If you use a furnace or heat pump to warm up your house, the heated air travels to the various rooms through ductwork and then out vents. Most vents have levers on them allowing you to adjust the louvers behind the grill. This way you can direct which way the air flows when it first comes out of the ventilation system. In fact, you can adjust the louvers to lie flat, shutting off the ventilation opening.
Does this mean that you can shut off airflow into an unused room by doing this? And is this a way to effectively reduce energy costs during the summer?