The ideal household temperature for a middle aged healthy adult is between 68 and 72 degrees F. If you are looking to save on heating costs, as low as 62 degrees F may be tolerable as long as you are dressed appropriately in layers. This does not mean a jacket is required but a shirt and sweater.
72 is considered "room temperature." All other answers are made up, taken from irrelevant sources, or culturally misleading. In the United States, room temperature is 72 degrees.
The "ideal" temperature is whatever temperature feels most comfortable to you. Some people prefer warmer temperatures, and others prefer colder. Personally, I keep my thermostat set at around 70-72 degrees.
