The California Green Building Standards Code (CALGreen Code) is Part 11 of the California Building Standards Code and is the first statewide "green" building code in the US. Background and purpose The purpose of CALGreen is to improve public health, safety and general welfare by enhancing the design and construction of buildings through the use of building concepts having a reduced negative impact or positive environmental impact and encouraging sustainable construction practices in the following categories: Planning and design Energy efficiency Water efficiency and conservation Material conservation and resource efficiency Environmental quality To achieve CALGreen Tier 1, buildings must comply with the latest edition of "Savings By Design, Healthcare Modeling Procedures". To achieve CALGreen Tier 2, buildings must exceed the latest edition of “Savings By Design, Healthcare Modeling Procedures” by a minimum of 15%. The provisions of this code are directed to: State-owned buildings, including buildings constructed by the Trustees of the California State University, and to the extent permitted by California law, buildings designed and constructed by the Regents of the University of California and regulated by the California Building Standards Commission. Energy efficiency standards regulated by the California Energy Commission. Low-rise residential buildings constructed throughout California, including hotels, motels, lodging houses, apartment houses, dwellings, dormitories, condominiums, shelters for homeless persons, congregate residences, employee housing, factory-built housing and other types of dwellings containing sleeping accommodations. Public elementary and secondary schools, and community college buildings regulated by the Division of the State Architect within the California Department of General Services. Qualified historical buildings and structures and their associated sites regulated by the State Historical Building Safety Board within the Division of the State Architect within the California Department of General Services. General acute care hospitals, acute psychiatric hospitals, skilled nursing and/or intermediate care facilities, clinics licensed by the Department of Public Health and correctional treatment centers regulated by the California Office of Statewide Health Planning and Development within the California Health and Human Services Agency. Graywater systems regulated by the California Department of Water Resources and the California Department of Housing and Community Development. Land use In US urban land area quadrupled from 1945 to 2002, increasing at about twice the rate of population growth over this period. Estimated area of rural land used for residential purposes increased by (29%) from 1997 to 2002 (2002). Water use Water is a precious natural resource. At least two-thirds of the United States