A core is a vertical area in architecture that is utilized for circulation and services. It is also known as a circulation core or a service core. Staircases, elevators, electrical cables, water pipelines, and risers are examples of fundamental components. The term can also refer to the space within a building where these elements are located. Cores are essential in buildings greater than one floor high, because they provide areas where people can go about their business while waiting for lifts or escalators, and where deliveries can be made without walking through public spaces. They also provide places where utilities can be housed and controlled. In low-rise buildings, cores may be omitted if there are sufficient supply lines brought up to the roof in order to reduce construction costs. In high-rise buildings, especially hotel towers, cores are important factors in reducing overall weight, which is good for design stability and energy efficiency. Core volumes should be designed with care to avoid making things too heavy or bulky for the structure. Heaviest items should not be placed in the core, but rather distributed throughout the building to minimize the amount of material needed. This is particularly important in tall buildings, where weight increases as height increases. The core of a building is where the majority of its mass is found. This means that any damage to the core system will have a major impact on the performance of the building.