A primary residence's most common story configuration is two-floor house plans (also known as "two story house plans"). The main living spaces (living room, kitchen, etc.) are located on the main level of a traditional two-floor house plan, while all bedrooms are located upstairs. A more modern two-story house plan places the main bedroom on the main level, while the children's and guest rooms are located upstairs. 2 story house plans can save money by reducing the size of the foundation and are frequently used when building on a sloped site. Two-story house plans typically have less roof area than single-story plans, making them more energy-efficient, especially in colder climates.