Some fancy houses have electronically controlled dampers that shut conduits on and off, depending on room temperature.

For houses without this fanciness, there are manual controls on each register/vent that you can open or close to adjust how much of the temperature-controlled air comes into the room.

Newer thermostats will turn things off or adjust the temperature up or down when you leave the house. This saves a lot of energy. The other nice thing is that these thermostats can be programmed to pre-cool or preheat the house just before you get home from work/school.

Some larger houses have an upstairs AC unit and a downstairs unit.

Houses in the northern United States often have wood-burning, stoves, fireplaces, or heated flooring.