC system is operating and scaled for the entire (pre-divided) square footage. Can I add another thermostat to control the part of the house that doesn't have a thermostat?
Thanks, Gary

It's called zoning. How difficult it is to do depends on the existing ductwork. Controllable dampers have to be installed as well as a zoning panel.

Some thermostats have different levels of security. e.g. max set point.

Here is some info: http://www.zonefirst.com/products/DesignManual.pdf